Anti-seasonal flooding drive substantial alterations in riparian plant diversity and niche characteristics in a unique hydro-fluctuation zone

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However, the effect mechanism of anti-seasonal hydrological alterations on vegetation distribution patterns and niche characteristics in the water level fluctuation zones (WLFZs).is still unclear. In this study, 368 quadrats were selected to investigate the effects of the anti-seasonal hydrological regimes on the foristic composition, species diversity and niche characteristic in the hydro-fluctuation zone of the Three Gorges Reservoir (TGR), a unique riparian ecosystem, China. The results showed that the number of species per square meter (S), the Shannon-Wiener diversity index (H) and Simpson dominance index (D) of the plant guilds in the TGR increased significantly with elevation, which was inconsistent with humped diversity–disturbance relationship of the intermediate disturbance hypothesis, while the opposite trend was observed for the Pielou evenness index (E). The H, D, S and E from upstream to downstream firstly showed a significant increasing trend ( p <0.05), reached the highest in the middle reaches, and then decreased in the lower reaches. The vegetation was classified into 12 guild types but the vegetation composition showed a significant variation with a transition from xerophytes to mesophytes and hygrophytes with the increasing flooding time. Cynodon dactylon was the most dominant species based on its highest important value and niche breadth. And high niche breadth had a high niche overlap between species. Therefore, anti-seasonal hydrological alterations precipitated substantial reduction of plant diversity, species competition and exclusion among species by expanding the niche in the guilds. The vegetation in the unique riparian ecosystems was still in the primary stage of plant community succession with low species diversity, high niche overlap, intense competition and obvious single-species dominant communities. Compared to total nitrogen, total phosphorus and soil organic matter factors, the hydrological alteration filtering was more important in explaining the plant guild patterns and niche characteristics. Therefore, there may be some differences in the governance strategies adopted in different areas of the novel riparian ecosystems for vegetation restoration efforts of the riparian forests. Anti-seasonal flooding Species diversity pattern Niche characteristics Plant guilds Riparian ecosystems Three Gorges Reservoir Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 1. Introduction Global warming and anthropogenic disturbance such as dam constructions are associated with an increase in flooding events, making many ecosystems worldwide vulnerable to submergence and flooding (Pucciariello & Perata, 2012, Xiao et al., 2022), which are major abiotic stresses for plants as significant determinants of plant species distribution worldwide, functions of plant guilds, forest community composition, structure and dynamics (Jackson & Colmer, 2005). Hirabayashi et al., (2013) also reported that a warmer climate would increase the risk of floods. What’s more, alterations of hydrological regimes and floods owing to the joint effects of operation of reservoirs and warmer climates play an important role in regulating the foristic composition, species diversity patterns and niche characteristics of riparian forest (Jian et al., 2017; Su et al., 2020). As the floodwaters move onto the riparian area, the soils became hypoxic, even resulting in severe anaerobism for plant roots, which posing a threat to the distribution of riparian forest plants without specific traits to adapt to anaerobic condition and ultimately lead to plant death (Gibbs & Greenway, 2003). Consequently, the unnaturally flooding (winter flooding) and prolonged inundation duration (nearly half a year) would remarkably influence the plant guilds, the plant community composition, species diversity pattern, niche characteristics and patterns of resource utilization of riparian forest. And plants growing in riparian zones are essential indicators of the ecosystem stability of riparian habitats. Therefore, it has crucial ecological significance to evaluate influences of anti-seasonal long flooding on the plant guilds and niche characteristics of plant communities in the newly formed aquatic–terrestrial interface for vegetation restoration and reconstruction in the riparian forest. However, the response of riparian vegetation by the niche characteristics to such unnaturally continuous flooding environment is less documented. To understand resource utilization status and ecological adaptability of various plant populations in different environments and provide references for biodiversity conservation and vegetation restoration efforts in degraded riparian forest ecosystem, the niche theory were introduced and has become one of the fundamental theories to explain species coexistence and competition in natural plant guilds (Slatye et al. 2013; Cui et al., 2013; Jian et al., 2017; D’Andrea et al., 2020). Niche involves two complementary aspects. one relates to the space occupied by a group of species or a guild in the ecological space and the other relates to resource utilization and competition among coexisting species (Lakkis, 1994). Niche breadth measures the range of resource characteristics across which a species exists, and indicates the extent that species utilize different types of resources. Niche overlap has often been used as a measure of potential competition between species (Milne & Mason, 1990), because it is expected to determine how many and which species can coexist in a guild. Previous studies found that species with similar patterns of resource utilization (i.e., species of the same guilds) were susceptible to competitive interactions that affect the community structure (Pérez-Crespo et al., 2013). Patterns of resource utilization (either food or habitat resources) were normally analyzed in the framework of niche theory, i.e., members of the same guilds similarly exploit similar resources and may be underlying competitors. It is generally agreed that the number of related species that can coexist in a given community depends on the niche widths of the several species and the degree to which their niches overlap (Pielou, 1972). To explore ecological processes, such as competition over shared resources, both niche breadth and niche overlap provide indirect ways (MacNally, 1983). Moreover, the environmental impacts on the plant community also reflects the adaptation and evolution of the plant community to its conditions. Plant communities that inhabit aquatic ecosystems usually have a complex structure driven by a large number of variables that influence plant-plant interactions (Winemiller & Pianka, 1990). So, it is necessary to evaluate the available resources and the relative amounts of inter- and intra-specific competition by niche width and overlap among the coexisting species of the community in specific environments such as in a novel hydro-fluctuation zone. As the largest hydropower project in the world, the Three Gorges Dam (TGD) on the Yangtze River was initiated in 1994 (Zhang et al., 2013), and first impoundment occurred in June 2003 (Yang et al., 2012). The water level of the reservoir fluctuates from 145 m in summer (May to September) to 175 m in winter (October to April), resulting in the formation of a water level fluctuation zone (WLFZ) with an area of 350 km 2 in the reservoir (Ye et al., 2013). The hydrological regime of the Three Gorges Reservoir (TGR) was the exact opposite of the natural flood rhythms of the Yangtze River (Fan et al., 2012), which formed a unique riparian ecosystem. Before the impoundment of the TGR, the main vegetation types of riparian forests in the zone below an elevation of 175 m were trees (e.g., Pinus massoniana and Cupressus funebris ), shrubs (e.g., Vitex negundo , Securinega suffruticosa and Myricaria laxiflora ) and herbs ( Imperata cylindrica , Arthraxon hispidus and Cynodon dactylon ) (Chen et al., 2008). After the filling of the TGR, the reversal of submergence time and prolonged inundation duration precipitated the loss of previous vegetation, and annual plants such as Setaria viridis , Digitaria ciliaris , and Comnyza canadensis currently became dominant species (Lu et al., 2010; Ye et al., 2013). According to the plant species distribution survey from the WLFZ in the TGR in 2009, the decreased ratio of plant families, genera, and species of post-dam riparian vegetation in 2009 was 26.51%, 29.58% and 42.96%, respectively, compared with the pre-dam riparian plant species in 2001 (Liu et al., 2011). The vegetation investigation of the Pengxi River, Baijia Stream and Xiangxi River in the TGR also showed that the vegetation in the WLFZ of the TGR was seriously degenerated, the community structure was single and the species richness and diversity decreased (Liu et al., 2011; Yuan et al., 2014; You et al., 2017; Xiang, et al., 2020; Li, et al., 2022). The hydrological alterations greatly degraded biodiversity in the TGR disturbance zone, particularly the disappearance of indigenous vegetation significantly would undermine the function of the regional ecosystem service (Zhu et al., 2020). Vegetation restoration in the WLFZ has become an increasing concern in recent years (Ye et al., 2013; Gong et al., 2023; Zhang et al., 2016). Thus, it is important to understand the plant community characteristics in the novel riparian forest. However, there was a lack of application of niche theory to explore its formation mechanism of plant community, which is always a key issue for plant community ecologist. As described above, there have been some reports on plant community characteristics of the WLFZ at the beginning of the impoundment period of the TGR (Su et al., 2020; Zhang et al., 2013; Ye et al., 2013). However, little is known on how anti-seasonal and continuous flooding hydrological alterations affect the riparian guilds, from functional and niche perspectives, of the unique drawdown zone vegetation after 19 times of operation of the TGR. The TGR catchment provides a unique scenario to investigate the functional response of riparian herbaceous species to the novel anti-seasonal and continuous flooding environments across a 600 km stream gradient in a globally-significant river system. We randomly selected 30 reaches along the shorelines of the TGR subjected to anti-seasonal and continuous flooding. Fieldwork was conducted after 19 times of operation of the TGR in order to answer the following questions. ( 1 ) What were specific plant community characteristics and functional diversity in the unique riparian ecosystem after 19 times of operation of the TGR? ( 2 ) Which plant guilds were favoured or disfavoured by the novel anti-seasonal and continuous flooding environment? and ( 3 ) how did the niche characteristics of dominant species change in various flooding environments, especially along an elevation gradient in the TGR? Accordingly, we hypothesized that ( 1 ) anti-seasonal flooding substantially altered the plant community characteristics and species diversity patterns, and reduced species diversity in the the novel riparian ecosystem of the TGR, ( 2 ) the more niche breadth of dominant plant species in the unique riparian ecosystem would imply that they would utilize more limited resources and the more niche overlap would show the more inter-specific competition and co-existence in the plant community and ( 3 ) anti-seasonal and continuous flooding would precipitate the gradual disappearance of the original diverse niches, resulting in more uniform habitats, and there was obvious competition among species with similar resource requirements. This work will help to provide optimal plant guild selection and scientific plant configuration for ecological restoration efforts in the novel riparian forest of the TGR region and the similar ecologically fragile areas. 2. Materials and Methods 2.1 Study area The TGR region (29°16′ to 31°25′N, 106° to 111°50′E) lies in a 600-km valley from Yichang to upstream Chongqing, China (Fig. 1 ). This area is characterized by a subtropical monsoon climate, with an annual mean temperature of 16.5–19.0℃ and annual mean precipitation ranging from 886 to 1614 mm, 80% of which occurs between April and October (Ye et al., 2011). The soil is purple soil consisting of 29% sand, 49% silt and 22% clay in the top 20 cm. Our study area is located in the water level fluctuation zone of the TGR, where the water level fluctuates from 145 m a.s.l. in summer to 175 m a.s.l. in winter (Ye et al., 2015). Summer is the raining season in the study area which results in seasonal water level fluctuations that temporally range between 145 m and 155 m with flooding periods lasting from a few days to approximately two weeks (Wang et al., 2014). However, due to the regulation of the TGR, the highest water level rise occurs in winter and falls to the lowest level in summer in an annual cycle. These changes in water level fluctuation are opposite to natural seasonal fluctuations and are called “anti-seasonal” (Willison et al., 2013). The duration of anti-seasonal flooding differs according to elevation (i.e., 145—155 m a.s.l. with an average inundation duration of 286 days per year; 155—165 m a.s.l., with an average inundation duration of 237 days per year; and 165—175 m a.s.l., with an average inundation of 169 days per year). 2.2 Vegetation investigation Investigation was conducted in August to September, just before the rise in the wate rlevel in the TGR. At this time of the year, the vegetation in the water level fluctuation zones (WLFZs) was exposed and maximally recovered from the preceding flood, which occurred in the summer, autumn, and winter in the WLFZs. Sample transects with 50 m lengths were defined and were parallel to the water level gradient. Within the transects, 30 reaches were randomly selected along the shorelines of the TGR subjected to anti-seasonal and continuous flooding from upstream to downstream in the Reservoir in 2022 . Among them, 24 sampling sites were located in the tributaries of the Yangtze River (1–3; 10–30) and 6 sampling sites were located in the mainstream ( 4 – 9 ). At each sampling site we established a transect along an elevational gradient, from 145 m a.s.l to 175 m a.s.l. (i.e., bottom, 145–155 m; middle, 155–165 m; and top, 165–175 m). Because flooding regime varies based on elevation, these transects allowed us to investigate the effects of flooding on riparian ecosystem properties. Five 1×1 m herb quadrats were investigated in the three sections of each sampling site, the relative density, relative frequency, relative height and relative coverage. However, survey was only carried out between the elevations of 156–165 m; 166–175 m in Wujiang River and Zhongxian because of high water level during the sampling period. Therefore, a total of 368 plant quadrats were investigated. Each vegetation sample quadrat was a focal point for flora survey and the categorical traits were obtained and the plant species were identified from the Flora Reipublicae Popularis Sinicae ( http.//www.iplant.cn/frps ) and field observations. For each species in a quadrat, we recored all the individuals of a given species in each quadrat, measured the average height of 10 randomly selected individuals and measured the coverage by estimating the projective canopy area. The soil samples (0–20 cm) was investigated using the cutting ring method. Three random topsoil samples (0–20 cm) were collected and then mixed to form a composite sample at each elevation zone of each transect. A total of 129 mixed soil samples were sealed in plastic bags and brought to the laboratory. Soil samples were air-dried and sieved (< 2 mm) before analysis. The sketch map of study area and sampling sections were shown in Fig. 1 . 2.3 Environmental variable analysis Soil pH was determined in a 1.5 soil. solution ratio, using a combination glass electrode (Kabala & Musztyfaga, 2015). Soil organic matter (OM) was determined by potassium dichromate titrimetric solution with the method detection limit (MDL) of 0.5 g kg − 1 TN was determined by the Kjeldahl method. TP and AP were measured by molybdenum-antimony anti-spectrophotometric method. TK and AK were determined by flame photometric method (Bao. 2000). A 15-g sample of soil was extracted by shaking with 100 ml of 2 M KCl for 1 h. Exchangeable NH 4 + -N and NO 3 - -N were determined with spectrophotometer using the Indophenol blue colorimetric method and Phenol disulfonic acid colorimetry, respectively (Ye et al., 2015). The heterogeneity of soil environmental factors in different elevations in the TGR are shown in Fig. 2 . 2.4 Data analysis 2.4.1 Importance value The importance values of different species at a given community were calculated on the basis of the relative coverage (RC), relative frequency (RF), relative height (RH) and the relative density (RD) of each species in different quadrats and then used as the indicators to determine the dominant herbaceous plant species in the WLFZs and the ecological niche measurement. The calculation formula is. P i =(RC + RH + RF + RD)/4 ( 1 ) Where P i is the importance value of the i -th species, RC is the projective coverage of a given species divided by the total coverage of all the species in all the quadrats; RF is number of occurrence of the species divided by the total number of occurrence of all the species in all the quadrats, RH is average height of the species divided by the total height of all the species in all the quadrats and RD is the total number of individuals of the species in all quadrats divided by the total number of all the species in all the quadrats. 2.4.2 Species diversity index Fisher's α-diversity index was characterized by species number ( S ), Shannon diversity index ( H ), Pielou evenness index ( E ), and Simpson dominance index ( D ). The calculation formulas are (Curtis & McIntosh, 1951). Shannon diversity index: \(H=-\varSigma {P}_{i}ln{P}_{i}\) ( 2 ) Pielou evenness index: \(E=\frac{H}{ln\text{S}}\) ( 3 ) Simpson dominance index: \(H=-\varSigma {P}_{i}^{2}\) ( 4 ) Where P i is the importance value of the i -th species, S is the number of species appearing within the quadrat and N is the total number of species present within the quadrats. 2.4.3 Niche breadth The niche breadth, as proposed by Levin, was calculated by Colwell's modified formula (Feinsinger et al., 1981) : $${B}_{i}=\frac{1}{r\times \sum _{\text{h}=1}^{\text{r}}{(P}_{ih}{)}^{2}}$$ 5 Where B i is the niche breadth of the i -th species, P ih is the ratio of the importance value of the i -th species at the h -th resource level to the sum of the importance values of the species at all resource levels, r is the number of resource levels, and the value range is [0,1]. 2.4.4. Niche overlap The Pianka formula was used to calculate niche overlap (Pianka, 1974). $${O}_{ih}=\frac{\underset{h=1}{\overset{r}{\int }}{P}_{ih}{P}_{jh}}{\sqrt{\underset{h=1}{\overset{r}{\int }}{P}_{ih}^{2}\underset{h=1}{\overset{r}{\int }}{P}_{jh}^{2}}}$$ 6 Where O ij is the niche overlap of populations i and j , and p ih and p ij are the proportion of the importance values of the i -th and the j -th species at the h -th resource level in the synthesis of the importance values of the species at all resource levels, and r is the number of resource levels, and the range of the formula is [0, 1]. 2.4.5. The total mean of niche overlap values The total mean value of niche overlap value among all populations ( TAO ih ) in the sample land is calculated as follows (Chen et al., 2019). $${TAO}_{ih}=\frac{{TO}_{ih}}{TP}$$ 7 Where, TO ih is the total number of niche overlap values among all populations in the sample plot, and TP is the total species logarithm. 2.4.6. Statistical analysis Two-way clustering analysis provides a very visual picture of the distribution, classification, and degree of similarity between species in a community. In this study, we conducted clustering analysis of plant species in the surveyed quadrat, and calculated the significant values of the species in the sample to obtain the plant significant value matrix as the basis of clustering analysis according to the program method in "Quantitative Ecology-Application of the R Language". The groups were designated as riparian guilds where each vegetation group comprising a guild. ( 1 ) contains species sharing similar features; and ( 2 ) shares a similar environment. Canonical correspondence analysis (CCA) was used to analyze the data of 10 environmental factors from 10 sample sites in the TGR area and 31 plant species after excluding species with frequency less than 3 from the sample sites to get information such as the structure of the biological community, the relationship between the biological community and environmental factors. All the analyses were performed using SPSS 22.0 and Origin 2018 for Windows except the CCA which was performed using Canoco 5.0 and two-way clustering analysis used the program packages such as vegan, gclus and cluster in R software based on investigation in 2022. 3. Results 3.1 Foristic composition A total of 73 vascular plant species were identified, belonging to 65 genera of 25 families, including 52 species of annual herbs, 20 species of perennial herbs and 1 species of shrub, accordingly accounting for 71.23%, 27.39% and 1.37% of the total number of species, respectively. The plant families with the largest number of species in the studied area were Compositae (N = 15, 20.56%), Gramineae ( N = 12, 16.45%), Leguminosae ( N = 9, 12.32%), Euphorbiaceae ( N = 5, 8.22%), respectively. A significant proportion of plants of single genus and species in the survey area were in 13 families (i.e., 13 genera and 13 species), representing 52% of the total number of families, 20% of the total number of genus and 17.8% of the total number of species, respectively. There were different plant species, genera, and families at different altitudes (145–155, 155–165, and 165–175 m) in the WLFZ of the TGR. Individually, there were 38 vascular plant species belonging to 32 genera of 16 families at the 145–155 m, 43 vascular plant species belonging to 39 genera of 19 families at the 155–165 m and 57 vascular plant species belonging to 50 genera of 18 families at the 165–175 m (Fig. 2 ). Species numbers significantly increased with increasing elevation. Annual herb was the dominant life form in the whole study area, accounting for 78.95% of plant species at the elevation intervals of 144–155 m, 74.42% at the altitudes of 155–165 m and 71.93% at the altitudes of 165–175 m, respectively. The less frequent life form was perennial herb (145–155 m. n = 7, 18.42%; 155–165 m. n = 11, 25.58%; 165–175 m. n = 16, 28.07%). Compositae and Gramineae were the larger families with 6–15 species than other ones and contributed to 37.01% of the total plant species in the current study (Fig. 2 ). The proportion of Compositae and Gramineae plants showed an upward trend with the increasing altitude. The proportion of annual herbs species showed a decreasing trend along altitude gradients, while the proportion of perennial herb species showed an opposite trend. 3.3 Spatial variation in plant diversities The H values ranged from 0.831 to 1.661 in the WLFZ, increasing with the increasing altitude, of which the highest H (1.458 ± 0.035) appeared at the altitude of 165–175 m. The S and D also showed a rising trend in spatial variation with altitude in the WLFZ, but the latter is not significant. However, the E showed a contrary trend that E decreased with the increasing altitude ( p < 0.01, Fig. 3 ). The H , D , S and E showed same trends in the spatial distribution patterns from upstream to downstream in the WLFZ of TGR, which firstly showed a significant increasing trend ( p < 0.05), reached the highest in the middle reaches in the Tangxi River, and then decreased in the downstream reaches (Wujiang River to Tongzhuang River) (Fig. 4 ). And the H , E and S reached the highest point at Tangxi River. In short, the spatial heterogeneity of the H , D , and E for plants from upstream to downstream were strong in the TGR of the Yangtze River, and less for S . 3.4 Classification of guilds In this study, the important values of species in the plant community were selected as the clustering basis. Four different clustering methods were used to cluster 368 quadrats (communities) in the WLFZ (Fig. 5 ). In order to interpret and compare the results of the four clustering analysis methods, we need to find the interpretable clusters. As the value of the difference between the two branches in the cluster tree, the fusion level value of the cluster tree can help to judge the clustering level of different clustering methods through analysis. The results of fusion level and clustering tree showed that the single link clustering was the most reasonable among the four clustering methods (Fig. 5 ). Then, the single chain clustering method was selected to cluster 368 samples in the WLFZ of the TGR. By calculating the correlation between the original distance and the binary matrix representing different classification levels, the classification level corresponding to the highest correlation coefficient was selected as the optimal grouping scheme, and the results showed that it was the most reasonable to be divided into 12 guilds (Fig. 6 ). Each guild represented a plant community type, and it was named after the dominant species in the community. The naming format refers to the description of plant community naming in《Chinese Vegetation》(Wu, 1980). The 12 main plant guilds were discovered as followed. Guild 1. Ass. Eclipta prostrata + Cynodon dactylon , hygrophyte and mesophyte community, flood-tolerant riparian herbs, including 5 samples and 16 species. The main companion species were Digitaria sanguinalis , Euphorbia humifusa , and Acalypha australis , with a distribution range of 155–175 m in elevation. Guild 2. Ass. Bidens pilosa, hygrophyte and mesophyte community , competitive annual herbs, including 6 samples and 21 species. The companion species are Polygonum hydropiper, Amaranthus retroflexus, Echinochloa crusgalli, and Xanthium sibiricum, which were mainly found at elevations of 165–175 m. Guild 3. Ass. Bidens tripartita, hygrophyte and mesophyte community , competitive annual herbs,including 3 samples and 13 species. The companion species are Xanthium sibiricum, Digitaria sanguinalis, Echinochloa crusgalli, Bidens pilosa, Cynodon dactylon, the main distribution altitude is 165–175 m. Guild 4. Ass. Digitaria sanguinalis , hygrophyte and mesophyte community , competitive annual herbs, including 9 samples and 18 species. The companion species are Setaria viridis , Acalypha australis , and Xanthium sibiricum , which were mainly distributed at an elevation of 165–175 m. Guild 5. Ass. Echinochloa crusgalli + Digitaria sanguinalis + Setaria viridis, mesophyte community , competitive riparian herbs, including 5 samples and 18 species. The companion species were Bidens pilosa, Xanthium sibiricum and Humulus scandens, which are mainly found at elevations of 145–175 m. Guild 6: Ass. Humulus scandens , hygrophyte and mesophyte community , competitive riparian herbs, including 2 samples and 8 species. The companion species are Bidens pilosa, Echinochloa crusgalli , Eleusine indica and Chenopodium ambrosioides which were mainly found at elevations of 165–175 m. Guild 7. Ass. Setaria viridis, hygrophyte and mesophyte community , competitive riparian herbs, including 19 samples and 28 species. The companion species are Digitaria sanguinalis, Xanthium sibiricum, Bidens pilosa, and Cynodon dactylon and Eriochloa villosa, which were mainly found at elevations of 165–175 m. Guild 8: Ass. Cynodon dactylon + Abutilon theophrasti + Salvia plebeia , hygrophyte and mesophyte community, stress-tolerant woody and herb species, including 6 samples and 15 species. The companion species are Solanum nigrum, Digitaria sanguinalis, Bidens pilosa and Setaria viridis , which were mainly found at elevations of 165–175 m. Guild 9. Ass. Cynodon dactylon , hygrophyte and mesophyte community, flood-tolerant riparian herbs, including 293 samples and 62 species. The companion species are Xanthium sibiricum, Echinochloa crusgalli, Cyperus rotundus , and Bidens pilosa , which were mainly found at elevations of 145–175 m. Guild 10. Ass. Conyza canadensis + Bidens pilosa, hygrophyte and mesophyte community , competitive annual herbs, including 11 samples and 20 species. The companion species are Artemisia argyi, Setaria viridis, Echinochloa crusgalli and Eriochloa villosa, which were mainly found at elevations of 165–175 m. Guild 11. Ass. Cynodon dactylon + Melilotus officinalis, hygrophyte and mesophyte community , stress-tolerant herb and woody species, including 6 samples and 15 species. The companion species were Setaria viridis, Anemarrhena asphodeloides, Echinochloa crusgalli, Bidens pilosa and Abutilon theophrasti, which are mainly found at elevations of 155–175 m. Guild 12. Ass. Cynodon dactylon + Echinochloa crusgalli + Cyperus rotundus, hygrophyte and mesophyte community , flood-tolerant riparian herbs including 3 samples and 9 species. The companion species are Amaranthus retroflexus, Xanthium sibiricum and Torulinium ferax, which are mainly found at elevations of 145–155 m. 3.5 Response of plant communities in the TGR to water level changes and environmental factors All soil chemistry properties were significant ( p < 0.05) across sites (Fig. 7 ). SM, OM, TN, TP, pH firstly decreased and then gradually increased with "V" type changes along the altitude gradient, of which the lowest in the TGR area at 155–165 m altitude, and all changes were significant except for pH. The AP, NH 4 + , NO 3 - in the TGR area had a significant decreasing trend with the increasing altitude. Low altitude. 145–155 m; Middle altitude. 155–165 m; High altitude. 165–175 m. Values are means ± SE. SM, soil moisture; OM, organic matte; TN, total nitrogen; NO 3 - , nitrate; NH 4 + , ammonium; TP, total phosphorus; AP, available phosphorus. Soil environmental factors and hydrological factor in the WLFZ significantly influenced the distribution pattern of plant guilds (Fig. 8 ). The ranking of plant guilds in response to water level changes and environmental factors in the WLFZ of the TGR was shown in Table 1 , and the first four paradigmatic axes cumulatively explained 44.3% of the guild changes. The species-environment correlation coefficients for axes 1 and 2 were 0.8615 and 0.8777, respectively, and the sum of the eigenvalues of the first two axes accounted for 62.83% of the total eigenvalues, containing most of the ranking information, so the data from the first two axes were used to analyze the relationship between guilds and environmental factors. As can be seen from Tables 1 and 2 and Fig. 8 , the highest correlation between flooding time and elevation with axis 1 was − 0.8297 and 0.7943, respectively. The correlation between OM and TP with axis 2 was higher at 0.5119 and 0.4327, respectively. As seen by the CCA ordination diagram (Fig. 8 .), the position of each guild in the ordination space can reflect the ecological characteristics of the guilds and their distribution patterns. With the increasing altitude, the distribution patterns of the plant guilds in the WLFZ were like this. The lower altitude area (145–155 m) was dominated by annual plant guilds, i.e., Echinochloa crusgalli and Amaranthus retroflexus . The middle part (156–165 m) was dominated by annuals and perennial plant guilds, i.e., Cynodon dactylon, Cyperus rotundus, Bidens pilosa , Xanthium sibiricum and Melilotus officinalis . The top area (166–175 m) was dominated by shrub and herb plant guilds, i.e., Echinochloa crusgalli, Cynodon dactylon, Eriochloa villosa and Abutilon theophrasti . Table 1 CCA ranking axis eigenvalues and interpretation Axis 1 Axis 2 Axis 3 Axis 4 Eigenvalue 0.1168 0.0879 0.0692 0.0519 Explained changes (cumulative) 12.38 21.69 29.02 34.52 Species-environmental correlation 0.8615 0.8777 0.7971 0.8052 Fitting variation in interpretation (cumulative) 27.96 48.99 65.55 77.97 Table 2 Correlation of 10 soil chemistry properties with each CCA axis Axis 1 Axis 2 Axis 3 Axis 4 Elevation 0.7943 0.1183 0.0124 0.0287 Flooding duration -0.8297 0.0702 0.0519 -0.0828 SM -0.0779 0.0455 0.2981 -0.7346 AP -0.4317 0.2144 0.1826 -0.1407 NH 4 + -0.3453 -0.2666 0.1734 -0.0061 NO 3 − -0.2049 0.2193 0.3508 0.0255 OM 0.2296 0.5119 -0.3025 0.0315 pH -0.3274 -0.2285 -0.2558 0.2327 TN 0.2662 -0.0272 0.0923 -0.3163 TP 0.2579 0.4327 0.5212 -0.1251 3.6 Niche breadth The niche breadth of species in the WLFZ were listed in the Table 3 , the top 8 of which were C. dactylon (21.918) > X. sibiricum (13.275) > B. pilosa (11.318) > E. crusgalli (9.472) > C. rotundus (6.407) > Eclipta prostrata (6.052) > D. sanguinalis (5.967) > S. viridis (5.816). And the niche breadth of C. dactylon was significantly larger than that of others. Under different altitude sections, C. dactylon (7.0836) > E. crusgalli (3.3973) > B. pilosa (3.1698) at the lower elevations (145–155 m); C. dactylon (8.176) > X. sibiricum (4.436) > E. crusgalli (3.721) at the middle elevations (155–165 m); C. dactylon (6.659) > X. sibiricum (6.0956) > E. prostrata (4.889) at the highest elevations (165–175 m). The dominant species had the different niche breadth in different elevations. Of these, the niche breadth of C. dactylon at the middle elevations (155–165 m) was the highest (8.176) and lowest at the higher elevations (165–175 m). And the niche breadth of C. dactylon was obvious higher than other species at the lower (145–155 m) and the middle elevations (155–165 m), but not at the highest elevations (165–175 m). The niche breadth of most of perennial herbs were higher at the highest elevations (165–175 m) than that at the lower (145–155 m) and middle elevations (155–165 m). Table 3 Changes of Importance values and niche breadth of dominant plants at different altitudes in the WLFZ Species P i B i 145–155 m 155–165 m 165–175 m Total 145–155 m 155–165 m 165–175 m Total Cynodon dactylon 3.854 4.537 3.470 11.861 7.084 8.176 6.659 21.918 Xanthium sibiricum 1.061 1.215 1.280 3.556 2.743 4.436 6.096 13.275 Cyperus rotundus 1.444 1.085 0.567 3.097 2.505 2.886 1.016 6.407 Echinochloa crusgalli 0.956 1.183 0.787 2.926 3.397 3.721 2.353 9.472 Setaria viridis 0.415 1.157 1.199 2.772 0.766 1.960 3.091 5.816 Bidens pilosa 0.717 0.951 1.003 2.672 3.170 3.259 4.889 11.318 Digitaria sanguinalis 0.433 0.848 1.179 2.460 0.679 2.345 2.943 5.967 Polygonum hydropiper 0.957 0.665 0.747 2.369 1.536 1.811 2.365 5.712 Eclipta prostrata 0.454 0.592 0.809 1.856 1.901 2.188 1.963 6.052 Abutilon theophrasti 0.636 0.604 0.486 1.726 1.447 2.236 1.015 4.698 Alternanthera philoxeroides 0.671 0.300 0.689 1.659 0.154 0.766 1.183 2.103 Bidens tripartita 0.621 0.453 0.581 1.655 0.216 1.314 1.417 2.947 Acalypha australis 0.445 0.494 0.438 1.377 0.893 0.936 1.153 2.981 Solanum nigrum 0.243 0.555 0.473 1.271 0.885 2.271 0.707 3.863 Eriochloa villosa 0.151 0.300 0.773 1.224 0.214 0.253 0.796 1.263 Melilotus officinalis - - 0.937 0.937 - - 1.210 1.210 Eleusine indica 0.249 0.234 0.325 0.808 0.394 0.222 0.479 1.096 Cyperus difformis 0.270 0.176 0.221 0.667 0.353 0.067 0.620 1.039 Humulus scandens 0.129 0.231 0.190 0.550 0.175 0.326 0.425 0.926 Artemisia argyi 0.164 0.162 0.196 0.521 0.077 0.067 0.570 0.713 Ageratum conyzoides 0.033 0.189 0.259 0.482 0.077 0.079 0.369 0.525 Euphorbia humifusa 0.035 0.294 0.151 0.480 0.077 0.348 0.407 0.832 Aeschynomene indica 0.160 0.178 0.134 0.472 0.083 0.382 0.198 0.664 Conyza canadensis - 0.057 0.402 0.459 - 0.123 1.444 1.566 Amaranthus retroflexus 0.133 0.055 0.269 0.457 0.244 0.067 0.715 1.026 Phyllanthus urinaria 0.204 0.165 0.086 0.456 0.463 0.522 0.162 1.148 Ammannia baccifera 0.446 - - 0.446 0.077 - - 0.077 Erigeron annuus 0.038 0.236 0.171 0.445 0.077 0.071 0.138 0.286 Salvia plebeia 0.209 0.050 0.124 0.383 0.161 0.100 0.258 0.519 Portulaca oleracea 0.252 0.073 - 0.325 0.440 0.122 - 0.562 Pouzolzia zeylanica - 0.023 0.275 0.298 - 0.067 0.564 0.631 Artemisia carvifolia - 0.112 0.182 0.295 - 0.148 0.430 0.579 Anemarrhena asphodeloides - 0.067 0.197 0.265 - 0.071 0.452 0.524 Physalis alkekengi 0.042 0.147 0.063 0.252 0.067 0.208 0.125 0.400 Vigna radiata 0.139 - 0.108 0.248 0.083 - 0.125 0.208 Arachis hypogaea - - 0.211 0.211 - - 0.091 0.091 Aster tataricus 0.063 - 0.127 0.190 0.139 - 0.267 0.406 Lindernia procumbens 0.169 - - 0.169 0.056 - - 0.056 Chenopodium ambrosioides 0.116 0.045 - 0.161 0.215 0.071 - 0.286 Mazus japonicus - - 0.161 0.161 - - 0.071 0.071 Ambrosia artemisiifolia - 0.061 0.095 0.156 - 0.204 0.333 0.537 Alopecurus aequalis - - 0.152 0.152 - - 0.090 0.090 Sesbania cannabina - 0.123 - 0.123 - 0.421 - 0.421 Hemistepta lyrata - - 0.107 0.107 - - 0.167 0.167 Vetiveria zizanioides - - 0.107 0.107 - - 0.368 0.368 Lindernia crustacea 0.054 - 0.045 0.099 0.077 - 0.167 0.244 Bupleurum longiradiatum - 0.091 - 0.091 - 0.067 - 0.067 Dactyloctenium aegyptium - 0.087 - 0.087 - 0.271 - 0.271 Juncus effusus - 0.083 - 0.083 - 0.091 - 0.091 Phyla nodiflora - 0.082 - 0.082 - 0.091 - 0.091 Celosia argentea - - 0.080 0.080 - - 0.196 0.196 Sorghum bicolor - - 0.072 0.072 - - 0.139 0.139 Daucus carota - - 0.072 0.072 - - 0.416 0.416 Leptochloa chinensis - - 0.071 0.071 - - 0.318 0.318 Pilea cavaleriei - - 0.067 0.067 - - 0.071 0.071 Cosmos bipinnata - 0.063 - 0.063 - 0.056 - 0.056 Mosla scabra - - 0.058 0.058 - - 0.167 0.167 Torulinium ferax 0.057 - - 0.057 0.077 - - 0.077 Artemisia capillaris - - 0.056 0.056 - - 0.067 0.067 Sida acuta 0.050 - - 0.050 0.083 - - 0.083 Euphorbia hypericifolia - - 0.049 0.049 - - 0.103 0.103 Arthraxon hispidus - - 0.042 0.042 - - 0.125 0.125 Trigonotis peduncularis - - 0.036 0.036 - - 0.071 0.071 Mimosa pudica - - 0.035 0.035 - - 0.071 0.071 Rorippa indica 0.033 - - 0.033 0.077 - - 0.077 Leucaena leucocephala 0.029 - - 0.029 0.077 - - 0.077 Commelina communis - - 0.028 0.028 - - 0.067 0.067 Vicia sepium - - 0.025 0.025 - - 0.071 0.071 Medicago sativa - - 0.023 0.023 - - 0.071 0.071 Corydalis pallida - 0.017 - 0.017 - 0.077 - 0.077 Euphorbia helioscopia - 0.014 - 0.014 - 0.067 - 0.067 Cucumis sativus - - 0.011 0.011 - - 0.056 0.056 Erigeron acer - - 0.007 0.007 - - 0.056 0.056 “-”. Species was disappeared; P i . Importance value; B i . Niche breadth. It could be seen from the correlation between niche breadths and important values of each elevation in the surveyed sample plot under three types of elevations were positively correlated (Fig. 9 ). There was also a significant positive correlation between the niche breadths and the important values of each species, and the explanatory variables were high. The dominant species with high important value always had the higher niche breadths value. C. dactylon both had the highest niche breadths and important values. 3.7 Niche overlap Niche overlap by species for each altitude section was calculated (Fig. 10 .). There were 703 niche overlap indexes calculated by 38 species at the altitude of 145–155 m, 33.85% of which were 0, 35.85% of which were greater than 0.5 and 38.55% of which were less than 0.2. C. dactylon , X. sibiricum , S. viridis , and D. sanguinalis all had the high niche overlap value compared with most of species. However, there were also some species with low niche breadths and important value, such as H. scandens , L. crustacea and C. ambrosioides , which had high niche overlap values. There were 901 niches overlap indexes calculated by 43 species at the altitude of 155–165 m, 44.73% of which were 0, 18.09% of which were greater than 0.5 and 49.28% of which were less than 0.2. C. dactylon , X. sibiricum , S. viridis , and D. sanguinalis all had the high niche overlap value with most of species. There were 1596 niches overlap indexes calculated by 57 species at the altitude of 165–175 m, 42.42% of which were 0, 20.86% of which were greater than 0.5 and 48.81% of which were less than 0.2. C. dactylon , C. rotundus , X. sibiricum , P. hydropiper , and E. crusgalli all had the high niche overlap value with most of species. Niche overlap index of the same species in different altitudes was different. The niche overlap values of C. dactylon were higher at the middle elevations (155–165 m) than that at the higher (165–175 m) and lower elevations (145–155 m). 4. Discussion 4.1. Anti-seasonal flooding substantially reduced species diversity in the WLFZ of the TGR A unique riparian ecosystem has been created as a result of anti-seasonal and continuous flooding after TGR operations, which notably influences the species diversity distribution patterns of plant communities and their functional characteristics (Li et al., 2022). Before the impoundment of the TGR, there were 405 vascular plants in the riparian area of the TGR (Wang et al., 2002). However, in the early stage of the TGR impoundment in 2009, only a total of 231 species, belonging to 61 families and 169 genera, was found in the WLFZ of the TGR (Liu et al., 2011). After the early 7 years of the TGR impoundment in 2010, Zhang et al., (2013) found that a few shrubs ( Boehmeria nivea, Lespedeza davidii, Lespedeza cuneata ) and trees ( Morus alba, Albizia kalkora and Broussonetia papyrifera ) only appeared at the altitude of 170 m. The main vegetation type was herbs in the WLFZ. In the present study, after the early 19 years of the TGR impoundment, a total of 73 vascular plant species were identified in the WLFZ. Annual herbs accounted for the highest percentage of all life forms at each altitude. Annuals, perennials and shrubs accounted for 71.23%, 27.39% and 1.37% of the total number of species, respectively. Thus it could be seen, anti-seational and continuous flooding triggered the dramatic alterations in floristic composition, structure, and distribution pattern of plant communities in the riparian zone. At the same time, after 19 years of water storage, plant life forms have been altered dramatically in the new riparian forest. This novel anti-seasonal flooding reduced functional diversity, mostly owing to the loss of stress-tolerant woody species and competitive perennial herbs. Essentially new hydromorphological conditions following damming limited recruitment of native shrub and tree species guilds sensitive to floods (to drag forces, inundation, and anoxia). Thus it can be seen that woody plants (trees and shrubs) showed the greatest decrease, and the proportion of perennial herbs also decreased, while the proportion of annual herbs increased significantly, indicating that herbs, especially annual herbs, i.e. Compositae, Gramineae and Leguminosae families, are more suitable for the environment of water level fluctuations in the TGR. Thus it could be seen, the pre-dam vegetation failed to persist under the new riparian ecosystem, and the species richness and diversity of the riparian forests were significantly lower due to the great hydrological shifts by the TGD construction (New & Xie, 2008; Chen et al., 2012; Chen et al., 2022). A plausible reason was that most annuals, i.e., Compositae, Gramineae and Leguminosae, germinate in spring and fructify in autumn during the low water level of the TGR operation within a growth season, and have the flooding tolerance and the capacity to synchronize germination and growth within a short-exposure period, which underlie the plant species alterations. Therefore, these adaptive annuals survive as dominant species in the WLFZ of the TGR mainly because their phenology do not compound with the submergence occurring time. The recession of the water level left a nearly barren drawdown zone and provided an entire growing season for the forbs and graminoids, especially for the annual and biennial and perennial species. With its short life cycle, annual herbs were able to go from seed to seed life cycle in a relatively short period of time after water receding and before water storage. The next year, a new life cycle began with the emergence of seeds from nearby seed sources or soil seed banks (De Souza et al., 2021). After receding, clonal growth can quickly expand space and gain an advantage in the inter-specific competition by their extensive lateral spread and forming dense, nearly monospecific stands, i.e., C. dactylon , which can quickly re-sprout following continuous inundation and take advantage of the short-exposure period before the reservoir is filled again. Thus, the proportion of annual herbaceous species showed a decreasing trend while the proportion of perennial herbaceous species showed an increasing trend along elevation gradients. The transformed species richness of forbs, graminoids, annuals, biennials and perennials increased significantly, especially the Compositae, Graminaceae and Leguminaceae plants. Species diversity distribution along elevation gradients has different patterns. Some studies have demonstrated that species richness patterns from the lowest to highest elevations may show a monotonic decrease, or a monotonic increase; others have revealed hump-shaped patterns with a peak in richness at mid-elevations (Mallen-cooper & Pickering, 2008; Trigas et al., 2013; Arturo & Lauro, 2005). In the present study, the S, H and D increased with the increasing elevation but E showed a contrary trend (Fig. 3 ). This species distribution pattern might be caused by several synergetic attributes (e.g., the submergence depth, the tolerant capacity to flooding, the life form, the dispersal mode, and the inter-specific competition) (Zhang et al., 2013). The lower elevation area (145–155 m) is generally prone to more severe flooding with a greatest depth of inundation (30 m) and prolonged inundation duration (nearly half 6 months), which resulted in the lower S, and H than the higher elevation area (156–165 m and 165–175 m). Thus, these annual species in the low elevation area may rapidly attain maturity before being submerged with short life cycle (Zhang et al., 2013). At the highest elevations (166–175 m), seed dispersal by wind, water, animals, and humans might be important factors resulting in the higher diversity index (Merritt & Wohl, 2006). However, H showed hump-shaped patterns with a peak at mid-reaches from upstream to downstream (Fig. 4 ). The middle reaches of the reservoir area were mostly forested on both sides of the Yangtze River, with less agricultural cultivation and less human influence. In the downstream reaches, the Citrus farming industry on both sides of the Xiangxi and Tongzhuang rivers was booming, and the plant communities on both sides of the river was more affected by agricultural farming and human interference. Ecological characteristics of plant guilds as an assemblage of plant population are response to the environment changes and are more pronounced during succession (Yang et al., 2012; Ge et al., 2020). In this study, it was found that the main influence factors affecting the spatial distribution of the plant guilds in the new riparian forest were hydrological factors, such as elevation (different flooding depths) and flooding time. So, the pattern of the plant guilds in the TGR was mainly affected by water level disturbance. This result was largely consistent with other results that hydrological conditions determined the vegetation diversity and aboveground biomass patterns at the elevation gradients of the drawdown zone (Wang et al., 2014). It can be seen that the vegetation spatial distribution of the TGR area was heavily influenced by the hydrological factors, i.e., different flooding depth and flooding time in the reservoir area and the species diversity was significantly reduced. Soil nutrient concentrations could also strongly affect plant species diversity and evenness (Aerts, et al., 2003). In the present study, the concentrations of TN and TP appeared to be higher at the elevations of 165–175 m than at the elevations of 145–155 m and 155–165 m. The continuous submergence in winter and the high frequency of floods in summer may result in this pattern for soil nutrients may be released when submerged and soil that serves as a nutrient source may be scoured by repeated flooding. Qui & McComb (1996) also reported that the concentration of TN was reduced after continuous submergence. And Roem & Berendse (2000) studied nutrient supply ratio as possible factors determining changes in plant species diversity in grassland and heathland communities, which showed that plant species with high diversity were at balanced N/P ratios between 10 and 14. However, in the present study, N/P ratios of the soil was between 0.98 and 1.56 with an average of 1.26, which showed that N was a limiting factor in the soil in the new riparian forest. The increase of N supply in a N-limited grassland (e.g., N/P ratio < 10) may lead to an increase in biodiversity (Roem & Berendse, 2000). In this study, the distribution patterns of plant guilds were positively associated with TN, TP, and OM, while negatively correlated with pH, NH 4 + -N, NO 3 − -N, and AP in the CCA (Fig. 8 b.). Of these, the significantly negative correlation between NO 3 − -N and the distribution patterns of plant species ( p < 0.05) was consistent with the results that excess of NO 3 − -N is known for its negative effect on the diversity of plant guilds (Aerts, et al., 2003). Therefore, N might be a soil nutrient limiting factor in determining the alterations in plant species diversity and plant distribution patterns in addition to elevation gradients and flooding time in the new riparian forest of the TGR. The results also corroborated the trend of the species diversity index increasing with the elevation gradients. At higher elevations, the number of plant species is increasing and the competition between species becoming more intense. From bottom to top along axis 2, OM and TP rose (Fig. 8 b.). This result was basically the same as the pattern shown in Table 2 , which showed that the influence of elevation and flooding on the distribution pattern of the plant guilds in the TGR was more obvious than that of OM and TP, and the first order axis could explain the interrelationship between the plant guild and the habitat in the declining zone (Fig. 8 c.). That is, although the spatial distribution of the plant guilds in the subduction zone of the TGR area was the result of a combination of multiple factors, the influence of elevation gradients and flooding time played a dominant role in the formation of the spatial pattern of the plant guilds in the new riparian forest of the TGR and the second factors were TN, TP, and OM. In the TGR area, the plant guilds were distributed from left to right along the elevation and flooding time, as follows Ass. C. dactylon + E. crusgalli + C. rotundus ; Ass. C. dactylon + A. theophrasti + S. plebeia ; Ass. E. crusgalli + D. sanguinalis + S. viridis ; Ass. C. dactylon ; Ass. B. pilosa ; Ass. B. tripartita ; Ass. D. sanguinalis ; Ass. H. scandens ; Ass. S. viridis ; Ass. C. canadensis + B. pilosa ; Ass. E. prostrata + C. dactylon ; Ass. C. dactylon + M. officinalis (Fig. 8 a.). There were some overlaps between the types. Ass. C. dactylon + E. crusgalli + C. rotundus and Ass. C. dactylon + A. theophrasti + S. plebeia located at the altitude gradient of 145–155 m, with long flooding durations and short growth durations. The medium elevation gradient (155–165 m) was for the Ass. E. crusgalli + D. sanguinalis + S. viridis and Ass. C. dactylon . Ass. B. pilosa , Ass. B. tripartita , Ass. D. sanguinalis , Ass. H. scandens , Ass. S. viridis , Ass. C. canadensis + B. pilosa , Ass. E. prostrata + C. dactylon and Ass. C. dactylon + M. officinalis were distributed at high altitudes (165–175 m) in the WLFZs, with less or almost unaffected by flooding. In the early stages of flooding in 2010, there were 18 main plant guilds in the WLFZ of the TGR, including 5 xerophyte, 6 hygrophyte and 7 mesophyte guilds (Chen et al., 2012). In the present study, after 19 times of water level fluctuations in the TGR, the 12 main plant guild types were discovered, belonging to hygrophyte and mesophyte communities. Xerophyte guilds almost disappeared. Thus, the taxonomic and functional characteristics of communities were differently as they may respond to important drivers differently. The vegetation composition of the WLFZs in the TGR showed a s ignificant change with a transition from xerophytes to hygrophytes and mesophytes with the increasing flooding time. The observed riparian plant guild response patterns to prolonged submergence in the WLFZs of Yangtze River might hopefully be transferred to similiar rivers with little or no existing information in other regions regardless of whether or not they share species. The guild approach helps develop general frameworks to predict vegetation responses to changing environmental conditions. 4.2. Niche structure and utilization of limited resources Niche breadth describes a suite of environments or resources, in the broadest sense, which a species can inhabit or use, which measures the range of resource characteristics across which a species exists, and indicates the extent that a species utilizes different types of resources (Slatyer et al., 2013), while niche overlap refers to the partial or complete sharing of resources or other ecological factors (predators, foraging space, soil type, and so on) by two or more species (Colwell & Futuyma, 1971). The measures of niche breadth and overlap are all based on the distribution of individual organisms, by species, within a set of resource states (Colwell & Futuyma, 1971). In the present study, the dominant species were C. dactylon , X. sibiricum , C. rotundus , E. crusgalli , S. viridis , B. pilosa , D. sanguinalis and P. hydropiper in the riparian forest of the TGR according to the importance value and niche breadth. The correlations between niche breadths and important values of each elevation were positively correlated in the surveyed sample plots under three types of elevations (Fig. 3 .). Under different altitude sections according to niche breadth, C. dactylon (7.0836) > E. crusgalli (3.3973) > B. pilosa (3.1698) at the lower elevations (145–155 m); C. dactylon (8.176) > X. sibiricum (4.436) > E. crusgalli (3.721) at the middle elevations (155–165 m); C. dactylon (6.659) > X. sibiricum (6.0956) > E. prostrata (4.889) at the highest elevations (165–175 m). C. dactylon was the most dominant species in the novel riparian forest with highest importance value and niche breadth at each altitude. C. dactylon might have evolved morphological, physiological, and biochemical adaptations to oxygen deficiency, such as dormant tubers or rhizomes (Zhang et al., 2013). So, it could germinate quickly after submerged period to against the coming dry period to achieve the greatest competitive advantages in the WLFZ. There were the most of species pairs with the niche overlap index less than 0.2 or 0 at the middle altitude (155–165 m). The vegetation in the middle altitude (155–165 m) were the least affected by the Yangtze River flooding during the dry period. C. dactylon almost formed a single-species community at the middle altitude (155–165 m), because of its strong acclimation and fast growth as well as facile vegetative propagation compared with other species. Niche breadth in the study area had high niche overlap between species, but in some habitat conditions, the species with narrower niche breadth appeared larger niche overlap. There were some plants, such as H. scandens , L. crustacea and C. ambrosioides , niche overlap value was 1.00, almost perfect overlap. Most of these species had lower niche overlap with those dominant species. In fact, the niche occupation of resource space between two species was only infinitely close, so the overlap was only infinitely close to 1.00. This indicated that there was no direct linear relationship between niche breadth and niche overlap, which was caused by the heterogeneity of spatial distribution of environmental resources available to species (Chen et al., 2019). The TAO ih in the different altitude area was highest at the altitude of 145–155 m (0.3642), lower at 165–175 m (0. 2619) and 155–165 m (0.2524) in descending order. The vegetation in the lower elevations (145–155 m) suffered the longest periods of winter flooding and summer flood. So they had the shortest time to complete their life cycle under the influence of both winter storage and summer flood. The results showed that anti-seasonal and continuous flooding would lead to the gradual disappearance of the original diverse niches, resulting in more uniform habitats, and more obvious competition among species with similar resource requirements. The comprehensive ecological level analysis concluded that, after 19-year inundation of the TGR, the vegetation of the new riparian forest was still in the high niche overlap, intense competition, and species specialization, which showed that the vegetation was still in the early stage of primary succession, ecosystem stability was poor, and habitat fragmentation was severe in the TGR area. 4.3. Practical implications for vegetation restoration and reconstruction The anti-seasonal and continuous flooding precipitated loss of the original vegetation, especially trees and shrubs after the filling of the TGR. We found a significant decrease in the number of vascular plants compared to the pre-flooding period. The proportion of annual herbs, especially Compositae, Gramineae and Leguminosae plants have significantly increased in the riparian forest as a result of their adaptation strategies. And we found some invasive plants such as E. annuus began to show dominance in the vegetation composition of the new riparian forest in the TGR. The TGR area is not only one of the most biodiverse areas in China, but also one of the most endemic species areas in the world (Jin et al., 1984). The dominance of invasive plants can cause great harm to the gene pool and genetic diversity in the TGR area (Yang et al., 2012; Ge et al., 2020). The present results showed the high heterogeneity of species diversity and environmental factors in the TGR areas with significant habitat changes and poor ecosystem stability. Therefore, there may be some differences in the governance strategies adopted in different areas of the novel riparian ecosystem for vegetation restoration of the riparian forests. According to the comparative analysis of the vegetation status in the TGR area, the following four implications are proposed: ( 1 ) more attentions should be given to the indigenous species in the selection of species for the restoration and reconstruction of the novel riparian forests. The exploration and study of indigenous species in the reservoir may be a more effective and safe means of artificial vegetation restoration. Therefore, the above- described indigenous plant guilds should be prioritized in vegetation restoration efforts; ( 2 ) differences between regions should be taken into account in the implement of vegetation restoration measures in the reservoir area. The construction of artificial guilds during vegetation restoration should be tailored to the local context and plant adaptations to local conditions; ( 3 ) in general, when the artificial guilds are restored in the reservoir area, it may have a better effect with herbaceous plants as the main part, supplemented by shrubs or small trees in the middle-high elevation areas such as Distylium chinense (Sun et al., 2020) and Taxodium distichum (Li et al., 2010); ( 4 ) studies have shown that stabilization of vegetation in the depression zone may take 70 years or more (Nilsson & Aradóttir, 2013; Nilsson et al., 2013; Nilsson et al., 1997; Nilsson et al., 2015). Although it has been 19 years since the formation of the WFLZ of the TGR, the niche differentiation between different dominant plants was lower, the inter-specific competition was more intense and the stability of plant guilds was still worse. Therefore, long term investigations and observations should be continued in this area to identify and monitor alterations in the characteristics of the plant guilds and soil properties due to anti-seasonal and continuous inundation on riparian areas triggered by flow regulation or global warmer climates. 5. Conclusions In the present study a total of 73 vascular plants were identified in the WLFZ. There were significant differences in the species number and species diversity index in the different elevation areas. These diversity indexes increased along elevation gradients. The dominant species of plants varied with elevation, but C. dactylon always be the most dominant. And high niche breadth had a high niche overlap between species. Therefore, anti-seasonal water level rhythms precipitate substantial reduction of plant diversity, species competition and exclusion among species by expanding the niche in the guilds. Thus, the vegetation in the unique riparian ecosystems still was in the primary stage of plant community succession with low species diversity, high niche overlap, intense competition, and obvious single-species dominant communities. In addition, the spatial distribution of the plant guilds and niche characteristics were mainly influenced by the hydrological alterations (different flooding depths and flooding time) and the second factors were TN, TP, and OM. Annual herbs are better adapted to the fragmentation of the RWLFZ than perennial herbs, so it is suggested that the general policy of restoring and constructing artificial communities in the reservoir area should be mainly herbaceous, supplemented by shrubs or small trees. In order to establish a complete reference system for vegetation restoration, natural vegetation monitory plots in the different succession stages should be established in the different water level fluctuation zones of the TGR, and their environmental conditions, community structures and inter-specific relationships analyzed. Declarations Authors’ contributions Xiaoling Li,Xiaodie Duan and Wenxiong Yi:Writing-original draft. Wenxiong Yi and Xiaodie Duan:Conceptualization;Data curation;Formal analysis.Gong Chen, Jin Yang and Danli Deng:Investigation; Methodology; Software. Xiaojuan Guo and Zhengjian Yang:Project ministration;Resources;Fundingacquisition; Supervision. Guiyun Huang, Meixiang Hu, Chen Ye:the writing-reviewing and editing. Data availability The authors confirm that the data supporting the findings of this study are available within the article. Raw data that support the findings of this study area available from the corresponding author upon responsible request. Funding This work was supported by the National Natural Science Foundation of China (No. 51779127), partially funded by the Youth Innovation Promotion Association of the Chinese Academy of Sciences (No.2019334) and Research Project on Seed Preservation Technology and Facilities of Rare Plants in the Three Gorges Reservoir Area--Investigation and Collection of Flooding-Tolerant germplasm resources (SDHZ2021346). Acknowledgements We thank Jitan Liu, Wenqiang Wang, Wei Shi, Lei Sun, Ling Xiang, for their assistance during fieldwork. Ethics approval and consent to participate This study did not involve any animal or human testing. Conflict of interest The authors declare that they have no competing interests. Consent for publication Not applicable. References Aerts R, De Caluwe H, Beltman B. Is the relation between nutrient supply and biodiversity co‐determined by the type of nutrient limitation?. 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Vegetation of the water-level fluctuation zone in the Three Gorges Reservoir at the initialimpoundment stage. Global Ecology and Conservation. 2020;21:e00866. https.//doi.org/10.1016/j.gecco.2019.e00866 Additional Declarations No competing interests reported. Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-4053112","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":281884913,"identity":"7958f121-cef5-41b2-8663-161f8f93cc2c","order_by":0,"name":"Xiaoling Li","email":"","orcid":"","institution":"China Three Gorges University","correspondingAuthor":false,"prefix":"","firstName":"Xiaoling","middleName":"","lastName":"Li","suffix":""},{"id":281884914,"identity":"3aa74ffd-60f6-4826-b78c-1fb826fd9b89","order_by":1,"name":"Wenxiong Yi","email":"","orcid":"","institution":"China Three Gorges University","correspondingAuthor":false,"prefix":"","firstName":"Wenxiong","middleName":"","lastName":"Yi","suffix":""},{"id":281884915,"identity":"8b312009-54c6-4e90-931e-a33db4545be5","order_by":2,"name":"Xiaodie Duan","email":"","orcid":"","institution":"China Three Gorges University","correspondingAuthor":false,"prefix":"","firstName":"Xiaodie","middleName":"","lastName":"Duan","suffix":""},{"id":281884916,"identity":"04f2c137-b203-40d6-aa5d-ab4045f4fcd2","order_by":3,"name":"Gong Chen","email":"","orcid":"","institution":"China Three Gorges University","correspondingAuthor":false,"prefix":"","firstName":"Gong","middleName":"","lastName":"Chen","suffix":""},{"id":281884917,"identity":"2e38bd5e-39f9-4dcf-99ef-84b30c3abdd1","order_by":4,"name":"Jin Yang","email":"","orcid":"","institution":"China Three Gorges University","correspondingAuthor":false,"prefix":"","firstName":"Jin","middleName":"","lastName":"Yang","suffix":""},{"id":281884918,"identity":"813619b0-c0d7-4831-a420-3e1dcbb85c22","order_by":5,"name":"Danli Deng","email":"","orcid":"","institution":"China Three Gorges University","correspondingAuthor":false,"prefix":"","firstName":"Danli","middleName":"","lastName":"Deng","suffix":""},{"id":281884919,"identity":"703d2659-9783-4c45-8520-27c99c74106a","order_by":6,"name":"Xiaojuan Guo","email":"","orcid":"","institution":"China Three Gorges University","correspondingAuthor":false,"prefix":"","firstName":"Xiaojuan","middleName":"","lastName":"Guo","suffix":""},{"id":281884920,"identity":"e6ee7ca8-a584-4926-8133-448e3f3fe723","order_by":7,"name":"Zhengjian Yang","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAABB0lEQVRIiWNgGAWjYNACHgk5fobDB6C8BKK0WBhLNh5LYDhAvBaGisQNh88YEKfF4PjZwy9/yEgkzmw78/Hzh1+HGfjZcwwYfu7Ao+VMXpqFBI+EcT/P2c0SB/sOM0j2vDFg7D2DR8uBHDMDAx4J2Zkzzm5jONhzmMHgRo4BM2MbHi3n35gZJPBIMG64/+YZWIs9QS03cowfHOCRUNxw4Awbw4EfQFskCGiRvPHGjLEB6BfJhmPGEmcb0nkkzjwrONiLRwvf+Rzjjz976kBR+fBDxR9rOf725I0PfuLRonCAgU2CsQfKA7qHB0QfwK2BgUG+gYH5A8MPGPcPPrWjYBSMglEwUgEAUzlc1Zz1vS4AAAAASUVORK5CYII=","orcid":"","institution":"China Three Gorges University","correspondingAuthor":true,"prefix":"","firstName":"Zhengjian","middleName":"","lastName":"Yang","suffix":""},{"id":281884921,"identity":"253b4b51-c973-4f82-8315-a22662c161e3","order_by":8,"name":"Guiyun Huang","email":"","orcid":"","institution":"China Three Gorges Corporation","correspondingAuthor":false,"prefix":"","firstName":"Guiyun","middleName":"","lastName":"Huang","suffix":""},{"id":281884922,"identity":"404ad04d-c9e9-4304-a460-79a5e8e61e4f","order_by":9,"name":"Meixiang Hu","email":"","orcid":"","institution":"China Three Gorges Corporation","correspondingAuthor":false,"prefix":"","firstName":"Meixiang","middleName":"","lastName":"Hu","suffix":""},{"id":281884923,"identity":"7e8056c6-fa33-4390-9e1b-218233ca6960","order_by":10,"name":"Chen Ye","email":"","orcid":"","institution":"Wuhan Botanical Garden","correspondingAuthor":false,"prefix":"","firstName":"Chen","middleName":"","lastName":"Ye","suffix":""}],"badges":[],"createdAt":"2024-03-09 07:47:09","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-4053112/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-4053112/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":53278908,"identity":"4413084d-dc6e-46e7-ac66-d304bd872225","added_by":"auto","created_at":"2024-03-22 18:53:09","extension":"jpg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":102458,"visible":true,"origin":"","legend":"\u003cp\u003eThe study area in the water-level-fluctuation zone of the TGR, China.\u003c/p\u003e\n\u003cp\u003e1-3. Wujiang; 4-6. Zhongxian; 7-9. Wanzhou; 10-12. Pengxi River; 13-15. Tangxi River; 16-18. Meixi River; 19-21. Daxi River; 22-24. Daning River; 25-27. Tongzhuang River；28-30. Xiangxi River..\u003c/p\u003e","description":"","filename":"1.jpg","url":"https://assets-eu.researchsquare.com/files/rs-4053112/v1/483ef320ca264ce61f386964.jpg"},{"id":53279447,"identity":"cf20f9d4-7f6c-43f9-9e13-fb4e368323f5","added_by":"auto","created_at":"2024-03-22 19:01:10","extension":"jpg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":40430,"visible":true,"origin":"","legend":"\u003cp\u003eFamilies composition among three altitude sections in the water level fluctuation zone of the TGR. (n=105 for 145-155 m; n=132 for 155-165 m; n=129 for 165-175 m).\u003c/p\u003e","description":"","filename":"2.jpg","url":"https://assets-eu.researchsquare.com/files/rs-4053112/v1/bc80489f3fa23dd04dbd8aab.jpg"},{"id":53278909,"identity":"c3385676-c185-412f-afbb-c71f7ea104a7","added_by":"auto","created_at":"2024-03-22 18:53:09","extension":"jpg","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":62732,"visible":true,"origin":"","legend":"\u003cp\u003ePlant diversity among different altitude sections in the WLFZ of the TGR. Values are means ± SE. Different letters indicate statistically significant differences among the three altitude sections (n=105 for 145-155 m; n=137 for 155-165 m; n=126 for 165-175 m).\u003c/p\u003e","description":"","filename":"3.jpg","url":"https://assets-eu.researchsquare.com/files/rs-4053112/v1/5b6ed2fa6646fb594df913a0.jpg"},{"id":53278907,"identity":"ae9b0aab-02b6-4dd7-9254-d79f6b49a7d1","added_by":"auto","created_at":"2024-03-22 18:53:09","extension":"jpg","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":69215,"visible":true,"origin":"","legend":"\u003cp\u003eThe spatial dynamics of plant diversities from upstream to downstream in the WLFZ of the TGR. Regression analysis was used to investigate the spatial distribution pattern for each parameter and one-way ANOVA was used to examine the differences among the different sampling sites. 1. Wujiang; 2. Zhongxian; 3. Wanzhou; 4. Pengxi River; 5. Tangxi River; 6. Meixi River; 7. Daxi River; 8. Daning River; 9. Xiangxi River; 10. Tongzhuang River.\u003c/p\u003e","description":"","filename":"4.jpg","url":"https://assets-eu.researchsquare.com/files/rs-4053112/v1/fc3c0cfb59cdd7212395653a.jpg"},{"id":53278912,"identity":"f59ffdb4-0dca-48d8-afc3-b9452afd554e","added_by":"auto","created_at":"2024-03-22 18:53:10","extension":"jpg","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":52354,"visible":true,"origin":"","legend":"\u003cp\u003eFusion level diagram of four different clustering results.\u003c/p\u003e","description":"","filename":"5.jpg","url":"https://assets-eu.researchsquare.com/files/rs-4053112/v1/d4213a808f4068ab678d4026.jpg"},{"id":53278913,"identity":"e07e5a05-149a-4d8d-8ffd-9cb720850ca0","added_by":"auto","created_at":"2024-03-22 18:53:10","extension":"jpg","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":208584,"visible":true,"origin":"","legend":"\u003cp\u003eA heatmap of cluster tree of plant guilds on the distance matrix in the WLFZ.\u003c/p\u003e\n\u003cp\u003e1. Ass.Eclipta prostrata+Cynodon dactylon; 2. Ass.Bidens pilosa; 3. Ass.Bidens tripartita; 4. Ass.Digitaria sanguinalis; 5. Ass.Echinochloa crusgalli+Digitaria sanguinalis+Setaria viridis; 6. Ass.Humulus scandens; 7. Ass.Setaria viridis; 8. Ass.Cynodon dactylon+Abutilon theophrasti+Salvia plebeia; 9. Ass.Cynodon dactylon; 10. Ass.Conyza canadensis+Bidens pilosa; 11. Ass.Cynodon dactylon+Melilotus officinalis; 12. Ass.Cynodon dactylon+Echinochloa crusgalli+Cyperus rotundus.\u003c/p\u003e","description":"","filename":"6.jpg","url":"https://assets-eu.researchsquare.com/files/rs-4053112/v1/71746209c0ebf4a7999dd34b.jpg"},{"id":53278914,"identity":"7f92c57c-e04e-4e4d-8b8b-3a43c9e73089","added_by":"auto","created_at":"2024-03-22 18:53:10","extension":"jpg","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":89936,"visible":true,"origin":"","legend":"\u003cp\u003eThe heterogeneity of soil environmental factors in different habitats in the TGR.\u003c/p\u003e\n\u003cp\u003eLow altitude. 145-155 m; Middle altitude. 155-165 m; High altitude. 165-175 m. Values are means ± SE. SM, soil moisture; OM, organic matte; TN, total nitrogen; NO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e-\u003c/sup\u003e, nitrate; NH\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e+\u003c/sup\u003e, ammonium; TP, total phosphorus; AP, available phosphorus.\u003c/p\u003e","description":"","filename":"7.jpg","url":"https://assets-eu.researchsquare.com/files/rs-4053112/v1/4b027d625b1c3f5c3826cd01.jpg"},{"id":53278916,"identity":"602d99df-d4a6-42bc-95a3-bb9626d50601","added_by":"auto","created_at":"2024-03-22 18:53:11","extension":"jpg","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":51394,"visible":true,"origin":"","legend":"\u003cp\u003eOrdination diagram showed the result of CCA analysis of the important value index of (a) sampling sitesand environment variables, (b) species and environmental variables, and (c) sampling sites and plant species in the WLFZ of the TGR.\u003c/p\u003e","description":"","filename":"8.jpg","url":"https://assets-eu.researchsquare.com/files/rs-4053112/v1/34418a7de74e983137655c5c.jpg"},{"id":53278910,"identity":"2cc44091-a6f7-4809-b1f6-123ab9fad71d","added_by":"auto","created_at":"2024-03-22 18:53:10","extension":"jpg","order_by":9,"title":"Figure 9","display":"","copyAsset":false,"role":"figure","size":78335,"visible":true,"origin":"","legend":"\u003cp\u003eCorrelation between niche breadth and important value in WLFZ with elevations.\u003c/p\u003e","description":"","filename":"9.jpg","url":"https://assets-eu.researchsquare.com/files/rs-4053112/v1/6ca1161cf5b9b51f6b912637.jpg"},{"id":53278915,"identity":"af15ccdf-244f-4556-896c-eadd8efcd8f7","added_by":"auto","created_at":"2024-03-22 18:53:11","extension":"jpg","order_by":10,"title":"Figure 10","display":"","copyAsset":false,"role":"figure","size":219234,"visible":true,"origin":"","legend":"\u003cp\u003eNiche overlap values for dominant herbaceous plants in the 145-175 m altitude section in water-level-fluctuating zone.\u003c/p\u003e\n\u003cp\u003e145-155 m. 1. Cynodon dactylon; 2. Cyperus rotundus; 3. Xanthium sibiricum; 4. Polygonum hydropiper; 5. Echinochloa crusgalli; 6. Bidens pilosa; 7. Alternanthera philoxeroides; 8. Abutilon theophrasti; 9. Bidens tripartita; 10. Eclipta prostrata; 11. Ammannia baccifera; 12. Acalypha australis; 13. Digitaria sanguinalis; 14. Setaria viridis; 15. Cyperus difformis; 16. Portulaca oleracea; 17. Eleusine indica; 18. Solanum nigrum; 19. Salvia plebeia; 20. Phyllanthus urinaria; 21. Lindernia procumbens; 22. Artemisia argyi; 23. Aeschynomene indica; 24. Eriochloa villosa; 25. Vigna radiata; 26. Amaranthus retroflexus; 27. Humulus scandens; 28. Chenopodium ambrosioides; 29. Aster tataricus; 30. Torulinium ferax; 31. Lindernia crustacea; 32. Sida acuta; 33. Physalis alkekengi; 34. Erigeron annuus; 35. Euphorbia humifusa; 36. Ageratum conyzoides; 37. Rorippa indica; 38. Leucaena leucocephala.\u003c/p\u003e\n\u003cp\u003e155-165 m. 1. Cynodon dactylon; 2. Xanthium sibiricum; 3. Echinochloa crusgalli; 4. Setaria viridis; 5. Cyperus rotundus; 6. Bidens pilosa; 7. Digitaria sanguinalis; 8. Polygonum hydropiper; 9. Abutilon theophrasti; 10. Eclipta prostrata; 11. Solanum nigrum; 12. Acalypha australis; 13. Bidens tripartita; 14. Alternanthera philoxeroides; 15. Eriochloa villosa; 16. Euphorbia humifusa; 17. Erigeron annuus; 18. Eleusine indica; 19. Humulus scandens; 20. Melilotus officinalis; 21. Ageratum conyzoides; 22. Aeschynomene indica;23. Cyperus difformis; 24. Phyllanthus urinaria; 25. Artemisia argyi; 26. Physalis alkekengi; 27. Sesbania cannabina; 28. Artemisia carvifolia; 29. Bupleurum longiradiatum; 30. Dactyloctenium aegyptium; 31. Juncus effusus; 32. Phyla nodiflora; 33. Portulaca oleracea; 34. Anemarrhena asphodeloides; 35. Cosmos bipinnata; 36. Ambrosia artemisiifolia; 37. Conyza canadensis; 38. Amaranthus retroflexus; 39. Salvia plebeia; 40. Chenopodium ambrosioides; 41. Pouzolzia zeylanica; 42. Corydalis pallida; 43. Euphorbia helioscopia.\u003c/p\u003e\n\u003cp\u003e165-175 m. 1.Cynodon dactylon; 2. Xanthium sibiricum; 3. Setaria viridis; 4. Digitaria sanguinalis; 5. Bidens pilosa; 6. Melilotus officinalis; 7. Eclipta prostrata; 8. Echinochloa crusgalli; 9. Eriochloa villosa; 10. Polygonum hydropiper; 11. Alternanthera philoxeroides; 12. Bidens tripartita; 13. Cyperus rotundus; 14. Abutilon theophrasti; 15. Solanum nigrum; 16. Acalypha australis; 17. Conyza canadensis; 18. Eleusine indica; 19. Pouzolzia zeylanica; 20. Amaranthus retroflexus; 21. Ageratum conyzoides; 22. Cyperus difformis; 23. Arachis hypogaea; 24. Anemarrhena asphodeloides; 25. Artemisia argyi; 26. Humulus scandens; 27. Artemisia carvifolia; 28. Erigeron annuus; 29. Mazus japonicus; 30. Alopecurus aequalis; 31. Euphorbia humifusa; 32. Aeschynomene indica; 33. Aster tataricus; 34. Salvia plebeia; 35. Vigna radiata; 36. Hemistepta lyrata; 37. Vetiveria zizanioides; 38. Ambrosia artemisiifolia; 39. Phyllanthus urinaria; 40. Celosia argentea; 41. Sorghum bicolor; 42. Daucus carota; 43. Leptochloa chinensis; 44. Pilea cavaleriei; 45. Physalis alkekengi; 46. Mosla scabra; 47. Artemisia capillaris; 48. Euphorbia hypericifolia; 49. Lindernia crustacea; 50. Arthraxon hispidus; 51. Trigonotis peduncularis; 52. Mimosa pudica; 53. Commelina communis; 54. Vicia sepium; 55. Medicago sativa; 56. Cucumis sativus; 57. Erigeron acer.\u003c/p\u003e","description":"","filename":"10.jpg","url":"https://assets-eu.researchsquare.com/files/rs-4053112/v1/4876bec0cce57a554b1f1b3a.jpg"},{"id":53279687,"identity":"45f461b6-d13c-4b05-b49f-c01aa5058e77","added_by":"auto","created_at":"2024-03-22 19:09:16","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1232803,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-4053112/v1/388593d5-44a8-4eb1-8bc6-510c776a8b3a.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Anti-seasonal flooding drive substantial alterations in riparian plant diversity and niche characteristics in a unique hydro-fluctuation zone","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eGlobal warming and anthropogenic disturbance such as dam constructions are associated with an increase in flooding events, making many ecosystems worldwide vulnerable to submergence and flooding (Pucciariello \u0026amp; Perata, 2012, Xiao et al., 2022), which are major abiotic stresses for plants as significant determinants of plant species distribution worldwide, functions of plant guilds, forest community composition, structure and dynamics (Jackson \u0026amp; Colmer, 2005). Hirabayashi et al., (2013) also reported that a warmer climate would increase the risk of floods. What\u0026rsquo;s more, alterations of hydrological regimes and floods owing to the joint effects of operation of reservoirs and warmer climates play an important role in regulating the foristic composition, species diversity patterns and niche characteristics of riparian forest (Jian et al., 2017; Su et al., 2020). As the floodwaters move onto the riparian area, the soils became hypoxic, even resulting in severe anaerobism for plant roots, which posing a threat to the distribution of riparian forest plants without specific traits to adapt to anaerobic condition and ultimately lead to plant death (Gibbs \u0026amp; Greenway, 2003). Consequently, the unnaturally flooding (winter flooding) and prolonged inundation duration (nearly half a year) would remarkably influence the plant guilds, the plant community composition, species diversity pattern, niche characteristics and patterns of resource utilization of riparian forest. And plants growing in riparian zones are essential indicators of the ecosystem stability of riparian habitats. Therefore, it has crucial ecological significance to evaluate influences of anti-seasonal long flooding on the plant guilds and niche characteristics of plant communities in the newly formed aquatic\u0026ndash;terrestrial interface for vegetation restoration and reconstruction in the riparian forest. However, the response of riparian vegetation by the niche characteristics to such unnaturally continuous flooding environment is less documented.\u003c/p\u003e \u003cp\u003eTo understand resource utilization status and ecological adaptability of various plant populations in different environments and provide references for biodiversity conservation and vegetation restoration efforts in degraded riparian forest ecosystem, the niche theory were introduced and has become one of the fundamental theories to explain species coexistence and competition in natural plant guilds (Slatye et al. 2013; Cui et al., 2013; Jian et al., 2017; D\u0026rsquo;Andrea et al., 2020). Niche involves two complementary aspects. one relates to the space occupied by a group of species or a guild in the ecological space and the other relates to resource utilization and competition among coexisting species (Lakkis, 1994). Niche breadth measures the range of resource characteristics across which a species exists, and indicates the extent that species utilize different types of resources. Niche overlap has often been used as a measure of potential competition between species (Milne \u0026amp; Mason, 1990), because it is expected to determine how many and which species can coexist in a guild. Previous studies found that species with similar patterns of resource utilization (i.e., species of the same guilds) were susceptible to competitive interactions that affect the community structure (P\u0026eacute;rez-Crespo et al., 2013). Patterns of resource utilization (either food or habitat resources) were normally analyzed in the framework of niche theory, i.e., members of the same guilds similarly exploit similar resources and may be underlying competitors. It is generally agreed that the number of related species that can coexist in a given community depends on the niche widths of the several species and the degree to which their niches overlap (Pielou, 1972). To explore ecological processes, such as competition over shared resources, both niche breadth and niche overlap provide indirect ways (MacNally, 1983). Moreover, the environmental impacts on the plant community also reflects the adaptation and evolution of the plant community to its conditions. Plant communities that inhabit aquatic ecosystems usually have a complex structure driven by a large number of variables that influence plant-plant interactions (Winemiller \u0026amp; Pianka, 1990). So, it is necessary to evaluate the available resources and the relative amounts of inter- and intra-specific competition by niche width and overlap among the coexisting species of the community in specific environments such as in a novel hydro-fluctuation zone.\u003c/p\u003e \u003cp\u003eAs the largest hydropower project in the world, the Three Gorges Dam (TGD) on the Yangtze River was initiated in 1994 (Zhang et al., 2013), and first impoundment occurred in June 2003 (Yang et al., 2012). The water level of the reservoir fluctuates from 145 m in summer (May to September) to 175 m in winter (October to April), resulting in the formation of a water level fluctuation zone (WLFZ) with an area of 350 km\u003csup\u003e2\u003c/sup\u003e in the reservoir (Ye et al., 2013). The hydrological regime of the Three Gorges Reservoir (TGR) was the exact opposite of the natural flood rhythms of the Yangtze River (Fan et al., 2012), which formed a unique riparian ecosystem. Before the impoundment of the TGR, the main vegetation types of riparian forests in the zone below an elevation of 175 m were trees (e.g., \u003cem\u003ePinus massoniana\u003c/em\u003e and \u003cem\u003eCupressus funebris\u003c/em\u003e), shrubs (e.g., \u003cem\u003eVitex negundo\u003c/em\u003e, \u003cem\u003eSecurinega suffruticosa\u003c/em\u003e and \u003cem\u003eMyricaria laxiflora\u003c/em\u003e) and herbs (\u003cem\u003eImperata cylindrica\u003c/em\u003e, \u003cem\u003eArthraxon hispidus\u003c/em\u003e and \u003cem\u003eCynodon dactylon\u003c/em\u003e) (Chen et al., 2008). After the filling of the TGR, the reversal of submergence time and prolonged inundation duration precipitated the loss of previous vegetation, and annual plants such as \u003cem\u003eSetaria viridis\u003c/em\u003e, \u003cem\u003eDigitaria ciliaris\u003c/em\u003e, and \u003cem\u003eComnyza canadensis\u003c/em\u003e currently became dominant species (Lu et al., 2010; Ye et al., 2013). According to the plant species distribution survey from the WLFZ in the TGR in 2009, the decreased ratio of plant families, genera, and species of post-dam riparian vegetation in 2009 was 26.51%, 29.58% and 42.96%, respectively, compared with the pre-dam riparian plant species in 2001 (Liu et al., 2011). The vegetation investigation of the Pengxi River, Baijia Stream and Xiangxi River in the TGR also showed that the vegetation in the WLFZ of the TGR was seriously degenerated, the community structure was single and the species richness and diversity decreased (Liu et al., 2011; Yuan et al., 2014; You et al., 2017; Xiang, et al., 2020; Li, et al., 2022). The hydrological alterations greatly degraded biodiversity in the TGR disturbance zone, particularly the disappearance of indigenous vegetation significantly would undermine the function of the regional ecosystem service (Zhu et al., 2020). Vegetation restoration in the WLFZ has become an increasing concern in recent years (Ye et al., 2013; Gong et al., 2023; Zhang et al., 2016). Thus, it is important to understand the plant community characteristics in the novel riparian forest. However, there was a lack of application of niche theory to explore its formation mechanism of plant community, which is always a key issue for plant community ecologist.\u003c/p\u003e \u003cp\u003eAs described above, there have been some reports on plant community characteristics of the WLFZ at the beginning of the impoundment period of the TGR (Su et al., 2020; Zhang et al., 2013; Ye et al., 2013). However, little is known on how anti-seasonal and continuous flooding hydrological alterations affect the riparian guilds, from functional and niche perspectives, of the unique drawdown zone vegetation after 19 times of operation of the TGR.\u003c/p\u003e \u003cp\u003eThe TGR catchment provides a unique scenario to investigate the functional response of riparian herbaceous species to the novel anti-seasonal and continuous flooding environments across a 600 km stream gradient in a globally-significant river system. We randomly selected 30 reaches along the shorelines of the TGR subjected to anti-seasonal and continuous flooding. Fieldwork was conducted after 19 times of operation of the TGR in order to answer the following questions. (\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e) What were specific plant community characteristics and functional diversity in the unique riparian ecosystem after 19 times of operation of the TGR? (\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e) Which plant guilds were favoured or disfavoured by the novel anti-seasonal and continuous flooding environment? and (\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e) how did the niche characteristics of dominant species change in various flooding environments, especially along an elevation gradient in the TGR? Accordingly, we hypothesized that (\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e) anti-seasonal flooding substantially altered the plant community characteristics and species diversity patterns, and reduced species diversity in the the novel riparian ecosystem of the TGR, (\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e) the more niche breadth of dominant plant species in the unique riparian ecosystem would imply that they would utilize more limited resources and the more niche overlap would show the more inter-specific competition and co-existence in the plant community and (\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e) anti-seasonal and continuous flooding would precipitate the gradual disappearance of the original diverse niches, resulting in more uniform habitats, and there was obvious competition among species with similar resource requirements. This work will help to provide optimal plant guild selection and scientific plant configuration for ecological restoration efforts in the novel riparian forest of the TGR region and the similar ecologically fragile areas.\u003c/p\u003e"},{"header":"2. Materials and Methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\n \u003ch2\u003e2.1 Study area\u003c/h2\u003e\n \u003cp\u003eThe TGR region (29\u0026deg;16\u0026prime; to 31\u0026deg;25\u0026prime;N, 106\u0026deg; to 111\u0026deg;50\u0026prime;E) lies in a 600-km valley from Yichang to upstream Chongqing, China (Fig. \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e). This area is characterized by a subtropical monsoon climate, with an annual mean temperature of 16.5\u0026ndash;19.0℃ and annual mean precipitation ranging from 886 to 1614 mm, 80% of which occurs between April and October (Ye et al., 2011). The soil is purple soil consisting of 29% sand, 49% silt and 22% clay in the top 20 cm. Our study area is located in the water level fluctuation zone of the TGR, where the water level fluctuates from 145 m a.s.l. in summer to 175 m a.s.l. in winter (Ye et al., 2015). Summer is the raining season in the study area which results in seasonal water level fluctuations that temporally range between 145 m and 155 m with flooding periods lasting from a few days to approximately two weeks (Wang et al., 2014). However, due to the regulation of the TGR, the highest water level rise occurs in winter and falls to the lowest level in summer in an annual cycle. These changes in water level fluctuation are opposite to natural seasonal fluctuations and are called \u0026ldquo;anti-seasonal\u0026rdquo; (Willison et al., 2013). The duration of anti-seasonal flooding differs according to elevation (i.e., 145\u0026mdash;155 m a.s.l. with an average inundation duration of 286 days per year; 155\u0026mdash;165 m a.s.l., with an average inundation duration of 237 days per year; and 165\u0026mdash;175 m a.s.l., with an average inundation of 169 days per year).\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec4\" class=\"Section2\"\u003e\n \u003ch2\u003e2.2 Vegetation investigation\u003c/h2\u003e\n \u003cp\u003eInvestigation was conducted in August to September, just before the rise in the wate rlevel in the TGR. At this time of the year, the vegetation in the water level fluctuation zones (WLFZs) was exposed and maximally recovered from the preceding flood, which occurred in the summer, autumn, and winter in the WLFZs. Sample transects with 50 m lengths were defined and were parallel to the water level gradient. Within the transects, 30 reaches were randomly selected along the shorelines of the TGR subjected to anti-seasonal and continuous flooding from upstream to downstream in the Reservoir \u003cstrong\u003ein 2022\u003c/strong\u003e. Among them, 24 sampling sites were located in the tributaries of the Yangtze River (1\u0026ndash;3; 10\u0026ndash;30) and 6 sampling sites were located in the mainstream (\u003cspan class=\"CitationRef\"\u003e4\u003c/span\u003e\u0026ndash;\u003cspan class=\"CitationRef\"\u003e9\u003c/span\u003e). At each sampling site we established a transect along an elevational gradient, from 145 m a.s.l to 175 m a.s.l. (i.e., bottom, 145\u0026ndash;155 m; middle, 155\u0026ndash;165 m; and top, 165\u0026ndash;175 m). Because flooding regime varies based on elevation, these transects allowed us to investigate the effects of flooding on riparian ecosystem properties. Five 1\u0026times;1 m herb quadrats were investigated in the three sections of each sampling site, the relative density, relative frequency, relative height and relative coverage. However, survey was only carried out between the elevations of 156\u0026ndash;165 m; 166\u0026ndash;175 m in Wujiang River and Zhongxian because of high water level during the sampling period. Therefore, a total of 368 plant quadrats were investigated. Each vegetation sample quadrat was a focal point for flora survey and the categorical traits were obtained and the plant species were identified from the Flora Reipublicae Popularis Sinicae (\u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttp.//www.iplant.cn/frps\u003c/span\u003e\u003c/span\u003e) and field observations. For each species in a quadrat, we recored all the individuals of a given species in each quadrat, measured the average height of 10 randomly selected individuals and measured the coverage by estimating the projective canopy area.\u003c/p\u003e\n \u003cp\u003eThe soil samples (0\u0026ndash;20 cm) was investigated using the cutting ring method. Three random topsoil samples (0\u0026ndash;20 cm) were collected and then mixed to form a composite sample at each elevation zone of each transect. A total of 129 mixed soil samples were sealed in plastic bags and brought to the laboratory. Soil samples were air-dried and sieved (\u0026lt;\u0026thinsp;2 mm) before analysis. The sketch map of study area and sampling sections were shown in Fig. \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec5\" class=\"Section2\"\u003e\n \u003ch2\u003e2.3 Environmental variable analysis\u003c/h2\u003e\n \u003cp\u003eSoil pH was determined in a 1.5 soil. solution ratio, using a combination glass electrode (Kabala \u0026amp; Musztyfaga, 2015). Soil organic matter (OM) was determined by potassium dichromate titrimetric solution with the method detection limit (MDL) of 0.5 g kg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e TN was determined by the Kjeldahl method. TP and AP were measured by molybdenum-antimony anti-spectrophotometric method. TK and AK were determined by flame photometric method (Bao. 2000). A 15-g sample of soil was extracted by shaking with 100 ml of 2 M KCl for 1 h. Exchangeable NH\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e+\u003c/sup\u003e-N and NO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e-\u003c/sup\u003e-N were determined with spectrophotometer using the Indophenol blue colorimetric method and Phenol disulfonic acid colorimetry, respectively (Ye et al., 2015). The heterogeneity of soil environmental factors in different elevations in the TGR are shown in Fig. \u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec6\" class=\"Section2\"\u003e\n \u003ch2\u003e2.4 Data analysis\u003c/h2\u003e\n \u003cdiv id=\"Sec7\" class=\"Section3\"\u003e\n \u003ch2\u003e2.4.1 Importance value\u003c/h2\u003e\n \u003cp\u003eThe importance values of different species at a given community were calculated on the basis of the relative coverage (RC), relative frequency (RF), relative height (RH) and the relative density (RD) of each species in different quadrats and then used as the indicators to determine the dominant herbaceous plant species in the WLFZs and the ecological niche measurement. The calculation formula is.\u003c/p\u003e\n \u003cp\u003eP\u003csub\u003ei\u003c/sub\u003e=(RC\u0026thinsp;+\u0026thinsp;RH\u0026thinsp;+\u0026thinsp;RF\u0026thinsp;+\u0026thinsp;RD)/4 (\u003cspan class=\"CitationRef\"\u003e1\u003c/span\u003e)\u003c/p\u003e\n \u003cp\u003eWhere P\u003csub\u003ei\u003c/sub\u003e is the importance value of the \u003cem\u003ei\u003c/em\u003e-th species, RC is the projective coverage of a given species divided by the total coverage of all the species in all the quadrats; RF is number of occurrence of the species divided by the total number of occurrence of all the species in all the quadrats, RH is average height of the species divided by the total height of all the species in all the quadrats and RD is the total number of individuals of the species in all quadrats divided by the total number of all the species in all the quadrats.\u003c/p\u003e\n \u003c/div\u003e\n \u003cdiv id=\"Sec8\" class=\"Section3\"\u003e\n \u003ch2\u003e2.4.2 Species diversity index\u003c/h2\u003e\n \u003cp\u003eFisher\u0026apos;s \u0026alpha;-diversity index was characterized by species number (\u003cem\u003eS\u003c/em\u003e), Shannon diversity index (\u003cem\u003eH\u003c/em\u003e), Pielou evenness index (\u003cem\u003eE\u003c/em\u003e), and Simpson dominance index (\u003cem\u003eD\u003c/em\u003e). The calculation formulas are (Curtis \u0026amp; McIntosh, 1951).\u003c/p\u003e\n \u003cp\u003eShannon diversity index: \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(H=-\\varSigma {P}_{i}ln{P}_{i}\\)\u003c/span\u003e\u003c/span\u003e (\u003cspan class=\"CitationRef\"\u003e2\u003c/span\u003e)\u003c/p\u003e\n \u003cp\u003ePielou evenness index: \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(E=\\frac{H}{ln\\text{S}}\\)\u003c/span\u003e\u003c/span\u003e (\u003cspan class=\"CitationRef\"\u003e3\u003c/span\u003e)\u003c/p\u003e\n \u003cp\u003eSimpson dominance index: \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(H=-\\varSigma {P}_{i}^{2}\\)\u003c/span\u003e\u003c/span\u003e (\u003cspan class=\"CitationRef\"\u003e4\u003c/span\u003e)\u003c/p\u003e\n \u003cp\u003eWhere \u003cem\u003eP\u003c/em\u003e\u003csub\u003e\u003cem\u003ei\u003c/em\u003e\u003c/sub\u003e is the importance value of the \u003cem\u003ei\u003c/em\u003e-th species, \u003cem\u003eS\u003c/em\u003e is the number of species appearing within the quadrat and \u003cem\u003eN\u003c/em\u003e is the total number of species present within the quadrats.\u003c/p\u003e\n \u003c/div\u003e\n \u003cdiv id=\"Sec9\" class=\"Section3\"\u003e\n \u003ch2\u003e2.4.3 Niche breadth\u003c/h2\u003e\n \u003cp\u003eThe niche breadth, as proposed by Levin, was calculated by Colwell\u0026apos;s modified formula (Feinsinger et al., 1981) :\u003c/p\u003e\n \u003cdiv id=\"Equ1\" class=\"Equation\"\u003e\n \u003cdiv class=\"mathdisplay\" id=\"FileID_Equ1\" name=\"EquationSource\"\u003e$${B}_{i}=\\frac{1}{r\\times \\sum _{\\text{h}=1}^{\\text{r}}{(P}_{ih}{)}^{2}}$$\u003c/div\u003e\n \u003cdiv class=\"EquationNumber\"\u003e5\u003c/div\u003e\n \u003c/div\u003e\n \u003cp\u003eWhere \u003cem\u003eB\u003c/em\u003e\u003csub\u003e\u003cem\u003ei\u003c/em\u003e\u003c/sub\u003e is the niche breadth of the \u003cem\u003ei\u003c/em\u003e-th species, \u003cem\u003eP\u003c/em\u003e\u003csub\u003e\u003cem\u003eih\u003c/em\u003e\u003c/sub\u003e is the ratio of the importance value of the \u003cem\u003ei\u003c/em\u003e-th species at the \u003cem\u003eh\u003c/em\u003e-th resource level to the sum of the importance values of the species at all resource levels, \u003cem\u003er\u003c/em\u003e is the number of resource levels, and the value range is [0,1].\u003c/p\u003e\n \u003c/div\u003e\n \u003cdiv id=\"Sec10\" class=\"Section3\"\u003e\n \u003ch2\u003e2.4.4. Niche overlap\u003c/h2\u003e\n \u003cp\u003eThe Pianka formula was used to calculate niche overlap (Pianka, 1974).\u003c/p\u003e\n \u003cdiv id=\"Equ2\" class=\"Equation\"\u003e\n \u003cdiv class=\"mathdisplay\" id=\"FileID_Equ2\" name=\"EquationSource\"\u003e$${O}_{ih}=\\frac{\\underset{h=1}{\\overset{r}{\\int }}{P}_{ih}{P}_{jh}}{\\sqrt{\\underset{h=1}{\\overset{r}{\\int }}{P}_{ih}^{2}\\underset{h=1}{\\overset{r}{\\int }}{P}_{jh}^{2}}}$$\u003c/div\u003e\n \u003cdiv class=\"EquationNumber\"\u003e6\u003c/div\u003e\n \u003c/div\u003e\n \u003cp\u003eWhere \u003cem\u003eO\u003c/em\u003e\u003csub\u003e\u003cem\u003eij\u003c/em\u003e\u003c/sub\u003e is the niche overlap of populations \u003cem\u003ei\u003c/em\u003e and \u003cem\u003ej\u003c/em\u003e, and \u003cem\u003ep\u003c/em\u003e\u003csub\u003e\u003cem\u003eih\u003c/em\u003e\u003c/sub\u003e and \u003cem\u003ep\u003c/em\u003e\u003csub\u003e\u003cem\u003eij\u003c/em\u003e\u003c/sub\u003e are the proportion of the importance values of the \u003cem\u003ei\u003c/em\u003e-th and the \u003cem\u003ej\u003c/em\u003e-th species at the \u003cem\u003eh\u003c/em\u003e-th resource level in the synthesis of the importance values of the species at all resource levels, and r is the number of resource levels, and the range of the formula is [0, 1].\u003c/p\u003e\n \u003c/div\u003e\n \u003cdiv id=\"Sec11\" class=\"Section3\"\u003e\n \u003ch2\u003e2.4.5. The total mean of niche overlap values\u003c/h2\u003e\n \u003cp\u003eThe total mean value of niche overlap value among all populations (\u003cem\u003eTAO\u003c/em\u003e\u003csub\u003e\u003cem\u003eih\u003c/em\u003e\u003c/sub\u003e) in the sample land is calculated as follows (Chen et al., 2019).\u003c/p\u003e\n \u003cdiv id=\"Equ3\" class=\"Equation\"\u003e\n \u003cdiv class=\"mathdisplay\" id=\"FileID_Equ3\" name=\"EquationSource\"\u003e$${TAO}_{ih}=\\frac{{TO}_{ih}}{TP}$$\u003c/div\u003e\n \u003cdiv class=\"EquationNumber\"\u003e7\u003c/div\u003e\n \u003c/div\u003e\n \u003cp\u003eWhere, \u003cem\u003eTO\u003c/em\u003e\u003csub\u003e\u003cem\u003eih\u003c/em\u003e\u003c/sub\u003e is the total number of niche overlap values among all populations in the sample plot, and \u003cem\u003eTP\u003c/em\u003e is the total species logarithm.\u003c/p\u003e\n \u003c/div\u003e\n \u003cdiv id=\"Sec12\" class=\"Section3\"\u003e\n \u003ch2\u003e2.4.6. Statistical analysis\u003c/h2\u003e\n \u003cp\u003eTwo-way clustering analysis provides a very visual picture of the distribution, classification, and degree of similarity between species in a community. In this study, we conducted clustering analysis of plant species in the surveyed quadrat, and calculated the significant values of the species in the sample to obtain the plant significant value matrix as the basis of clustering analysis according to the program method in \u0026quot;Quantitative Ecology-Application of the R Language\u0026quot;. The groups were designated as riparian guilds where each vegetation group comprising a guild. (\u003cspan class=\"CitationRef\"\u003e1\u003c/span\u003e) contains species sharing similar features; and (\u003cspan class=\"CitationRef\"\u003e2\u003c/span\u003e) shares a similar environment.\u003c/p\u003e\n \u003cp\u003eCanonical correspondence analysis (CCA) was used to analyze the data of 10 environmental factors from 10 sample sites in the TGR area and 31 plant species after excluding species with frequency less than 3 from the sample sites to get information such as the structure of the biological community, the relationship between the biological community and environmental factors. All the analyses were performed using SPSS 22.0 and Origin 2018 for Windows except the CCA which was performed using Canoco 5.0 and two-way clustering analysis used the program packages such as vegan, gclus and cluster in R software based on investigation in 2022.\u003c/p\u003e\n \u003c/div\u003e\n\u003c/div\u003e"},{"header":"3. Results","content":"\u003cdiv id=\"Sec14\" class=\"Section2\"\u003e\n \u003ch2\u003e3.1 Foristic composition\u003c/h2\u003e\n \u003cp\u003eA total of 73 vascular plant species were identified, belonging to 65 genera of 25 families, including 52 species of annual herbs, 20 species of perennial herbs and 1 species of shrub, accordingly accounting for 71.23%, 27.39% and 1.37% of the total number of species, respectively. The plant families with the largest number of species in the studied area were Compositae (N\u0026thinsp;=\u0026thinsp;15, 20.56%), Gramineae (\u003cem\u003eN\u003c/em\u003e\u0026thinsp;=\u0026thinsp;12, 16.45%), Leguminosae (\u003cem\u003eN\u003c/em\u003e\u0026thinsp;=\u0026thinsp;9, 12.32%), Euphorbiaceae (\u003cem\u003eN\u003c/em\u003e\u0026thinsp;=\u0026thinsp;5, 8.22%), respectively. A significant proportion of plants of single genus and species in the survey area were in 13 families (i.e., 13 genera and 13 species), representing 52% of the total number of families, 20% of the total number of genus and 17.8% of the total number of species, respectively.\u003c/p\u003e\n \u003cp\u003eThere were different plant species, genera, and families at different altitudes (145\u0026ndash;155, 155\u0026ndash;165, and 165\u0026ndash;175 m) in the WLFZ of the TGR. Individually, there were 38 vascular plant species belonging to 32 genera of 16 families at the 145\u0026ndash;155 m, 43 vascular plant species belonging to 39 genera of 19 families at the 155\u0026ndash;165 m and 57 vascular plant species belonging to 50 genera of 18 families at the 165\u0026ndash;175 m (Fig. \u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e). Species numbers significantly increased with increasing elevation. Annual herb was the dominant life form in the whole study area, accounting for 78.95% of plant species at the elevation intervals of 144\u0026ndash;155 m, 74.42% at the altitudes of 155\u0026ndash;165 m and 71.93% at the altitudes of 165\u0026ndash;175 m, respectively. The less frequent life form was perennial herb (145\u0026ndash;155 m. n\u0026thinsp;=\u0026thinsp;7, 18.42%; 155\u0026ndash;165 m. n\u0026thinsp;=\u0026thinsp;11, 25.58%; 165\u0026ndash;175 m. n\u0026thinsp;=\u0026thinsp;16, 28.07%). Compositae and Gramineae were the larger families with 6\u0026ndash;15 species than other ones and contributed to 37.01% of the total plant species in the current study (Fig. \u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e). The proportion of Compositae and Gramineae plants showed an upward trend with the increasing altitude. The proportion of annual herbs species showed a decreasing trend along altitude gradients, while the proportion of perennial herb species showed an opposite trend.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec15\" class=\"Section2\"\u003e\n \u003ch2\u003e3.3 Spatial variation in plant diversities\u003c/h2\u003e\n \u003cp\u003eThe \u003cem\u003eH\u003c/em\u003e values ranged from 0.831 to 1.661 in the WLFZ, increasing with the increasing altitude, of which the highest \u003cem\u003eH\u003c/em\u003e (1.458\u0026thinsp;\u0026plusmn;\u0026thinsp;0.035) appeared at the altitude of 165\u0026ndash;175 m. The \u003cem\u003eS\u003c/em\u003e and \u003cem\u003eD\u003c/em\u003e also showed a rising trend in spatial variation with altitude in the WLFZ, but the latter is not significant. However, the \u003cem\u003eE\u003c/em\u003e showed a contrary trend that E decreased with the increasing altitude (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.01, Fig. \u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003e).\u003c/p\u003e\n \u003cp\u003eThe \u003cem\u003eH\u003c/em\u003e, \u003cem\u003eD\u003c/em\u003e, \u003cem\u003eS\u003c/em\u003e and \u003cem\u003eE\u003c/em\u003e showed same trends in the spatial distribution patterns from upstream to downstream in the WLFZ of TGR, which firstly showed a significant increasing trend (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.05), reached the highest in the middle reaches in the Tangxi River, and then decreased in the downstream reaches (Wujiang River to Tongzhuang River) (Fig. \u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003e). And the \u003cem\u003eH\u003c/em\u003e, \u003cem\u003eE\u003c/em\u003e and \u003cem\u003eS\u003c/em\u003e reached the highest point at Tangxi River. In short, the spatial heterogeneity of the \u003cem\u003eH\u003c/em\u003e, \u003cem\u003eD\u003c/em\u003e, and \u003cem\u003eE\u003c/em\u003e for plants from upstream to downstream were strong in the TGR of the Yangtze River, and less for \u003cem\u003eS\u003c/em\u003e.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec16\" class=\"Section2\"\u003e\n \u003ch2\u003e3.4 Classification of guilds\u003c/h2\u003e\n \u003cp\u003eIn this study, the important values of species in the plant community were selected as the clustering basis. Four different clustering methods were used to cluster 368 quadrats (communities) in the WLFZ (Fig. \u003cspan class=\"InternalRef\"\u003e5\u003c/span\u003e). In order to interpret and compare the results of the four clustering analysis methods, we need to find the interpretable clusters. As the value of the difference between the two branches in the cluster tree, the fusion level value of the cluster tree can help to judge the clustering level of different clustering methods through analysis. The results of fusion level and clustering tree showed that the single link clustering was the most reasonable among the four clustering methods (Fig. \u003cspan class=\"InternalRef\"\u003e5\u003c/span\u003e).\u003c/p\u003e\n \u003cp\u003eThen, the single chain clustering method was selected to cluster 368 samples in the WLFZ of the TGR. By calculating the correlation between the original distance and the binary matrix representing different classification levels, the classification level corresponding to the highest correlation coefficient was selected as the optimal grouping scheme, and the results showed that it was the most reasonable to be divided into 12 guilds (Fig. \u003cspan class=\"InternalRef\"\u003e6\u003c/span\u003e). Each guild represented a plant community type, and it was named after the dominant species in the community. The naming format refers to the description of plant community naming in《Chinese Vegetation》(Wu, 1980). The 12 main plant guilds were discovered as followed.\u003c/p\u003e\n \u003cp\u003eGuild 1. Ass. \u003cem\u003eEclipta prostrata\u003c/em\u003e\u0026thinsp;+\u0026thinsp;\u003cem\u003eCynodon dactylon\u003c/em\u003e, hygrophyte and mesophyte community, flood-tolerant riparian herbs, including 5 samples and 16 species. The main companion species were \u003cem\u003eDigitaria sanguinalis\u003c/em\u003e, \u003cem\u003eEuphorbia humifusa\u003c/em\u003e, and \u003cem\u003eAcalypha australis\u003c/em\u003e, with a distribution range of 155\u0026ndash;175 m in elevation.\u003c/p\u003e\n \u003cp\u003eGuild 2. Ass. Bidens pilosa, \u003cstrong\u003ehygrophyte and mesophyte community\u003c/strong\u003e, competitive annual herbs, including 6 samples and 21 species. The companion species are Polygonum hydropiper, Amaranthus retroflexus, Echinochloa crusgalli, and Xanthium sibiricum, which were mainly found at elevations of 165\u0026ndash;175 m.\u003c/p\u003e\n \u003cp\u003eGuild 3. Ass. Bidens tripartita, \u003cem\u003ehygrophyte and mesophyte community\u003c/em\u003e, competitive annual herbs,including 3 samples and 13 species. The companion species are Xanthium sibiricum, Digitaria sanguinalis, Echinochloa crusgalli, Bidens pilosa, Cynodon dactylon, the main distribution altitude is 165\u0026ndash;175 m.\u003c/p\u003e\n \u003cp\u003eGuild 4. Ass. \u003cem\u003eDigitaria sanguinalis\u003c/em\u003e, \u003cem\u003ehygrophyte and mesophyte community\u003c/em\u003e, competitive annual herbs, including 9 samples and 18 species. The companion species are \u003cem\u003eSetaria viridis\u003c/em\u003e, \u003cem\u003eAcalypha australis\u003c/em\u003e, and \u003cem\u003eXanthium sibiricum\u003c/em\u003e, which were mainly distributed at an elevation of 165\u0026ndash;175 m.\u003c/p\u003e\n \u003cp\u003eGuild 5. Ass. Echinochloa crusgalli\u0026thinsp;+\u0026thinsp;Digitaria sanguinalis\u0026thinsp;+\u0026thinsp;Setaria viridis, \u003cem\u003emesophyte community\u003c/em\u003e, competitive riparian herbs, including 5 samples and 18 species. The companion species were Bidens pilosa, Xanthium sibiricum and Humulus scandens, which are mainly found at elevations of 145\u0026ndash;175 m.\u003c/p\u003e\n \u003cp\u003eGuild 6: Ass. \u003cem\u003eHumulus scandens\u003c/em\u003e, \u003cem\u003ehygrophyte and mesophyte community\u003c/em\u003e, competitive riparian herbs, including 2 samples and 8 species. The companion species are \u003cem\u003eBidens pilosa, Echinochloa crusgalli\u003c/em\u003e, \u003cem\u003eEleusine indica\u003c/em\u003e and \u003cem\u003eChenopodium ambrosioides\u003c/em\u003e which were mainly found at elevations of 165\u0026ndash;175 m.\u003c/p\u003e\n \u003cp\u003eGuild 7. Ass. Setaria viridis, \u003cem\u003ehygrophyte and mesophyte community\u003c/em\u003e, competitive riparian herbs, including 19 samples and 28 species. The companion species are Digitaria sanguinalis, Xanthium sibiricum, Bidens pilosa, and Cynodon dactylon and Eriochloa villosa, which were mainly found at elevations of 165\u0026ndash;175 m.\u003c/p\u003e\n \u003cp\u003eGuild 8: Ass. \u003cem\u003eCynodon dactylon\u003c/em\u003e\u0026thinsp;+\u0026thinsp;\u003cem\u003eAbutilon theophrasti\u003c/em\u003e\u0026thinsp;+\u0026thinsp;\u003cem\u003eSalvia plebeia\u003c/em\u003e, hygrophyte and mesophyte community, stress-tolerant woody and herb species, including 6 samples and 15 species. The companion species are \u003cem\u003eSolanum nigrum, Digitaria sanguinalis, Bidens pilosa\u003c/em\u003e and \u003cem\u003eSetaria viridis\u003c/em\u003e, which were mainly found at elevations of 165\u0026ndash;175 m.\u003c/p\u003e\n \u003cp\u003eGuild 9. Ass. \u003cem\u003eCynodon dactylon\u003c/em\u003e, hygrophyte and mesophyte community, flood-tolerant riparian herbs, including 293 samples and 62 species. The companion species are \u003cem\u003eXanthium sibiricum, Echinochloa crusgalli, Cyperus rotundus\u003c/em\u003e, and \u003cem\u003eBidens pilosa\u003c/em\u003e, which were mainly found at elevations of 145\u0026ndash;175 m.\u003c/p\u003e\n \u003cp\u003eGuild 10. Ass. Conyza canadensis\u0026thinsp;+\u0026thinsp;Bidens pilosa, \u003cem\u003ehygrophyte and mesophyte community\u003c/em\u003e, competitive annual herbs, including 11 samples and 20 species. The companion species are Artemisia argyi, Setaria viridis, Echinochloa crusgalli and Eriochloa villosa, which were mainly found at elevations of 165\u0026ndash;175 m.\u003c/p\u003e\n \u003cp\u003eGuild 11. Ass. Cynodon dactylon\u0026thinsp;+\u0026thinsp;Melilotus officinalis, \u003cem\u003ehygrophyte and mesophyte community\u003c/em\u003e, stress-tolerant herb and woody species, including 6 samples and 15 species. The companion species were Setaria viridis, Anemarrhena asphodeloides, Echinochloa crusgalli, Bidens pilosa and Abutilon theophrasti, which are mainly found at elevations of 155\u0026ndash;175 m.\u003c/p\u003e\n \u003cp\u003eGuild 12. Ass. Cynodon dactylon\u0026thinsp;+\u0026thinsp;Echinochloa crusgalli\u0026thinsp;+\u0026thinsp;Cyperus rotundus, \u003cem\u003ehygrophyte and mesophyte community\u003c/em\u003e, flood-tolerant riparian herbs including 3 samples and 9 species. The companion species are Amaranthus retroflexus, Xanthium sibiricum and Torulinium ferax, which are mainly found at elevations of 145\u0026ndash;155 m.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec17\" class=\"Section2\"\u003e\n \u003ch2\u003e3.5 Response of plant communities in the TGR to water level changes and environmental factors\u003c/h2\u003e\n \u003cp\u003eAll soil chemistry properties were significant (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.05) across sites (Fig. \u003cspan class=\"InternalRef\"\u003e7\u003c/span\u003e). SM, OM, TN, TP, pH firstly decreased and then gradually increased with \u0026quot;V\u0026quot; type changes along the altitude gradient, of which the lowest in the TGR area at 155\u0026ndash;165 m altitude, and all changes were significant except for pH. The AP, NH\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e+\u003c/sup\u003e, NO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e-\u003c/sup\u003e in the TGR area had a significant decreasing trend with the increasing altitude.\u003c/p\u003e\n \u003cp\u003eLow altitude. 145\u0026ndash;155 m; Middle altitude. 155\u0026ndash;165 m; High altitude. 165\u0026ndash;175 m. Values are means\u0026thinsp;\u0026plusmn;\u0026thinsp;SE. SM, soil moisture; OM, organic matte; TN, total nitrogen; NO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e-\u003c/sup\u003e, nitrate; NH\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e+\u003c/sup\u003e, ammonium; TP, total phosphorus; AP, available phosphorus.\u003c/p\u003e\n \u003cp\u003eSoil environmental factors and hydrological factor in the WLFZ significantly influenced the distribution pattern of plant guilds (Fig. \u003cspan class=\"InternalRef\"\u003e8\u003c/span\u003e). The ranking of plant guilds in response to water level changes and environmental factors in the WLFZ of the TGR was shown in Table \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e, and the first four paradigmatic axes cumulatively explained 44.3% of the guild changes. The species-environment correlation coefficients for axes 1 and 2 were 0.8615 and 0.8777, respectively, and the sum of the eigenvalues of the first two axes accounted for 62.83% of the total eigenvalues, containing most of the ranking information, so the data from the first two axes were used to analyze the relationship between guilds and environmental factors. As can be seen from Tables \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e and \u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e and Fig. \u003cspan class=\"InternalRef\"\u003e8\u003c/span\u003e, the highest correlation between flooding time and elevation with axis 1 was \u0026minus;\u0026thinsp;0.8297 and 0.7943, respectively. The correlation between OM and TP with axis 2 was higher at 0.5119 and 0.4327, respectively. As seen by the CCA ordination diagram (Fig. \u003cspan class=\"InternalRef\"\u003e8\u003c/span\u003e.), the position of each guild in the ordination space can reflect the ecological characteristics of the guilds and their distribution patterns. With the increasing altitude, the distribution patterns of the plant guilds in the WLFZ were like this. The lower altitude area (145\u0026ndash;155 m) was dominated by annual plant guilds, i.e., \u003cem\u003eEchinochloa crusgalli and Amaranthus retroflexus\u003c/em\u003e. The middle part (156\u0026ndash;165 m) was dominated by annuals and perennial plant guilds, i.e., \u003cem\u003eCynodon dactylon, Cyperus rotundus, Bidens pilosa\u003c/em\u003e, \u003cem\u003eXanthium sibiricum and Melilotus officinalis\u003c/em\u003e. The top area (166\u0026ndash;175 m) was dominated by shrub and herb plant guilds, i.e., \u003cem\u003eEchinochloa crusgalli, Cynodon dactylon, Eriochloa villosa\u003c/em\u003e and\u0026nbsp;\u003cem\u003eAbutilon theophrasti\u003c/em\u003e.\u003c/p\u003e\n \u003cdiv class=\"gridtable\"\u003e\u0026nbsp;\u0026nbsp;\u003ctable id=\"Tab1\" border=\"1\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e\n \u003cdiv class=\"CaptionContent\"\u003e\n \u003cp\u003eCCA ranking axis eigenvalues and interpretation\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\u0026nbsp;\u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eAxis 1\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eAxis 2\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eAxis 3\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eAxis 4\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eEigenvalue\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.1168\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.0879\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.0692\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.0519\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eExplained changes (cumulative)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e12.38\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e21.69\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e29.02\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e34.52\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSpecies-environmental correlation\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.8615\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.8777\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.7971\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.8052\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eFitting variation in interpretation (cumulative)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e27.96\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e48.99\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e65.55\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e77.97\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n \u003c/div\u003e\n \u003cdiv class=\"gridtable\"\u003e\n \u003cdiv align=\"char\" class=\"colspec\"\u003e\u003cbr\u003e\u003c/div\u003e\u0026nbsp;\u0026nbsp;\u003ctable id=\"Tab2\" border=\"1\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e\n \u003cdiv class=\"CaptionContent\"\u003e\n \u003cp\u003eCorrelation of 10 soil chemistry properties with each CCA axis\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\u0026nbsp;\u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eAxis 1\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eAxis 2\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eAxis 3\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eAxis 4\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eElevation\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.7943\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.1183\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.0124\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.0287\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eFlooding duration\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e-0.8297\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.0702\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.0519\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e-0.0828\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSM\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e-0.0779\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.0455\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.2981\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e-0.7346\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eAP\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e-0.4317\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.2144\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.1826\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e-0.1407\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eNH\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e+\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e-0.3453\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e-0.2666\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.1734\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e-0.0061\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eNO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e\u0026minus;\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e-0.2049\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.2193\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.3508\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.0255\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eOM\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.2296\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.5119\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e-0.3025\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.0315\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003epH\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e-0.3274\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e-0.2285\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e-0.2558\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.2327\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eTN\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.2662\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e-0.0272\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.0923\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e-0.3163\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eTP\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.2579\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.4327\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.5212\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e-0.1251\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n \u003c/div\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec18\" class=\"Section2\"\u003e\n \u003ch2\u003e3.6 Niche breadth\u003c/h2\u003e\n \u003cp\u003eThe niche breadth of species in the WLFZ were listed in the Table \u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003e, the top 8 of which were \u003cem\u003eC. dactylon\u003c/em\u003e (21.918) \u0026gt;\u003cem\u003eX. sibiricum\u003c/em\u003e (13.275) \u0026gt;\u003cem\u003eB. pilosa\u003c/em\u003e (11.318) \u0026gt;\u003cem\u003eE. crusgalli\u003c/em\u003e (9.472) \u0026gt;\u003cem\u003eC. rotundus\u003c/em\u003e (6.407) \u0026gt;\u003cem\u003eEclipta prostrata\u003c/em\u003e (6.052) \u0026gt;\u003cem\u003eD. sanguinalis\u003c/em\u003e (5.967) \u0026gt;\u003cem\u003eS. viridis\u003c/em\u003e (5.816). And the niche breadth of \u003cem\u003eC. dactylon\u003c/em\u003e was significantly larger than that of others. Under different altitude sections, \u003cem\u003eC. dactylon\u003c/em\u003e (7.0836) \u0026gt;\u003cem\u003eE. crusgalli\u003c/em\u003e (3.3973) \u0026gt; \u003cem\u003eB. pilosa\u003c/em\u003e (3.1698) at the lower elevations (145\u0026ndash;155 m); \u003cem\u003eC. dactylon\u003c/em\u003e (8.176) \u0026gt;\u003cem\u003eX. sibiricum\u003c/em\u003e (4.436) \u0026gt;\u003cem\u003eE. crusgalli\u003c/em\u003e (3.721) at the middle elevations (155\u0026ndash;165 m); \u003cem\u003eC. dactylon\u003c/em\u003e (6.659) \u0026gt;\u003cem\u003eX. sibiricum\u003c/em\u003e (6.0956) \u0026gt; \u003cem\u003eE. prostrata\u003c/em\u003e (4.889) at the highest elevations (165\u0026ndash;175 m). The dominant species had the different niche breadth in different elevations. Of these, the niche breadth of \u003cem\u003eC. dactylon\u003c/em\u003e at the middle elevations (155\u0026ndash;165 m) was the highest (8.176) and lowest at the higher elevations (165\u0026ndash;175 m). And the niche breadth of\u0026nbsp;\u003cem\u003eC. dactylon\u003c/em\u003e was obvious higher than other species at the lower (145\u0026ndash;155 m) and the middle elevations (155\u0026ndash;165 m), but not at the highest elevations (165\u0026ndash;175 m). The niche breadth of most of perennial herbs were higher at the highest elevations (165\u0026ndash;175 m) than that at the lower (145\u0026ndash;155 m) and middle elevations (155\u0026ndash;165 m).\u003c/p\u003e\n \u003cdiv class=\"gridtable\"\u003e\u0026nbsp;\u0026nbsp;\u003ctable id=\"Tab3\" border=\"1\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e\n \u003cdiv class=\"CaptionContent\"\u003e\n \u003cp\u003eChanges of Importance values and niche breadth of dominant plants at different altitudes in the WLFZ\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\" rowspan=\"2\"\u003e\n \u003cp\u003eSpecies\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\" colspan=\"4\"\u003e\n \u003cp\u003eP\u003csub\u003ei\u003c/sub\u003e\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\" colspan=\"4\"\u003e\n \u003cp\u003eB\u003csub\u003ei\u003c/sub\u003e\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e145\u0026ndash;155 m\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e155\u0026ndash;165 m\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e165\u0026ndash;175 m\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eTotal\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e145\u0026ndash;155 m\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e155\u0026ndash;165 m\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e165\u0026ndash;175 m\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eTotal\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eCynodon dactylon\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e3.854\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e4.537\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e3.470\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e11.861\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e7.084\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e8.176\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e6.659\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e21.918\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eXanthium sibiricum\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.061\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.215\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.280\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e3.556\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e2.743\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e4.436\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e6.096\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e13.275\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eCyperus rotundus\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.444\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.085\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.567\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e3.097\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e2.505\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e2.886\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.016\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e6.407\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eEchinochloa crusgalli\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.956\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.183\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.787\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e2.926\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e3.397\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e3.721\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e2.353\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e9.472\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSetaria viridis\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.415\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.157\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.199\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e2.772\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.766\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.960\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e3.091\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e5.816\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eBidens pilosa\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.717\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.951\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.003\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e2.672\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e3.170\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e3.259\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e4.889\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e11.318\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eDigitaria sanguinalis\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.433\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.848\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.179\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e2.460\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.679\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e2.345\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e2.943\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e5.967\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003ePolygonum hydropiper\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.957\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.665\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.747\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e2.369\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.536\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.811\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e2.365\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e5.712\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eEclipta prostrata\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.454\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.592\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.809\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e1.856\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.901\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e2.188\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.963\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e6.052\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eAbutilon theophrasti\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.636\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.604\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.486\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e1.726\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.447\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e2.236\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.015\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e4.698\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eAlternanthera philoxeroides\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.671\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.300\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.689\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e1.659\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.154\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.766\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.183\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e2.103\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eBidens tripartita\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.621\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.453\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.581\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e1.655\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.216\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.314\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.417\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e2.947\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eAcalypha australis\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.445\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.494\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.438\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e1.377\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.893\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.936\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.153\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e2.981\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSolanum nigrum\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.243\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.555\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.473\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e1.271\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.885\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e2.271\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.707\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e3.863\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eEriochloa villosa\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.151\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.300\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.773\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e1.224\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.214\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.253\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.796\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e1.263\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eMelilotus officinalis\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.937\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.937\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.210\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e1.210\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eEleusine indica\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.249\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.234\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.325\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.808\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.394\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.222\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.479\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e1.096\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eCyperus difformis\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.270\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.176\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.221\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.667\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.353\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.067\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.620\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e1.039\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eHumulus scandens\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.129\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.231\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.190\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.550\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.175\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.326\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.425\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.926\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eArtemisia argyi\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.164\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.162\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.196\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.521\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.077\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.067\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.570\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.713\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eAgeratum conyzoides\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.033\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.189\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.259\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.482\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.077\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.079\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.369\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.525\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eEuphorbia humifusa\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.035\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.294\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.151\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.480\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.077\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.348\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.407\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.832\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eAeschynomene indica\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.160\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.178\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.134\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.472\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.083\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.382\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.198\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.664\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eConyza canadensis\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.057\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.402\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.459\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.123\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.444\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e1.566\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eAmaranthus retroflexus\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.133\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.055\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.269\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.457\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.244\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.067\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.715\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e1.026\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003ePhyllanthus urinaria\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.204\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.165\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.086\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.456\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.463\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.522\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.162\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e1.148\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eAmmannia baccifera\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.446\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.446\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.077\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.077\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eErigeron annuus\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.038\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.236\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.171\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.445\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.077\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.071\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.138\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.286\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSalvia plebeia\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.209\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.050\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.124\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.383\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.161\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.100\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.258\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.519\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003ePortulaca oleracea\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.252\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.073\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.325\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.440\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.122\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.562\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003ePouzolzia zeylanica\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.023\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.275\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.298\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.067\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.564\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.631\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eArtemisia carvifolia\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.112\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.182\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.295\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.148\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.430\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.579\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eAnemarrhena asphodeloides\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.067\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.197\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.265\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.071\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.452\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.524\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003ePhysalis alkekengi\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.042\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.147\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.063\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.252\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.067\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.208\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.125\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.400\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eVigna radiata\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.139\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.108\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.248\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.083\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.125\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.208\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eArachis hypogaea\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.211\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.211\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.091\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.091\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eAster tataricus\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.063\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.127\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.190\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.139\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.267\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.406\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eLindernia procumbens\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.169\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.169\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.056\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.056\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eChenopodium ambrosioides\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.116\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.045\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.161\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.215\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.071\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.286\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eMazus japonicus\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.161\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.161\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.071\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.071\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eAmbrosia artemisiifolia\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.061\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.095\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.156\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.204\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.333\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.537\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eAlopecurus aequalis\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.152\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.152\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.090\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.090\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSesbania cannabina\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.123\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.123\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.421\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.421\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eHemistepta lyrata\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.107\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.107\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.167\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.167\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eVetiveria zizanioides\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.107\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.107\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.368\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.368\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eLindernia crustacea\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.054\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.045\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.099\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.077\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.167\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.244\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eBupleurum longiradiatum\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.091\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.091\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.067\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.067\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eDactyloctenium aegyptium\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.087\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.087\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.271\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.271\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eJuncus effusus\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.083\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.083\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.091\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.091\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003ePhyla nodiflora\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.082\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.082\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.091\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.091\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eCelosia argentea\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.080\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.080\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.196\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.196\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSorghum bicolor\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.072\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.072\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.139\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.139\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eDaucus carota\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.072\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.072\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.416\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.416\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eLeptochloa chinensis\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.071\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.071\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.318\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.318\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003ePilea cavaleriei\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.067\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.067\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.071\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.071\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eCosmos bipinnata\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.063\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.063\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.056\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.056\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eMosla scabra\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.058\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.058\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.167\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.167\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eTorulinium ferax\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.057\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.057\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.077\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.077\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eArtemisia capillaris\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.056\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.056\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.067\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.067\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSida acuta\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.050\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.050\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.083\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.083\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eEuphorbia hypericifolia\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.049\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.049\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.103\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.103\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eArthraxon hispidus\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.042\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.042\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.125\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.125\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eTrigonotis peduncularis\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.036\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.036\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.071\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.071\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eMimosa pudica\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.035\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.035\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.071\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.071\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eRorippa indica\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.033\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.033\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.077\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.077\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eLeucaena leucocephala\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.029\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.029\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.077\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.077\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eCommelina communis\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.028\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.028\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.067\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.067\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eVicia sepium\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.025\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.025\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.071\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.071\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eMedicago sativa\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.023\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.023\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.071\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.071\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eCorydalis pallida\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.017\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.017\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.077\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.077\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eEuphorbia helioscopia\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.014\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.014\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.067\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.067\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eCucumis sativus\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.011\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.011\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.056\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.056\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eErigeron acer\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.007\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.007\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.056\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.056\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n \u003c/div\u003e\n \u003cp\u003e\u0026ldquo;-\u0026rdquo;. Species was disappeared; P\u003csub\u003ei\u003c/sub\u003e. Importance value; B\u003csub\u003ei\u003c/sub\u003e. Niche breadth.\u003c/p\u003e\n \u003cp\u003eIt could be seen from the correlation between niche breadths and important values of each elevation in the surveyed sample plot under three types of elevations were positively correlated (Fig. \u003cspan class=\"InternalRef\"\u003e9\u003c/span\u003e). There was also a significant positive correlation between the niche breadths and the important values of each species, and the explanatory variables were high. The dominant species with high important value always had the higher niche breadths value. \u003cem\u003eC. dactylon\u003c/em\u003e both had the highest niche breadths and important values.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec19\" class=\"Section2\"\u003e\n \u003ch2\u003e3.7 Niche overlap\u003c/h2\u003e\n \u003cp\u003eNiche overlap by species for each altitude section was calculated (Fig. \u003cspan class=\"InternalRef\"\u003e10\u003c/span\u003e.). There were 703 niche overlap indexes calculated by 38 species at the altitude of 145\u0026ndash;155 m, 33.85% of which were 0, 35.85% of which were greater than 0.5 and 38.55% of which were less than 0.2. \u003cem\u003eC. dactylon\u003c/em\u003e, \u003cem\u003eX. sibiricum\u003c/em\u003e, \u003cem\u003eS. viridis\u003c/em\u003e, and \u003cem\u003eD. sanguinalis\u003c/em\u003e all had the high niche overlap value compared with most of species. However, there were also some species with low niche breadths and important value, such as \u003cem\u003eH. scandens\u003c/em\u003e, \u003cem\u003eL. crustacea\u003c/em\u003e and \u003cem\u003eC. ambrosioides\u003c/em\u003e, which had high niche overlap values.\u003c/p\u003e\n \u003cp\u003eThere were 901 niches overlap indexes calculated by 43 species at the altitude of 155\u0026ndash;165 m, 44.73% of which were 0, 18.09% of which were greater than 0.5 and 49.28% of which were less than 0.2. \u003cem\u003eC. dactylon\u003c/em\u003e, \u003cem\u003eX. sibiricum\u003c/em\u003e, \u003cem\u003eS. viridis\u003c/em\u003e, and \u003cem\u003eD. sanguinalis\u003c/em\u003e all had the high niche overlap value with most of species.\u003c/p\u003e\n \u003cp\u003eThere were 1596 niches overlap indexes calculated by 57 species at the altitude of 165\u0026ndash;175 m, 42.42% of which were 0, 20.86% of which were greater than 0.5 and 48.81% of which were less than 0.2. \u003cem\u003eC. dactylon\u003c/em\u003e, \u003cem\u003eC. rotundus\u003c/em\u003e, \u003cem\u003eX. sibiricum\u003c/em\u003e, \u003cem\u003eP. hydropiper\u003c/em\u003e, and \u003cem\u003eE. crusgalli\u003c/em\u003e all had the high niche overlap value with most of species. Niche overlap index of the same species in different altitudes was different. The niche overlap values of \u003cem\u003eC. dactylon\u003c/em\u003e were higher at the middle elevations (155\u0026ndash;165 m) than that at the higher (165\u0026ndash;175 m) and lower elevations (145\u0026ndash;155 m).\u003c/p\u003e\n\u003c/div\u003e"},{"header":"4. Discussion","content":" \u003cdiv id=\"Sec21\" class=\"Section2\"\u003e \u003ch2\u003e4.1. Anti-seasonal flooding substantially reduced species diversity in the WLFZ of the TGR\u003c/h2\u003e \u003cp\u003eA unique riparian ecosystem has been created as a result of anti-seasonal and continuous flooding after TGR operations, which notably influences the species diversity distribution patterns of plant communities and their functional characteristics (Li et al., 2022). Before the impoundment of the TGR, there were 405 vascular plants in the riparian area of the TGR (Wang et al., 2002). However, in the early stage of the TGR impoundment in 2009, only a total of 231 species, belonging to 61 families and 169 genera, was found in the WLFZ of the TGR (Liu et al., 2011). After the early 7 years of the TGR impoundment in 2010, Zhang et al., (2013) found that a few shrubs (\u003cem\u003eBoehmeria nivea, Lespedeza davidii, Lespedeza cuneata\u003c/em\u003e) and trees (\u003cem\u003eMorus alba, Albizia kalkora\u003c/em\u003e and \u003cem\u003eBroussonetia papyrifera\u003c/em\u003e) only appeared at the altitude of 170 m. The main vegetation type was herbs in the WLFZ. In the present study, after the early 19 years of the TGR impoundment, a total of 73 vascular plant species were identified in the WLFZ. Annual herbs accounted for the highest percentage of all life forms at each altitude. Annuals, perennials and shrubs accounted for 71.23%, 27.39% and 1.37% of the total number of species, respectively. Thus it could be seen, anti-seational and continuous flooding triggered the dramatic alterations in floristic composition, structure, and distribution pattern of plant communities in the riparian zone.\u003c/p\u003e \u003cp\u003eAt the same time, after 19 years of water storage, plant life forms have been altered dramatically in the new riparian forest. This novel anti-seasonal flooding reduced functional diversity, mostly owing to the loss of stress-tolerant woody species and competitive perennial herbs. Essentially new hydromorphological conditions following damming limited recruitment of native shrub and tree species guilds sensitive to floods (to drag forces, inundation, and anoxia). \u003cspan type=\"Underline\" class=\"Underline\" name=\"Emphasis\"\u003eThus it can be seen\u003c/span\u003e that woody plants (trees and shrubs) showed the greatest decrease, and the proportion of perennial herbs also decreased, while the proportion of annual herbs increased significantly, indicating that herbs, especially annual herbs, i.e. Compositae, Gramineae and Leguminosae families, are more suitable for the environment of water level fluctuations in the TGR. Thus it could be seen, the pre-dam vegetation failed to persist under the new riparian ecosystem, and the species richness and diversity of the riparian forests were significantly lower due to the great hydrological shifts by the TGD construction (New \u0026amp; Xie, 2008; Chen et al., 2012; Chen et al., 2022).\u003c/p\u003e \u003cp\u003eA plausible reason was that most annuals, i.e., Compositae, Gramineae and Leguminosae, germinate in spring and fructify in autumn during the low water level of the TGR operation within a growth season, and have the flooding tolerance and the capacity to synchronize germination and growth within a short-exposure period, which underlie the plant species alterations. Therefore, these adaptive annuals survive as dominant species in the WLFZ of the TGR mainly because their phenology do not compound with the submergence occurring time. The recession of the water level left a nearly barren drawdown zone and provided an entire growing season for the forbs and graminoids, especially for the annual and biennial and perennial species. With its short life cycle, annual herbs were able to go from seed to seed life cycle in a relatively short period of time after water receding and before water storage. The next year, a new life cycle began with the emergence of seeds from nearby seed sources or soil seed banks (De Souza et al., 2021). After receding, clonal growth can quickly expand space and gain an advantage in the inter-specific competition by their extensive lateral spread and forming dense, nearly monospecific stands, i.e., \u003cem\u003eC. dactylon\u003c/em\u003e, which can quickly re-sprout following continuous inundation and take advantage of the short-exposure period before the reservoir is filled again. Thus, the proportion of annual herbaceous species showed a decreasing trend while the proportion of perennial herbaceous species showed an increasing trend along elevation gradients. The transformed species richness of forbs, graminoids, annuals, biennials and perennials increased significantly, especially the Compositae, Graminaceae and Leguminaceae plants.\u003c/p\u003e \u003cp\u003eSpecies diversity distribution along elevation gradients has different patterns. Some studies have demonstrated that species richness patterns from the lowest to highest elevations may show a monotonic decrease, or a monotonic increase; others have revealed hump-shaped patterns with a peak in richness at mid-elevations (Mallen-cooper \u0026amp; Pickering, 2008; Trigas et al., 2013; Arturo \u0026amp; Lauro, 2005). In the present study, the S, H and D increased with the increasing elevation but E showed a contrary trend (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e). This species distribution pattern might be caused by several synergetic attributes (e.g., the submergence depth, the tolerant capacity to flooding, the life form, the dispersal mode, and the inter-specific competition) (Zhang et al., 2013). The lower elevation area (145\u0026ndash;155 m) is generally prone to more severe flooding with a greatest depth of inundation (30 m) and prolonged inundation duration (nearly half 6 months), which resulted in the lower S, and H than the higher elevation area (156\u0026ndash;165 m and 165\u0026ndash;175 m). Thus, these annual species in the low elevation area may rapidly attain maturity before being submerged with short life cycle (Zhang et al., 2013). At the highest elevations (166\u0026ndash;175 m), seed dispersal by wind, water, animals, and humans might be important factors resulting in the higher diversity index (Merritt \u0026amp; Wohl, 2006). However, H showed hump-shaped patterns with a peak at mid-reaches from upstream to downstream (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e). The middle reaches of the reservoir area were mostly forested on both sides of the Yangtze River, with less agricultural cultivation and less human influence. In the downstream reaches, the Citrus farming industry on both sides of the Xiangxi and Tongzhuang rivers was booming, and the plant communities on both sides of the river was more affected by agricultural farming and human interference. Ecological characteristics of plant guilds as an assemblage of plant population are response to the environment changes and are more pronounced during succession (Yang et al., 2012; Ge et al., 2020). In this study, it was found that the main influence factors affecting the spatial distribution of the plant guilds in the new riparian forest were hydrological factors, such as elevation (different flooding depths) and flooding time. So, the pattern of the plant guilds in the TGR was mainly affected by water level disturbance. This result was largely consistent with other results that hydrological conditions determined the vegetation diversity and aboveground biomass patterns at the elevation gradients of the drawdown zone (Wang et al., 2014). It can be seen that the vegetation spatial distribution of the TGR area was heavily influenced by the hydrological factors, i.e., different flooding depth and flooding time in the reservoir area and the species diversity was significantly reduced.\u003c/p\u003e \u003cp\u003eSoil nutrient concentrations could also strongly affect plant species diversity and evenness (Aerts, et al., 2003). In the present study, the concentrations of TN and TP appeared to be higher at the elevations of 165\u0026ndash;175 m than at the elevations of 145\u0026ndash;155 m and 155\u0026ndash;165 m. The continuous submergence in winter and the high frequency of floods in summer may result in this pattern for soil nutrients may be released when submerged and soil that serves as a nutrient source may be scoured by repeated flooding. Qui \u0026amp; McComb (1996) also reported that the concentration of TN was reduced after continuous submergence. And Roem \u0026amp; Berendse (2000) studied nutrient supply ratio as possible factors determining changes in plant species diversity in grassland and heathland communities, which showed that plant species with high diversity were at balanced N/P ratios between 10 and 14. However, in the present study, N/P ratios of the soil was between 0.98 and 1.56 with an average of 1.26, which showed that N was a limiting factor in the soil in the new riparian forest. The increase of N supply in a N-limited grassland (e.g., N/P ratio\u0026thinsp;\u0026lt;\u0026thinsp;10) may lead to an increase in biodiversity (Roem \u0026amp; Berendse, 2000). In this study, the distribution patterns of plant guilds were positively associated with TN, TP, and OM, while negatively correlated with pH, NH\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e+\u003c/sup\u003e-N, NO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e\u0026minus;\u003c/sup\u003e-N, and AP in the CCA (Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003eb.). Of these, the significantly negative correlation between NO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e\u0026minus;\u003c/sup\u003e-N and the distribution patterns of plant species (\u003cem\u003ep\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.05) was consistent with the results that excess of NO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e\u0026minus;\u003c/sup\u003e-N is known for its negative effect on the diversity of plant guilds (Aerts, et al., 2003). Therefore, N might be a soil nutrient limiting factor in determining the alterations in plant species diversity and plant distribution patterns in addition to elevation gradients and flooding time in the new riparian forest of the TGR.\u003c/p\u003e \u003cp\u003eThe results also corroborated the trend of the species diversity index increasing with the elevation gradients. At higher elevations, the number of plant species is increasing and the competition between species becoming more intense. From bottom to top along axis 2, OM and TP rose (Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003eb.). This result was basically the same as the pattern shown in Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e, which showed that the influence of elevation and flooding on the distribution pattern of the plant guilds in the TGR was more obvious than that of OM and TP, and the first order axis could explain the interrelationship between the plant guild and the habitat in the declining zone (Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003ec.). That is, although the spatial distribution of the plant guilds in the subduction zone of the TGR area was the result of a combination of multiple factors, the influence of elevation gradients and flooding time played a dominant role in the formation of the spatial pattern of the plant guilds in the new riparian forest of the TGR and the second factors were TN, TP, and OM.\u003c/p\u003e \u003cp\u003eIn the TGR area, the plant guilds were distributed from left to right along the elevation and flooding time, as follows Ass. \u003cem\u003eC. dactylon\u003c/em\u003e\u0026thinsp;+\u0026thinsp;\u003cem\u003eE. crusgalli\u003c/em\u003e\u0026thinsp;+\u0026thinsp;\u003cem\u003eC. rotundus\u003c/em\u003e; Ass. C. \u003cem\u003edactylon\u003c/em\u003e\u0026thinsp;+\u0026thinsp;\u003cem\u003eA. theophrasti\u003c/em\u003e\u0026thinsp;+\u0026thinsp;\u003cem\u003eS. plebeia\u003c/em\u003e; Ass. \u003cem\u003eE. crusgalli\u003c/em\u003e\u0026thinsp;+\u0026thinsp;\u003cem\u003eD. sanguinalis\u003c/em\u003e\u0026thinsp;+\u0026thinsp;\u003cem\u003eS. viridis\u003c/em\u003e; Ass. \u003cem\u003eC. dactylon\u003c/em\u003e; Ass. \u003cem\u003eB. pilosa\u003c/em\u003e; Ass. \u003cem\u003eB. tripartita\u003c/em\u003e; Ass. \u003cem\u003eD. sanguinalis\u003c/em\u003e; Ass. \u003cem\u003eH. scandens\u003c/em\u003e; Ass. \u003cem\u003eS. viridis\u003c/em\u003e; Ass. \u003cem\u003eC. canadensis\u003c/em\u003e\u0026thinsp;+\u0026thinsp;\u003cem\u003eB. pilosa\u003c/em\u003e; Ass. \u003cem\u003eE. prostrata\u003c/em\u003e\u0026thinsp;+\u0026thinsp;\u003cem\u003eC. dactylon\u003c/em\u003e; Ass. \u003cem\u003eC. dactylon\u003c/em\u003e\u0026thinsp;+\u0026thinsp;\u003cem\u003eM. officinalis\u003c/em\u003e (Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003ea.). There were some overlaps between the types. Ass. \u003cem\u003eC. dactylon\u003c/em\u003e\u0026thinsp;+\u0026thinsp;\u003cem\u003eE. crusgalli\u003c/em\u003e\u0026thinsp;+\u0026thinsp;\u003cem\u003eC. rotundus\u003c/em\u003e and Ass. C. \u003cem\u003edactylon\u003c/em\u003e\u0026thinsp;+\u0026thinsp;\u003cem\u003eA. theophrasti\u003c/em\u003e\u0026thinsp;+\u0026thinsp;\u003cem\u003eS. plebeia\u003c/em\u003e located at the altitude gradient of 145\u0026ndash;155 m, with long flooding durations and short growth durations. The medium elevation gradient (155\u0026ndash;165 m) was for the Ass. \u003cem\u003eE. crusgalli\u003c/em\u003e\u0026thinsp;+\u0026thinsp;\u003cem\u003eD. sanguinalis\u003c/em\u003e\u0026thinsp;+\u0026thinsp;\u003cem\u003eS. viridis\u003c/em\u003e and Ass. \u003cem\u003eC. dactylon\u003c/em\u003e. Ass.\u003cem\u003eB. pilosa\u003c/em\u003e, Ass. \u003cem\u003eB. tripartita\u003c/em\u003e, Ass. \u003cem\u003eD. sanguinalis\u003c/em\u003e, Ass. \u003cem\u003eH. scandens\u003c/em\u003e, Ass. \u003cem\u003eS. viridis\u003c/em\u003e, Ass. \u003cem\u003eC. canadensis\u003c/em\u003e\u0026thinsp;+\u0026thinsp;\u003cem\u003eB. pilosa\u003c/em\u003e, Ass. \u003cem\u003eE. prostrata\u003c/em\u003e\u0026thinsp;+\u0026thinsp;\u003cem\u003eC. dactylon\u003c/em\u003e and Ass. \u003cem\u003eC. dactylon\u003c/em\u003e\u0026thinsp;+\u0026thinsp;\u003cem\u003eM. officinalis\u003c/em\u003e were distributed at high altitudes (165\u0026ndash;175 m) in the WLFZs, with less or almost unaffected by flooding. In the early stages of flooding in 2010, there were 18 main plant guilds in the WLFZ of the TGR, including 5 xerophyte, 6 hygrophyte and 7 mesophyte guilds (Chen et al., 2012). In the present study, after 19 times of water level fluctuations in the TGR, the 12 main plant guild types were discovered, belonging to hygrophyte and mesophyte communities. Xerophyte guilds almost disappeared. Thus, the taxonomic and functional characteristics of communities were differently as they may respond to important drivers differently. The vegetation composition of the WLFZs in the TGR showed a \u003cb\u003es\u003c/b\u003eignificant change with a transition from xerophytes to hygrophytes and mesophytes with the increasing flooding time. The observed riparian plant guild response patterns to prolonged submergence in the WLFZs of Yangtze River might hopefully be transferred to similiar rivers with little or no existing information in other regions regardless of whether or not they share species. The guild approach helps develop general frameworks to predict vegetation responses to changing environmental conditions.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec22\" class=\"Section2\"\u003e \u003ch2\u003e4.2. Niche structure and utilization of limited resources\u003c/h2\u003e \u003cp\u003eNiche breadth describes a suite of environments or resources, in the broadest sense, which a species can inhabit or use, which measures the range of resource characteristics across which a species exists, and indicates the extent that a species utilizes different types of resources (Slatyer et al., 2013), while niche overlap refers to the partial or complete sharing of resources or other ecological factors (predators, foraging space, soil type, and so on) by two or more species (Colwell \u0026amp; Futuyma, 1971). The measures of niche breadth and overlap are all based on the distribution of individual organisms, by species, within a set of resource states (Colwell \u0026amp; Futuyma, 1971). In the present study, the dominant species were \u003cem\u003eC. dactylon\u003c/em\u003e, \u003cem\u003eX. sibiricum\u003c/em\u003e, \u003cem\u003eC. rotundus\u003c/em\u003e, \u003cem\u003eE. crusgalli\u003c/em\u003e, \u003cem\u003eS. viridis\u003c/em\u003e, \u003cem\u003eB. pilosa\u003c/em\u003e, \u003cem\u003eD. sanguinalis\u003c/em\u003e and \u003cem\u003eP. hydropiper\u003c/em\u003e in the riparian forest of the TGR according to the importance value and niche breadth. The correlations between niche breadths and important values of each elevation were positively correlated in the surveyed sample plots under three types of elevations (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e.). Under different altitude sections according to niche breadth, \u003cem\u003eC. dactylon\u003c/em\u003e (7.0836) \u0026gt;\u003cem\u003eE. crusgalli\u003c/em\u003e (3.3973) \u0026gt;\u003cem\u003eB. pilosa\u003c/em\u003e (3.1698) at the lower elevations (145\u0026ndash;155 m); \u003cem\u003eC. dactylon\u003c/em\u003e (8.176) \u0026gt;\u003cem\u003eX. sibiricum\u003c/em\u003e (4.436) \u0026gt;\u003cem\u003eE. crusgalli\u003c/em\u003e (3.721) at the middle elevations (155\u0026ndash;165 m); \u003cem\u003eC. dactylon\u003c/em\u003e (6.659) \u0026gt;\u003cem\u003eX. sibiricum\u003c/em\u003e (6.0956) \u0026gt;\u003cem\u003eE. prostrata\u003c/em\u003e (4.889) at the highest elevations (165\u0026ndash;175 m). \u003cem\u003eC. dactylon\u003c/em\u003e was the most dominant species in the novel riparian forest with highest importance value and niche breadth at each altitude. \u003cem\u003eC. dactylon\u003c/em\u003e might have evolved morphological, physiological, and biochemical adaptations to oxygen deficiency, such as dormant tubers or rhizomes (Zhang et al., 2013). So, it could germinate quickly after submerged period to against the coming dry period to achieve the greatest competitive advantages in the WLFZ. There were the most of species pairs with the niche overlap index less than 0.2 or 0 at the middle altitude (155\u0026ndash;165 m). The vegetation in the middle altitude (155\u0026ndash;165 m) were the least affected by the Yangtze River flooding during the dry period. \u003cem\u003eC. dactylon\u003c/em\u003e almost formed a single-species community at the middle altitude (155\u0026ndash;165 m), because of its strong acclimation and fast growth as well as facile vegetative propagation compared with other species.\u003c/p\u003e \u003cp\u003eNiche breadth in the study area had high niche overlap between species, but in some habitat conditions, the species with narrower niche breadth appeared larger niche overlap. There were some plants, such as \u003cem\u003eH. scandens\u003c/em\u003e, \u003cem\u003eL. crustacea\u003c/em\u003e and \u003cem\u003eC. ambrosioides\u003c/em\u003e, niche overlap value was 1.00, almost perfect overlap. Most of these species had lower niche overlap with those dominant species. In fact, the niche occupation of resource space between two species was only infinitely close, so the overlap was only infinitely close to 1.00. This indicated that there was no direct linear relationship between niche breadth and niche overlap, which was caused by the heterogeneity of spatial distribution of environmental resources available to species (Chen et al., 2019). The \u003cem\u003eTAO\u003c/em\u003e\u003csub\u003e\u003cem\u003eih\u003c/em\u003e\u003c/sub\u003e in the different altitude area was highest at the altitude of 145\u0026ndash;155 m (0.3642), lower at 165\u0026ndash;175 m (0. 2619) and 155\u0026ndash;165 m (0.2524) in descending order. The vegetation in the lower elevations (145\u0026ndash;155 m) suffered the longest periods of winter flooding and summer flood. So they had the shortest time to complete their life cycle under the influence of both winter storage and summer flood. The results showed that anti-seasonal and continuous flooding would lead to the gradual disappearance of the original diverse niches, resulting in more uniform habitats, and more obvious competition among species with similar resource requirements. The comprehensive ecological level analysis concluded that, after 19-year inundation of the TGR, the vegetation of the new riparian forest was still in the high niche overlap, intense competition, and species specialization, which showed that the vegetation was still in the early stage of primary succession, ecosystem stability was poor, and habitat fragmentation was severe in the TGR area.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec23\" class=\"Section2\"\u003e \u003ch2\u003e4.3. Practical implications for vegetation restoration and reconstruction\u003c/h2\u003e \u003cp\u003eThe anti-seasonal and continuous flooding precipitated loss of the original vegetation, especially trees and shrubs after the filling of the TGR. We found a significant decrease in the number of vascular plants compared to the pre-flooding period. The proportion of annual herbs, especially Compositae, Gramineae and Leguminosae plants have significantly increased in the riparian forest as a result of their adaptation strategies. And we found some invasive plants such as \u003cem\u003eE. annuus\u003c/em\u003e began to show dominance in the vegetation composition of the new riparian forest in the TGR. The TGR area is not only one of the most biodiverse areas in China, but also one of the most endemic species areas in the world (Jin et al., 1984). The dominance of invasive plants can cause great harm to the gene pool and genetic diversity in the TGR area (Yang et al., 2012; Ge et al., 2020). The present results showed the high heterogeneity of species diversity and environmental factors in the TGR areas with significant habitat changes and poor ecosystem stability. Therefore, there may be some differences in the governance strategies adopted in different areas of the novel riparian ecosystem for vegetation restoration of the riparian forests.\u003c/p\u003e \u003cp\u003eAccording to the comparative analysis of the vegetation status in the TGR area, the following four implications are proposed:\u003c/p\u003e \u003cp\u003e(\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e) more attentions should be given to the indigenous species in the selection of species for the restoration and reconstruction of the novel riparian forests. The exploration and study of indigenous species in the reservoir may be a more effective and safe means of artificial vegetation restoration. Therefore, the above- described indigenous plant guilds should be prioritized in vegetation restoration efforts;\u003c/p\u003e \u003cp\u003e(\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e) differences between regions should be taken into account in the implement of vegetation restoration measures in the reservoir area. The construction of artificial guilds during vegetation restoration should be tailored to the local context and plant adaptations to local conditions;\u003c/p\u003e \u003cp\u003e(\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e) in general, when the artificial guilds are restored in the reservoir area, it may have a better effect with herbaceous plants as the main part, supplemented by shrubs or small trees in the middle-high elevation areas such as \u003cem\u003eDistylium chinense\u003c/em\u003e (Sun et al., 2020) and \u003cem\u003eTaxodium distichum\u003c/em\u003e (Li et al., 2010);\u003c/p\u003e \u003cp\u003e(\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e) studies have shown that stabilization of vegetation in the depression zone may take 70 years or more (Nilsson \u0026amp; Arad\u0026oacute;ttir, 2013; Nilsson et al., 2013; Nilsson et al., 1997; Nilsson et al., 2015). Although it has been 19 years since the formation of the WFLZ of the TGR, the niche differentiation between different dominant plants was lower, the inter-specific competition was more intense and the stability of plant guilds was still worse. Therefore, long term investigations and observations should be continued in this area to identify and monitor alterations in the characteristics of the plant guilds and soil properties due to anti-seasonal and continuous inundation on riparian areas triggered by flow regulation or global warmer climates.\u003c/p\u003e \u003c/div\u003e"},{"header":"5. Conclusions","content":"\u003cp\u003eIn the present study a total of 73 vascular plants were identified in the WLFZ. There were significant differences in the species number and species diversity index in the different elevation areas. These diversity indexes increased along elevation gradients. The dominant species of plants varied with elevation, but\u003cstrong\u003e\u003cem\u003e\u0026nbsp;\u003c/em\u003e\u003c/strong\u003e\u003cem\u003eC. dactylon\u003c/em\u003e always be the most dominant. And high niche breadth had a high niche overlap between species. Therefore, anti-seasonal water level rhythms precipitate substantial reduction of\u0026nbsp;plant\u0026nbsp;diversity,\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003especies competition and exclusion among species by expanding the niche in the guilds. Thus, the vegetation in the unique riparian ecosystems still was in the primary stage of plant community succession with low species diversity, high niche overlap, intense competition, and obvious single-species dominant communities. In addition, the spatial distribution of the plant guilds and niche characteristics were mainly influenced by the hydrological alterations (different flooding depths and flooding time) and the second factors were TN, TP, and OM. Annual herbs are better adapted to the fragmentation of the RWLFZ than perennial herbs, so it is suggested that the general policy of restoring and constructing artificial communities in the reservoir area should be mainly herbaceous, supplemented by shrubs or small trees. In order to establish a complete reference system for vegetation restoration, natural vegetation monitory plots in the different succession stages should be established in the different water level fluctuation zones of the TGR, and their environmental conditions, community structures and inter-specific relationships analyzed.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAuthors\u0026rsquo; contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eXiaoling Li,Xiaodie Duan\u0026nbsp;and\u0026nbsp;Wenxiong Yi:Writing-original draft.\u0026nbsp;Wenxiong Yi\u0026nbsp;and\u0026nbsp;Xiaodie Duan:Conceptualization;Data curation;Formal analysis.Gong Chen,\u003c/p\u003e\n\u003cp\u003eJin Yang and Danli Deng:Investigation; Methodology; Software. Xiaojuan Guo and Zhengjian Yang:Project \u0026nbsp;ministration;Resources;Fundingacquisition;\u003c/p\u003e\n\u003cp\u003eSupervision. Guiyun Huang, Meixiang Hu, Chen Ye:the writing-reviewing and editing.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eData availability\u003c/strong\u003e\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThe authors confirm that the data supporting the findings of this study are available within the article. Raw data that support the findings of this study area available from the corresponding author upon responsible request.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThis work was supported by the National Natural Science Foundation of China (No. 51779127), partially funded by the Youth Innovation Promotion Association of the Chinese Academy of Sciences (No.2019334) and Research Project on Seed Preservation Technology and Facilities of Rare Plants in the Three Gorges Reservoir Area--Investigation and Collection of Flooding-Tolerant germplasm resources (SDHZ2021346).\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgements\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eWe thank Jitan Liu, Wenqiang Wang, Wei Shi, Lei Sun, Ling Xiang, for their assistance during fieldwork.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eEthics approval and consent to participate\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis study did not involve any animal or human testing.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConflict of interest\u003c/strong\u003e\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThe authors declare that they have no competing interests.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent for publication\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eAerts R, De Caluwe H, Beltman B. 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Global Ecology and Conservation. 2020;21:e00866. https.//doi.org/10.1016/j.gecco.2019.e00866\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Anti-seasonal flooding, Species diversity pattern, Niche characteristics, Plant guilds, Riparian ecosystems, Three Gorges Reservoir","lastPublishedDoi":"10.21203/rs.3.rs-4053112/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-4053112/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eHuman-induced disturbances such as dam construction and regulation often alter the duration，frequency and seasonality of flooding and thus substantially influence plant characteristics in the hydro-fluctuation zones. However, the effect mechanism of anti-seasonal hydrological alterations on vegetation distribution patterns and niche characteristics in the water level fluctuation zones (WLFZs).is still unclear. In this study, 368 quadrats were selected to investigate the effects of the anti-seasonal hydrological regimes on the foristic composition, species diversity and niche characteristic in the hydro-fluctuation zone of the Three Gorges Reservoir (TGR), a unique riparian ecosystem, China. The results showed that the number of species per square meter (S), the Shannon-Wiener diversity index (H) and Simpson dominance index (D) of the plant guilds in the TGR increased significantly with elevation, which was inconsistent with humped diversity–disturbance relationship of the intermediate disturbance hypothesis, while the opposite trend was observed for the Pielou evenness index (E). The H, D, S and E from upstream to downstream firstly showed a significant increasing trend (\u003cem\u003ep\u003c/em\u003e\u0026lt;0.05), reached the highest in the middle reaches, and then decreased in the lower reaches. The vegetation was classified into 12 guild types but the vegetation composition showed a significant variation with a transition from xerophytes to mesophytes and hygrophytes with the increasing flooding time. \u003cem\u003eCynodon dactylon\u003c/em\u003e was the most dominant species based on its highest important value and niche breadth. And high niche breadth had a high niche overlap between species. Therefore, anti-seasonal hydrological alterations precipitated substantial reduction of plant diversity, species competition and exclusion among species by expanding the niche in the guilds. The vegetation in the unique riparian ecosystems was still in the primary stage of plant community succession with low species diversity, high niche overlap, intense competition and obvious single-species dominant communities. Compared to total nitrogen, total phosphorus and soil organic matter factors, the hydrological alteration filtering was more important in explaining the plant guild patterns and niche characteristics. Therefore, there may be some differences in the governance strategies adopted in different areas of the novel riparian ecosystems for vegetation restoration efforts of the riparian forests.\u003c/p\u003e","manuscriptTitle":"Anti-seasonal flooding drive substantial alterations in riparian plant diversity and niche characteristics in a unique hydro-fluctuation zone","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-03-22 18:53:05","doi":"10.21203/rs.3.rs-4053112/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"3e0b9fcf-6546-4a86-bffa-6fd5c7b12fdf","owner":[],"postedDate":"March 22nd, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2024-03-22T18:53:07+00:00","versionOfRecord":[],"versionCreatedAt":"2024-03-22 18:53:05","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-4053112","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-4053112","identity":"rs-4053112","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}