Responses of biomass and non-structural carbohydrates to soil moisture gradient of two Carex species in alpine meadow in Southeast Qinghai-Xizang Plateau

Responses of biomass and non-structural carbohydrates to soil moisture gradient of two Carex species in alpine meadow in Southeast Qinghai-Xizang Plateau | Authorea try { document.documentElement.classList.add('js'); } catch (e) { } var _gaq = _gaq || []; _gaq.push(['_setAccount', 'G-8VDV14Y67G']); _gaq.push(['_trackPageview']); (function() { var ga = document.createElement('script'); ga.type = 'text/javascript'; ga.async = true; ga.src = ('https:' == document.location.protocol ? 'https://ssl' : 'http://www') + '.google-analytics.com/ga.js'; var s = document.getElementsByTagName('script')[0]; s.parentNode.insertBefore(ga, s); })(); Skip to main content Preprints Collections Wiley Open Research IET Open Research Ecological Society of Japan All Collections About About Authorea FAQs Contact Us Quick Search anywhere Search for preprint articles, keywords, etc. Search Search ADVANCED SEARCH SCROLL This is a preprint and has not been peer reviewed. Data may be preliminary. 9 January 2025 V1 Latest version Share on Responses of biomass and non-structural carbohydrates to soil moisture gradient of two Carex species in alpine meadow in Southeast Qinghai-Xizang Plateau Authors : Zhongkui Li 0009-0006-1355-7811 and Dacai Zhang [email protected] Authors Info & Affiliations https://doi.org/10.22541/au.173640387.74289933/v1 Published BMC Plant Biology Version of record Peer review timeline 210 views 200 downloads Contents Abstract Information & Authors Metrics & Citations View Options References Figures Tables Media Share Abstract Soil moisture changes affect the dynamics of plant biomass and non-structural carbohydrates (NSC), and different species have different response strategies. In the alpine meadow of Dongda Mountain in Southeast Qinghai-Xizang Plateau, 5 quadrats were set up respectively along the soil moisture gradient and experimental materials were collected by total harvest method. The NSC concentration was determined by modified phenol concentrated sulfuric acid method. The relationships between the biomass, NSC and soil moisture content of two Carex species were analyzed by One-way ANOVA, Two-way ANOVA, principal component analysis and polynomial fitting. The results showed that the root biomass of C. alatauensis , stem biomass of C. parvula and leaf, above-ground, below-ground and total biomass of two species were significantly positively correlated with soil moisture content (R 2 = 0.17-0.68, P < 0.05). The NSC, soluble sugar (SS) and starch (ST) concentrations in roots and whole plant of C. parvula all increased significantly with the increase of soil moisture content (R 2 = 0.17-0.48, P < 0.05), while those in roots and whole plant of C. alatauensis showed peak and valley curve respectively (R 2 = 0.32-0.64, P < 0.05). The NSC and SS concentrations in stems and leaves of C. parvula showed unimodal curves respectively (R 2 = 0.68-0.88, P < 0.01), while those of C. alatauensis showed single valley curve patterns (R 2 = 0.28-0.75, P < 0.05). The dry matter (DM) allocation of NSC in leaves of both species was the lowest, and the DM NSC , DM SS and DM ST in organs and whole plant were significantly positively correlated with soil moisture content (R 2 = 0.18-0.64, P < 0.05), except those in roots and leaves of C. alatauensis . The SS concentration and DM ST in roots of C. parvula were the main contribution indexes to soil moisture changes, and the SS/ST in stems and leaves were increased with the decrease of soil moisture. The SS concentration and DM ST in leaves of C. alatauensis are the main contribution indexes to soil moisture changes, and the comprehensive control of DM NSC accumulation in stems and increased SS/ST in leaves was functioned to combat habitat drought. Article type: Primary Research Article Responses of biomass and non-structural carbohydrates to soil moisture gradient of two Carex species in alpine meadow in Southeast Qinghai-Xizang Plateau Authors: Zhongkui Li, Dacai Zhang * Key Laboratory of National Forestry and Grassland Administration on Biodiversity Conservation in Southwest China, Southwest Forestry University, Kunming, 650224, China * Corresponding author. E-mail: dczhang24@163. com Abstract Soil moisture changes affect the dynamics of plant biomass and non-structural carbohydrates (NSC), and different species have different response strategies. In the alpine meadow of Dongda Mountain in Southeast Qinghai-Xizang Plateau, 5 quadrats were set up respectively along the soil moisture gradient and experimental materials were collected by total harvest method. The NSC concentration was determined by modified phenol concentrated sulfuric acid method. The relationships between the biomass, NSC and soil moisture content of two Carex species were analyzed by One-way ANOVA, Two-way ANOVA, principal component analysis and polynomial fitting. The results showed that the root biomass of C. alatauensis , stem biomass of C. parvula and leaf, above-ground, below-ground and total biomass of two species were significantly positively correlated with soil moisture content (R 2 = 0.17-0.68, P < 0.05). The NSC, soluble sugar (SS) and starch (ST) concentrations in roots and whole plant of C. parvula all increased significantly with the increase of soil moisture content (R 2 = 0.17-0.48, P < 0.05), while those in roots and whole plant of C. alatauensis showed peak and valley curve respectively (R 2 = 0.32-0.64, P < 0.05). The NSC and SS concentrations in stems and leaves of C. parvula showed unimodal curves respectively (R 2 = 0.68-0.88, P < 0.01), while those of C. alatauensis showed single valley curve patterns (R 2 = 0.28-0.75, P < 0.05). The dry matter (DM) allocation of NSC in leaves of both species was the lowest, and the DM NSC , DM SS and DM ST in organs and whole plant were significantly positively correlated with soil moisture content (R 2 = 0.18-0.64, P < 0.05), except those in roots and leaves of C. alatauensis . The SS concentration and DM ST in roots of C. parvula were the main contribution indexes to soil moisture changes, and the SS/ST in stems and leaves were increased with the decrease of soil moisture. The SS concentration and DM ST in leaves of C. alatauensis are the main contribution indexes to soil moisture changes, and the comprehensive control of DM NSC accumulation in stems and increased SS/ST in leaves was functioned to combat habitat drought. Keywords: soluble sugar, starch, dry matter, allocation pattern, Carex alatauensis , C. parvula Introduction Plant growth is closely related to soil moisture (Vennam et al. , 2023), because soil moisture changes directly affect plant photosynthesis, substance synthesis and transport, while plants make morphological and physiological multiple adaptional adjustments (Li et al. , 2014). Biomass is the comprehensive expression of habitat change affecting plant growth and plant adaptation (Li et al. , 2017), it is the result of the long-term response of all physiological, biochemical and growth of plants to the habitat (Edwards et al. , 2004). With the decrease of soil moisture, the above-ground (AB), below-ground (BB) and total biomass of Medicago sativa are significantly affected, the BB/AB increased firstly and then decreased, and the water use efficiency and yield of M. sativa are improved by adjusting the above-ground and below-ground biomass allocation (Jiang et al. , 2014). The drought tolerance of Pinus tabulaeformis also significantly improved by increasing BB/AB level (Liu et al. , 2014). Non-structural carbohydrates (NSC) are important energy substances for plant growth and metabolism, of which more than 90% are soluble sugar (SS) and starch (ST) (Latt, et al. , 2001; Hoch et al. , 2002; Richardson et al. , 2012). Soil moisture affects the NSC dynamics of plants, but the relationship between NSC and soil moisture and the response mechanism of different species still need to be further clarified (Yang et al. , 2022; Wang et al. , 2023). The decrease of soil moisture causes changes in plant NSC concentration and distribution (Santos et al. , 2021), thus affecting plant physiological activities (Du et al. , 2014). With the decrease of soil moisture, SS concentration in plant tissues increased and directly participated in osmotic regulation. ST mainly plays a storage role and could be converted into SS when water was reduced to a certain extent (Thalmann et al. , 2017). The increase of SS concentration in plant above-ground tissue can enhance its drought tolerance under drought conditions (Blumstein et al. , 2022). For example, the decrease of soil moisture significantly increased the NSC concentration in the main branches of trees (Iwasaki et al. , 2020). Compared with water deficit, M. sativa root system was more sensitive to excessive water, and it has strong drought tolerance but not flood tolerance, excessive soil moisture reduced soil permeability and affected root respiration (Jiang et al. , 2014). Other studies have shown that severe or prolonged drought disrupted the carbon balance, and that the reduction of NSC dry matter (DM NSC ) leaded to carbon starvation and plant death (He et al. , 2020; Mcdowell et al. , 2022), it means the total amount of available NSC for conversion in the body is critical for plant growth and death (Chuste et al. , 2020). It can be seen that the production, storage and metabolism of NSC have a great impact on plant growth and environmental responses (Loewe et al. , 2000). NSC has different distribution and dynamics among different species and organs (Santos et al. , 2021; Wang et al. , 2023). The concentration and distribution pattern of NSC and its components in three temperate tree species were found to have inter-specific variation and significant differences among tree species and tissues ( P < 0.05). And the study on the dynamics of NSC in seven warm temperate deciduous broad-leaved trees showed that the species type had significant effects on the NSC concentrations in branches and leaves (Wang et al. , 2023). The concentrations of SS and ST in the roots, branches and leaves of Picea meyeri increased with decreasing soil moisture, except ST in the leaves (Yang et al. , 2022). The growth of Mongolian oak was slow but the concentration of NSC in roots was very high in arid habitat (Wang et al. , 2023). The high stress resistance of Carex alatauensis is directly related to the high concentration of NSC in the root collar (Zhu et al. , 2004). Plants tend to invest SS in the above-ground part, while ST is mainly stored in the trunk, and this kind of distribution pattern leads to a balanced distribution of NSC among different organs (Yu et al. , 2011). At the whole plant level, the decrease of soil moisture significantly decreased the whole plant NSC, SS and ST concentrations of Pinus radiata , but there was no significant change in the whole plant NSC concentration of Eucalyptus globulus and Eucalyptus smithii , while the ST concentration decreased significantly (Mitchell et al. , 2013). The alpine meadow ecosystem in Qinghai-Xizang Plateau is very sensitive to climate change and participates in the response to global change through its special energy-water exchange and carbon cycle changes (Wang et al. , 2007). Carex in the Cyperaceae family are cold-mesophilic, wet-mesophilic and dry-mesophilic subterranean budding herbaceous plants with short rhizomes, adapted to different climatic types (Wu et al. , 2012). C. alatauensis and C. parvula both highly resistant species, are the establishment species of Carex meadow (Li et al. , 2006). C. alatauensis usually grows in habitat with moderate soil moisture (Dang et al. , 2014), it has a weak ability to adapt to arid habitat. Meanwhile, C. parvula is a dry-mesophilic and drought-tolerant plant with a strong ability to adapt to arid habitat (Wu et al. , 2012) . This paper aims to study the changes of biomass and NSC of two Carex species with soil moisture content, and attempt to answer the following scientific issues: (i) How does soil moisture content change affect biomass dynamics and distribution patterns of two Carex species? (ii) Are NSC concentration and dry matter dynamics and distributions of two Carex species affected by soil moisture content change? (iii) Is there any inter-specific difference in the main contribution indexes of NSC in the two Carex species in response to soil moisture content change? 2. Materials and methods 2.1. Study site profile and quadrat setting The research site was located in the alpine meadow near Dongda Mountain bealock, southeast Qinghai-Xizang Plateau, with the geographical coordinates of 29°71′38″-29°71′92″N, 98°04′59″-98°04′66″E, and the altitude of the bealock is 5008 m. The terrain of the study site is concave, the terrain of ravine is flat, the stream runs through it, and the habitat is wet; sloping elevation on both sides and habitat tends to be drought (Zhang et al. , 2018; Yang et al. , 2022). C. parvula and C. alatauensis were the dominant species in the phytocoenosium. According to the natural distribution zone of the two Carex populations, five 5×5 m 2 quadrats were set up respectively, from the droughty habitat near the alpine screes to the wet habitat in the ravine. The Cp4 and Cp5 quadrats of C. parvula are overlap with Ca1 and Ca2 quadrats of C. alatauensis , respectively, and the two Carex species are co-dominant species in this region (Table 1). In the dry season (October), the TS-TW soil temperature and humidity rapid measuring instrument was used to measure the soil volumetric water content among 5 sample points in each quadrat, and the average value was taken as the soil moisture content of the quadrat. 2.2. Experimental material collection and processing Combined with the species morphological differences, earth boring auger (d = 3.5 cm) was used to extract 15 cm soil column of C. parvula ; customized cutting ring (d = 10 cm) was used to extract 10 cm soil column of C. alatauensis , and 5 soil columns were extracted from each quadrat. When taking NSC assay material, one 20×20×15 cm 3 soil block was randomly excavated in each soil moisture gradient quadrat to obtain healthy plants by total harvest method. After removing litters and other impurities in the station, clean up in 80 mesh nylon net and separate the roots, stems and leaves with scissors. All materials are dried with a unit heater and stored in a ziplock bag containing discolored silicone. Take all materials back to the laboratory and kiln dry it at 80℃ to constant weight in drying oven. The biomass was weighed with an analytical balance with the accuracy of 0.0001 g, and the NSC assay material was pulverized and stored in a ziplock bag containing discolored silicone for later experiments. 2.3. NSC concentration determination The SS and ST concentrations were determined by modified phenol concentrated sulfuric acid method (Blumstein & Hopkins, 2021). Extraction and concentration determination of SS: Weigh 50 mg powder sample with analytical balance (5 times repetition), grind and homogenize in mortar with distilled water (add a small amount of SiO 2 ), rinse and pour into centrifuge tube (10 ml) to make the sample liquid up to 8 ml. Boil in a water bath kettle for 30 min and centrifuge at 4000 r/min for 10 min. After centrifugation, pour the extracting solution into a volumetric flask and metered the volume to 100 ml. Add 1 ml distilled water, 1 ml 9% phenol and 5 ml concentrated sulfuric acid in turn to a glass test tube, shake well, and wait for color reaction at room temperature for 30 min. Using blank space as reference, the optical density was measured at the wavelength of 485 nm by ultraviolet-visible spectrophotometer (preheating 30 min), and the SS concentration was calculated from the standard curve. Extraction and concentration determination of ST: Distilled water was added to the SS residue to make the sample liquid in centrifuge tube up to 8 ml. After boiling for 15 min, 1 ml 9.2mol/L HCIO 4 was added and wait for static settlement for 15 min. Subsequent centrifugation, constant volume and determination procedure were consistent with SS concentration determination method. 2.4. Data processing and analyses According to the morphological characteristics of the two Carex species, the below-ground biomass is the sum of root and stem biomass, and the above-ground biomass is the leaf biomass. DM NSC (mg) was converted by combining the biomass (g) and NSC concentration (mg/g) data of each organ, DM NSC = biomass × concentration NSC , DM SS = biomass × concentration SS , DM ST = biomass × concentration ST . The Linear weighted sum method (LWSM) was used to calculate the NSC concentration of the whole plant based on the biomass allocation and NSC concentration differences in each organ. Taking the proportion of the biomass of each organ in the total biomass as the weight, the NSC concentration of each organ was multiplied by the corresponding weight and summed to obtain the NSC concentration of the whole plant (Mitchell et al. , 2013). NSC concentration of the whole plant = (root NSC concentration × root biomass / total biomass) + (stem NSC concentration × stem biomass / total biomass) + (leaf NSC concentration × leaf biomass / total biomass), and the calculation of SS and ST concentration of the whole plant can be deduced by analogy. Analyze data and draw plots with IBM SPSS Statistics 27 and Origin Pro 2024. The differences of NSC, SS, ST concentration, DM and biomass among soil moisture content were analyzed by using One-way ANOVA ( P < 0.05). Two-way ANOVA was used to analyze whether soil moisture content and different organs and their interactions have significant interaction on NSC concentration and dry matter accumulation of two Carex species. The correlation strength and response characteristics of biomass and NSC to soil moisture content were analyzed by scatter plot and polynomial fitting. When selecting the NSC indexes of two Carex species that contributed the most to soil moisture content change, eigenvalue, variance contribution rate and loading were obtained through principal component analysis (PCA), and the number of principal components was determined by extracting factors with eigenvalue > 1 according to the degree of variation. The greater the variance contribution rate, the more information about the original variable is included, and the cumulative contribution rate is required to be more than 80%. With the eigenvalue of each principal component as the weight and the variance contribution rate as the coefficient λ, the comprehensive evaluation model F was calculated by the expression F = (λ 1 F 1 + λ 2 F 2 ) / (λ 1 + λ 2 ), and then ranking according to F value (Yang et al. , 2022). 3. Experimental results and analysis 3.1. Relationship between biomass and soil moisture content of two Carex species The root biomass of C. alatauensis , stem biomass of C. parvula and leaf, above-ground, below-ground and total biomass of two Carex species were significantly positively correlated with soil moisture content (R 2 = 0.17-0.68, P < 0.05; Fig. 1a, b). The root biomass of C. parvula and stem biomass of C. alatauensis showed a peak and valley curve pattern respectively with the increase of soil moisture content (R 2 = 0.49, 0.45, P < 0.01; Fig. 1a, b). The biomass allocation of two Carex species was the largest in the root, and root biomass of C. parvula was significantly larger than stem and leaf biomass ( P < 0.05, Fig. 1a, b). The BB/AB of C. parvula was significantly larger than C. alatauensis ( P < 0.05). And there was a significant negative correlation between BB/AB of C. parvula and soil moisture content (R 2 = 0.45, P < 0.01; Fig. 1c), while the BB/AB of C. alatauensis showed a single valley curve pattern (R 2 = 0.35, P < 0.01; Fig. 1d). 3.2. Relationship between NSC concentration, DM NSC and soil moisture content of two Carex species Soil moisture content, different organs and their interactions had significant interaction effects on NSC, SS and ST concentrations, dry matter accumulation and SS/ST ratio of the two Carex species (Table 2). The NSC, SS and ST concentrations in roots and whole plant of C. parvula all increased significantly with the increase of soil moisture content (R 2 = 0.17-0.48, P < 0.05; Fig. 2a-c), while the concentrations of NSC, SS and ST concentrations in roots and whole plant of C. alatauensis showed peak and valley curve respectively with the increase of soil moisture content (R 2 = 0.32-0.64, P < 0.05; Fig. 2d-f). The NSC and SS concentrations in stems and leaves of C. parvula showed unimodal curves respectively (R 2 = 0.68-0.88, P < 0.01; Fig. 2a, b), while those of C. alatauensis showed single valley curve patterns (R 2 = 0.28-0.75, P < 0.05; Fig. 2d, e). The ST concentration in leaves of C. parvula showed a unimodal curve (R 2 = 0.40, P < 0.01; Fig. 2c), while ST concentration in leaves of C. alatauensis showed significantly positively correlated with soil moisture content (R 2 = 0.60, P < 0.01; Fig. 2f), and ST concentration in stems of C. alatauensis showed a single valley curve pattern (R 2 = 0.73, P < 0.01; Fig. 2f). The concentrations of NSC, SS and ST in stems of two Carex species were significantly higher than those in roots and leaves ( P < 0.05, Fig. 2), except for C. parvula ST. The DM NSC , DM SS and DM ST in roots, stems, leaves and whole plant of C. parvula and in roots and leaves of C. alatauensis were significantly positively correlated with soil moisture content (R 2 = 0.18-0.64, P < 0.05; Fig. 3). The DM NSC , DM SS and DM ST in stems and whole plant of C. alatauensis all showed single valley curve patterns with the increase of soil moisture content (R 2 = 0.53-64, P < 0.01; Fig. 3d-f). The DM NSC , DM SS and DM ST in roots of C. parvula were significantly higher than those in stems and leaves respectively ( P 0.05); while those of C. alatauensis were basically manifested as stems ＞ root ＞ leaves (Fig. 3d-f). 3.3. Relationship between SS/ST and soil moisture content of two Carex species The SS/ST in roots, stems, leaves and whole plant of two species showed various relationships with soil moisture content, but the ratio was the largest in the leaves of the most arid habitat (Fig. 4). The SS/ST in stems of C. parvula were significantly negatively correlated with soil moisture content (R 2 = 0.22-0.27, P < 0.05; Fig. 4a, b), in leaves showed a single valley curve pattern with the increase of soil moisture content (R 2 = 0.32, P < 0.05; Fig. 4a, b), in whole plant were significantly positively correlated with soil moisture content (R 2 = 0.33, P 0.05, Fig. 4a, b). The SS/ST in leaves and whole plant of C. alatauensis were significantly negatively correlated with soil moisture content (R 2 = 0.16-0.58, P 0.05, Fig. 4c, d). 3.4. Screening of main contribution indexes of NSC response to soil moisture content changes The results of principal component analysis showed that NSC concentration indexes of two Carex species had different contribution values in response to soil moisture content changes. The PC1 of C. parvula mainly included S-ST and L-ST, PC2 mainly included R-SS and R-ST, the cumulative variance contribution rate reached 84.75%, and R-SS was the largest contribution to soil moisture content changes. The PC1 of C. alatauensis mainly included L-SS and S-ST, PC2 mainly included L-ST, the cumulative variance contribution rate reached 84.46%, and L-SS was the largest contribution to soil moisture content changes (Table 3). The results of principal component analysis showed that DM NSC indexes of two Carex species had different contribution values in response to soil moisture content changes. The PC1 of C. parvula mainly included DM L-SS and DM L-ST , PC2 mainly included DM R-ST and DM R-SS , the cumulative variance contribution rate reached 82.40%, and DM R-ST was the largest contribution to soil moisture content changes. The PC1 of C. alatauensis mainly included DM R-SS and DM S-ST , PC2 mainly included DM L-SS and DM L-ST , the cumulative variance contribution rate reached 83.08%, and DM L-ST was the largest contribution to soil moisture content changes (Table 4). 1. Discussion 2. Asymmetric response of biomass to changes of soil moisture content The root biomass of C. alatauensis , stem biomass of C. parvula and leaf, above-ground, below-ground and total biomass of two Carex species were significantly positively correlated with soil moisture content (R 2 = 0.17-0.68, P < 0.05; Fig. 1a, b). This coincides with the above and below ground biomass of C. moorcroftii decreased with habitat drying, and above-ground biomass of C. tibetikobresia continue to reduce with soil moisture content decreased (Wang et al. , 2021; Dang et al. , 2014), it means the decrease of soil moisture limited the biomass accumulation of Carex species. The root biomass of C. parvula and stem biomass of C. alatauensis showed a peak and valley curve pattern respectively with the increase of soil moisture content (R 2 = 0.49, 0.45, P < 0.01; Fig. 1a, b). The variation characteristic of C. parvula supports the conclusion of previous study that the biomass of C. parvula increases first and then decreases with the decrease of soil moisture (Dang et al. , 2014), while stem biomass of C. alatauensis showed an opposite pattern of change. The biomass allocation of two Carex species was the largest in the roots, and roots biomass of C. parvula was significantly larger than stem and leaf biomass ( P < 0.05, Fig. 1a, b), this reflects the trade-off and allocation strategy of two Carex species to promote subsurface and inhibit above-ground biomass accumulation (Liu et al. , 2024) in response to droughty alpine meadow habitat. The BB/AB of C. parvula was significantly negatively correlated with soil moisture content (R 2 = 0.45, P < 0.01; Fig. 1c), this is similar to the BB/AB of Buchloe dactyloides in droughty habitat was significantly higher than that in wet habitat (Liu et al. , 2024), and the BB/AB of Pinus koraiensis and Fraxinus mandsurica in arid habitat were significantly higher than those in moist habitat, while the BB/AB of Juglans mandshurica and Tilia amurensis were decreased than those in moist habitat (Xiao et al. , 2004), and this pattern was opposite to that of C. parvula . The BB/AB of C. alatauensis showed a single valley curve pattern with the increase of soil moisture content (R 2 = 0.35, P < 0.01; Fig. 1d), this was consistent with the BB/AB trend of C. moorcroftii decreased firstly and then increased with habitat drying (Wang et al. , 2021). It proves that both excessive and low moisture content promoted the growth of the below-ground tissues of C. alatauensis . Both Carex species take the allocation strategy by increasing root and stem biomass and reducing leaf biomass to avoid over-consumption of limited water in the above-ground tissue, and this is related to the asymmetric response of morphological characteristics of plant organs, the sensitivity and trade-off strategy of each organ to water changes were shown also (Wang et al. , 2021). It was demonstrated that soil moisture content significantly affected the growth and development of two Carex species (Dang et al. , 2014), which was further manifested as biomass accumulation and distribution. 3. NSC dynamics and inter-specific variations in response to changes of soil moisture content The NSC concentration of the two Carex species is mainly dominated by SS concentration (Fig. 2), which is similar to the regulatory mechanism found in previous studies that the increase of plant NSC concentration is mainly caused by the change of SS concentration (Wang et al. , 2023) and that plants mainly enhance their osmotic ability by increasing SS concentration (Du et al. , 2014). The concentrations of NSC and SS in the leaves of Ulmus pumila , Musa AA Pisang Mas and M. ABB Pisang awak increased during moderate drought, but decreased significantly during extreme drought (Wang et al. , 2010; Wang et al. , 2019), the NSC and SS concentrations in stems and leaves of C. parvula and the NSC、SS and ST concentrations in roots of C. alatauensis all showed unimodal curves respectively (Fig. 2), the results indicated that moderate drought might promote NSC concentration in plants. The NSC, SS and ST concentrations in roots and whole plant of C. parvula all increased significantly with the increase of soil moisture content (R 2 = 0.17-0.48, P < 0.05; Fig. 2a-c). This is similar to the trend that SS concentration in fine roots of Juglans mandshurica increased with the increase of soil moisture content (Ji et al. , 2023), and demonstrated that severe water deficit significantly decreased the NSC concentration in C. parvula and whole plant, and was opposite to that water deficit increased NSC concentration in roots (Chuste et al. , 2020; Leuschner, 2020) and the whole plant (Mitchell et al. , 2013). The concentrations of NSC and SS in stems, leaves and whole plant of C. alatauensis remained at very high levels in extremely arid habitat, which was contrary to the change pattern of C. parvula . Moreover, drought significantly increased the NSC and SS concentrations in non-grass functional groups (Song et al. , 2020) and severe drought promoted the NSC concentrations in various organs of Reaumuria soongorica (Shi et al. , 2022), indicating that different plant species have different response characteristics of NSC indexes when faced with water content changes in habitat. Furthermore, there are significant differences between species and even opposite adaptation strategies. The SS of each organ of the two Carex species was significantly higher than that of ST ( P < 0.05), and the SS/ST ratio was the highest (6.31 times) in the most dry habitat (Fig. 4). Plants can adjust cell osmotic potential according to soil moisture changes, and maintain turgor by maintaining high SS concentration in leaves and cell water content, so as to ensure various physiological activities (Iannucci et al. , 2002). SS/ST can be used as the conversion index of SS and ST, and the higher ratio means the greater demand for SS. For example, the decrease of soil moisture significantly increased SS/ST in roots, stems and leaves of Caryopteris mongolica (Shen et al. , 2019), and drought treatment enhances SS/ST by increasing the conversion from ST to SS in sapwood of Dalbergia odorifera (Cui et al. , 2022). Dry habitat induced a decrease in leaf osmotic potential, impeded the transport of photosynthetic products, and actively hydrolyzes sugars, thus leading to an increase of SS in leaves (Shi et al ., 2023), this mechanism may be related to the very low organ biomass but still very high SS/ST level of two Carex species in extremely dry habitat. The SS/ST in stems of C. parvula and in leaves and whole plant of C. alatauensis were significantly negatively correlated with soil moisture content (R 2 = 0.16-0.58, P < 0.05; Fig. 4), which are similar to SS concentration in the roots and shoots of Juglans regia was higher and ST concentration was lower under drought conditions (Naser et al. , 2010), indicating that SS, as an intracellular solute in plants, has an important drought-resistant effect. And the increase of SS/ST can help plants regulate osmotic potential to maintain water transport efficiency between leaves and roots (Sala et al. , 2012). However, there was a significant positive correlation between SS/ST in whole plant of C. parvula and soil moisture content (R 2 = 0.33, P < 0.05; Fig. 4a, b), contrary to the change pattern of C. alatauensis , it may be related to the different patterns in DM NSC of two Carex species with soil moisture content changes, and the accumulation of DM NSC between different species affects the transformation mechanism of SS and ST. The dynamics of NSC reflect the carbon balance of plants under environmental changes such as water deficit (Yang et al. , 2022). When the newly synthesized NSC is insufficient, the stored NSC can play a regulating and buffering role. If the consumption demand is still not met, the carbon budget balance will be broken, resulting in insufficient supply of NSC and carbon starvation (He et al. , 2020; Mcdowell et al. , 2022; Chen et al. , 2022). It is inferred that the sharp decrease of NSC concentration and DM NSC in the stems, leaves and whole plant of the C. parvula in the extremely dry habitat is related to the breakdown of carbon balance. The DM NSC , DM SS and DM ST in different organs and whole plant of C. parvula and in roots and leaves of C. alatauensis were significantly positively correlated with soil moisture content (R 2 = 0.18-0.64, P < 0.05; Fig. 3). This is consistent with the conclusion that the decrease of soil moisture content reduced the total amount of SS and ST in fine roots, stems and leaves of Robinia pseudoacacia (Wang et al. , 2015), which proves that the decrease of soil moisture content can reduce the accumulation of DM NSC . It was screened by PCA comprehensive sorting model that the main contribution indexes of C. parvula in response to soil moisture content change were SS concentration and DM ST in roots, while that of C. alatauensis were SS concentration and DM ST in leaves (Table 3, 4), indicating that the comprehensive regulation of SS concentration and DM ST of C. parvula can enhance its tolerance to dry habitat. On the other hand, the SS concentration and DM ST in leaves of C. alatauensis are extremely sensitive to soil moisture content changes (Leuschner, 2020) and play a major role of adaptive regulation. The different NSC concentration and DM NSC responses of two Carex species reflect that different species adapt to soil moisture change through a multi-channel comprehensive regulation. 4. Different NSC allocation patterns of two Carex species Two-way ANOVA analysis showed that soil moisture content, different organs and their interactions had significant interaction effects on NSC, SS and ST concentrations, dry matter accumulation and SS/ST ratio of the two Carex species (Table 2). The results indicated that the changes of soil moisture content affected the dynamics and distribution of NSC in the organs of two Carex species, and then affected the distribution patterns of NSC in different species. Soil moisture content changes affect NSC allocations among different organs, and the allocation patterns varies among different species. The DM NSC , DM SS and DM ST in roots of C. parvula were significantly higher than those in stems and leaves ( P < 0.05, Fig. 3a-c), this is similar to the studies on Fraxinus excelsior and M. sativa that roots are the main repositories of NSC (Gaucher et al. , 2005; Zhu et al. , 2018). The allocation of NSC is related to the carbon source, sink and the intensity, and leaves are the NSC source of the whole plant, while the growth of roots is an important NSC sink with a large amount of carbon (Yu et al. , 2011). For example, in dry habitat, plants often transfer newly synthesized carbohydrates to the roots to enhance the absorption of water and mineral ions (Shen et al. , 2019; Zhai et al. , 2022) and accumulate NSC in the roots (Santos et al. , 2023; Wang et al. , 2023). U. pumila allocates more nutrient resources to roots with increasing drought intensity (Wang et al. , 2019), indicating that roots are an important carbon sink and are conducive to plant growth in dry habitat. The allocation patterns of DM NSC , DM SS and DM ST in C. alatauensis were basically manifested as stem is the largest among different organs (Fig. 3d-f). Plants often store photosynthetic products in roots and stems to adapt to unfavorable environments (Gömez et al. , 2010; Slewinski et al. , 2012), it is generally believed that a large amount of carbohydrates stored in stems of plant played a buffering role in sourcing-sink coordination (Ruuska et al. , 2006), and NSC in stem enhanced the resistances of plants to drought and other stresses (Gömez et al. , 2010). When the growth of a reservoir organ of a plant is sensitive to water content change, the photosynthetic products will be preferentially allocated to the organs (roots or stems) with strong storage capacity for utilize or storage (Yang et al. , 2020). The accumulation of DM NSC , DM SS and DM ST in the stems of C. alatauensis may be related to the role and mechanism of the stems mentioned in the above studies. It can be seen that source-sink coordination and NSC differential allocation patterns are important ecological adaptation strategies to enhance stress resistance and maintain growth, development and reproductive evolution of the two Carex species in high altitude and arid environment. 5. Conclusions Under each soil moisture content, the two Carex species both invested the most resources in roots and reduced the growth of above-ground parts to enhance water use efficiency and drought tolerance. Both two Carex species maintained a high concentration of NSC in stems to ensure that the source-sink coordination function was played in the process of NSC production and consumption in the shortest distance and the fastest time. In addition, C. parvula as a drought-tolerant plant, SS concentration and DM ST in roots were the main contribution indexes to soil moisture changes, and the SS/ST in stems and leaves were increased with the decrease of soil moisture. C. alatauensis is a wet-mesophilic plant, the SS concentration and DM ST in leaves are the main contribution indexes to soil moisture changes, and the comprehensive control of DM NSC accumulation in stems and SS/ST in leaves both increased were used to combat dry habitat. The multi-regulatory mechanisms of biomass allocation, NSC concentration dynamics and DM NSC accumulation correspond to that the two Carex species belong to different water-dependent types and manifested strong adaptability to the drought of alpine meadow habitat. Acknowledgments This work was supported by the National Natural Science Foundation of China (Response to arid habitats for bud bank and growth dynamics of roots and stems underground in an alpine meadow, grant number: 31960340). Conflict of interest The authors have no conflicts of interest to declare. References Blumstein M, Hopkins R. 2021. Adaptive variation and plasticity in non-structural carbohydrate storage in a temperate tree species. 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Pratacultural Science , 21(12): 64-68. https://doi.org/10.3969/j.issn.1001-0629.2004.12.014 Table 1 Quadrats information No. of quadrat Soil moisture content (%) Altitude (m) Longitude and latitude Dominant species Cp1 10.17 4868.6 29°71′38″N, 98°04′64″E C. parvula Cp2 15.60 4816.5 29°71′58″N, 98°04′60″E C. parvula Cp3 20.63 4801.5 29°71′66″N, 98°04′64″E C. parvula Cp4, Ca1 25.00, 23.12 4798.1, 4816.7 29°71′68″N, 98°04′62″E, 29°71′58″N, 98°04′60″E C. parvula , C. alatauensis Cp5, Ca2 30.37, 32.64 4802.1, 4803.6 29°71′66″N, 98°04′61″E, 29°71′64″N, 98°04′59″E C. parvula , C. alatauensis Ca3 42.62 4800.9 29°71′65″N, 98°04′59″E C. alatauensis Ca4 52.56 4793.0 29°71′92″N, 98°04′66″E C. alatauensis Ca5 63.04 4797.1 29°71′69″N, 98°04′62″E C. alatauensis Table 2 Two-way ANOVA on the effects of soil moisture content and organ on NSC of two Carex species Source of variations C. Parvula (F value) C. alatauensis (F value) SMC Organ SMC × Organ SMC Organ SMC × Organ Concentration NSC 319.28 * 959.83 * 113.45 * 325.03 * 17705.15 * 213.01 * SS 281.36 * 1873.84 * 141.85 * 446.09 * 19645.97 * 317.99 * ST 92.93 * 261.71 * 21.56 * 47.23 * 3937.67 * 54.79 * SS/ST 26.45 * 355.63 * 19.31 * 84.44 * 1588.26 * 93.1 * DM NSC 16.59 * 665.58 * 6.93 * 18 * 54.19 * 5.29 * SS 17.48 * 608.68 * 6.8 * 16.89 * 48.88 * 5.06 * ST 14.78 * 778.88 * 7.37 * 20.54 * 71.92 * 6.24 * SS/ST 10.01 * 113.75 * 6.28 * 10.85 * 198.54 * 12.74 * Note: The acronyms in the table represent: SMC, soil moisture content; NSC, non-structural carbohydrates; SS, soluble sugar; ST, starch; DM, dry matter. * represents significant difference at P < 0.01. The same as below. Table 3 Factor loadings and rank of principal components in NSC concentration Indexes of two Carex species Indexes C. parvula Indices C. alatauensis Factor loading F Rank Factor loading F Rank F 1 F 2 F 1 F 2 R-SS 0.365 0.553 0.429 1 L-SS 0.469 0.099 0.386 1 R-ST 0.362 0.553 0.427 2 S-ST 0.464 0.028 0.366 2 S-ST 0.491 -0.099 0.291 3 L-ST 0.005 0.884 0.203 3 L-ST 0.448 -0.058 0.276 4 S-SS 0.360 -0.433 0.181 4 L-SS 0.413 -0.401 0.136 5 R-SS -0.465 -0.081 -0.379 5 S-SS 0.350 -0.462 0.074 6 R-ST -0.467 -0.117 -0.388 6 Eigenvalues 3.356 1.729 3.924 1.144 Percentage of Variance (%) 55.931 28.820 65.393 19.068 Cumulative (%) 55.931 84.751 65.393 84.460 Note: The acronyms in the table represent: R-SS, root soluble sugar; R-ST, root starch; S-SS, stem soluble sugar; S-ST, stem starch; L-SS, leaf soluble sugar; L-ST, leaf starch. The same as below. Table 4 Factor loadings and rank of principal components in DM NSC Indexes of two Carex species Indexes C. parvula Indices C. alatauensis Factor loading F Rank Factor loading F Rank F 1 F 2 F 1 F 2 DM R-ST 0.285 0.592 0.376 1 DM L-ST 0.406 0.538 0.435 1 DM L-ST 0.483 0.104 0.372 2 DM L-SS 0.363 0.522 0.398 2 DM L-SS 0.487 0.087 0.369 3 DM R-ST 0.395 0.080 0.327 3 DM R-SS 0.336 0.394 0.353 4 DM R-SS 0.430 -0.123 0.310 4 DM S-ST 0.435 -0.439 0.178 5 DM S-ST 0.431 -0.415 0.248 5 DM S-SS 0.383 -0.531 0.114 6 DM S-SS 0.420 -0.495 0.222 6 Eigenvalues 3.491 1.453 3.906 1.079 Percentage of Variance (%) 58.184 24.215 65.102 17.980 Cumulative (%) 58.184 82.399 65.102 83.082 Figure legends Figure 1. The relationship between biomass of two Carex species and soil moisture content Figure 2. The relationship between NSC concentration of two Carex species and soil moisture content Note: Whole plant NSC, SS and ST represent a weighted quantity for plant organ (based on the contribution of each organ to total biomass). The same as below. Figure 3. The relationship between DM NSC in two Carex species and soil moisture content Figure 4. SS/ST changes in different organs of two Carex species Information & Authors Information Version history V1 Version 1 09 January 2025 Peer review timeline Published BMC Plant Biology Version of Record 27 Aug 2025 Published Copyright This work is licensed under a Non Exclusive No Reuse License. Keywords allocation pattern dry matter growth soluble sugar starch storage carbohydrates Authors Affiliations Zhongkui Li 0009-0006-1355-7811 Southwest Forestry University View all articles by this author Dacai Zhang [email protected] Southwest Forestry University View all articles by this author Metrics & Citations Metrics Article Usage 210 views 200 downloads .FvxKWukQNSOunydq8rnd { width: 100px; } Citations Download citation Zhongkui Li, Dacai Zhang. Responses of biomass and non-structural carbohydrates to soil moisture gradient of two Carex species in alpine meadow in Southeast Qinghai-Xizang Plateau. Authorea . 09 January 2025. DOI: https://doi.org/10.22541/au.173640387.74289933/v1 If you have the appropriate software installed, you can download article citation data to the citation manager of your choice. Simply select your manager software from the list below and click Download. For more information or tips please see 'Downloading to a citation manager' in the Help menu . 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