Intercropping reduces soil erosion, improves soil conditions, and increases productivity of a Camellia oleifera plantation

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Lamont, and 3 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7271330/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 22 Dec, 2025 Read the published version in Plant and Soil → Version 1 posted 6 You are reading this latest preprint version Abstract Background and aims Camellia oleifera, a tree species of significant ecological interest and economic value, is widely cultivated in China for its oil production. However, many C. oleifera plantations, particularly in the red soil regions of the Yangtze River Basin and southern China, show low productivity due to soil quality limitations. We hypothesized that intercropping would reduce soil erosion, improve soil conditions, and increase C. oleifera productivity. Methods To test this hypothesis, we intercropped C. oleifera with three herb species, Parthenocissus tricuspidata, Coreopsis lanceolata, and Mentha haplocalyx, in subtropical Hunan. Results Compared with monoculture, intercropping reduced runoff by 33.9–51.4%, soil loss by 72.4–84.3%, total nitrogen loss by 34.4–56.9%, and total phosphorus loss by 48.0–60.1%. Intercropping also modified soil microbial community composition, enhancing alpha diversity and promoting beneficial taxa such as Acidobacteria (31 – 116%) and Verrucomicrobia (15 – 820%). Furthermore, intercropping increased soil organic carbon by 7.4–53.8%, soil phosphorus by 2.3–56.4%, and soil urease activity by 40.4–86.0%. Most importantly, intercropping increased C. oleiferaproductivity, with the C. oleifera - Parthenocissus tricuspidata treatment yielding the highest total fruit production (134% greater than the control) and the highest total oil yield (157 kg ha⁻¹). Conclusions These findings support our hypothesis and demonstrate that intercropping is a sustainable land management practice for mitigating soil erosion, enhancing soil health, and boosting productivity in agroforestry systems. Camellia oleifera Intercropping treatments Soil physical and chemical properties Soil erosion and nutrients loss Soil microbial community Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 1. Introduction Camellia oleifera is a tree species of considerable horticultural importance, valued for its edible oil and ornamental appeal due to its colourful flowers. It is widely cultivated in Europe, North America, and Asia (Páscoa et al., 2018 ; Teixeira and Sousa, 2021 ; Ye et al., 2023 ). In China, C. oleifera is grown widely for oil production, with plantations reaching 4.9 million hectares spread over 15 provinces, including Hunan, Jiangxi, and Guangxi ( https://www.gov.cn/ ). However, many of these plantations, especially those in the red soil regions of the Yangtze River Basin and southern China, suffer from low productivity due to soil quality limitations (Chen et al., 2023 ; Liu et al., 2017 ; Liu et al., 2018 ; Tan et al., 2024 ; Tu et al., 2019 ). Red soils, which dominate subtropical China, are highly susceptible to erosion because of their poor structure, low organic matter content, and susceptibility to compaction (Gao et al., 2023 ; Zhang et al., 2004 ; Zhang et al., 2012 ). This vulnerability is further exacerbated by the region's hilly terrain and intense summer rainfall, characterized by short, heavy rainstorms (Li et al., 2022 ; Li et al., 2013 ; Yim et al., 2013 ) ( http://www.nmc.cn/ ). The combination of these factors leads to severe soil runoff and nutrient loss, reducing the productivity of C. oleifera plantations (Chen et al., 2023 ; Li et al., 2019 ; Zhang et al., 2024 ). Addressing these challenges is critical to improving the sustainability and yield of cultivated C. oleifera in these regions. Intercropping is the practice of growing several crop species together and is effective for reducing soil erosion by enhancing ground cover and improving soil structure (Brooker et al., 2015 ; Jensen et al., 2015 ). It is widely practiced in agricultural cropping systems and to a lesser extent in agroforestry systems. The combined canopy cover protects the soil from the direct impact of raindrops, which is a primary cause of soil particle disintegration and erosion (Liu et al., 2025 ). Additionally, the diverse root systems of intercropped plants, such as deep-rooted and shallow-rooted species, stabilize the soil matrix and reduce runoff. For instance, legumes with taproots and cereals with fibrous roots create a network that binds soil particles, minimizing soil erosion (Brooker et al., 2015 ). This synergistic effect not only preserves topsoil but also maintains soil fertility, making intercropping a sustainable solution for erosion-prone areas. Intercropping can also enhance crop productivity by optimizing resource use and promoting environmental synergies (Liu et al., 2019 a; Ramirez-Garcia et al., 2015 ). The combination of crops with different growth and resource requirements allows for more efficient utilization of sunlight, water, and nutrients (Letourneau et al., 2011 ; Lithourgidis et al., 2011 ). For example, tall crops, such as maize, can provide shade for shade-tolerant species, such as beans, reducing water evaporation and improving microclimatic conditions (Kumari and Choudhary, 2022 ). These interactions result in higher overall yields compared with monoculture systems, demonstrating the potential of intercropping to increase agricultural productivity while maintaining ecosystem stability. Furthermore, intercropping fosters a dynamic and resilient soil microbiome (Lu et al., 2023 ; Zhao et al., 2022 ). The presence of multiple plant species in intercropping systems leads to the exudation of diverse root secretions, such as sugars, amino acids, and organic acids, that serve as substrates for various microbial populations (Bais et al., 2006 ). For example, legumes in intercropping systems release flavonoids and other compounds that attract beneficial rhizobacteria and mycorrhizal fungi that play key roles in nutrient cycling and plant health (Hauggaard-Nielsen et al., 2009 ). In maize-bean intercropping systems, studies have shown increased abundance and activity of nitrogen-fixing bacteria, such as Rhizobium , and phosphate-solubilizing microbes, that enhance nutrient availability for both crops (Li et al., 2009 ). Moreover, intercropping promotes the coexistence of microbial taxa with complementary functions, such as decomposers, nitrogen fixers, and pathogen suppressors. In cereal-legume intercropping systems, the decomposition of legume residues provides organic matter that supports saprophytic fungi and bacteria, while the cereal roots create a habitat for nitrifying and denitrifying bacteria (Brooker et al., 2015 ). This functional diversity enhances ecosystem stability and productivity. To address soil erosion and low productivity of C. oleifera plantations, we introduced three plant species, Parthenocissus tricuspidata ( PT ), Coreopsis lanceolata ( CL ), and Mentha haplocalyx ( MH ), into a C. oleifera plantation in subtropical Hunan, China. We hypothesized that intercropping would reduce soil erosion, enhance soil nutrients and microbial activity, and increase the productivity of C. oleifera plantations. The three intercropping species were chosen because their ecological and agronomic traits complement those of C. oleifera , making them ideal for studying the potential benefits of intercropping. Parthenocissus tricuspidata (family Vitaceae) is a fast-growing climbing vine originating in East Asia. It has the ability to quickly cover surfaces, making it an ideal species for preventing soil erosion. Moreover, it can adapt to diverse soil conditions and tolerate shady environments (Wang et al., 2010 ), making it a perfect companion for C. oleifera plantations. Coreopsis lanceolata (family Asteraceae) is a perennial herb native to North America ( https://plants.usda.gov/ ) and widely distributed in subtropical China. Mentha haplocalyx (family Lamiaceae) is a common aromatic perennial herb in East Asia and is highly valued for its rich essential oil content (An et al., 2024 ). Both species have thick, dense foliage, which helps to retain soil moisture and improve the soil microbial activities, thus promoting the overall health of the intercropped system (Shi et al., 2018 ). In addition, both species are known for their ability to grow in dry and infertile soils (Folgate and Scheiner, 1992 ; Wang et al., 2009 ; Zhou et al., 2021 ), making them highly suitable for intercropping. Our study had three objectives: (1) to examine how intercropping affects soil physical and chemical properties, as well as soil microbial communities; (2) to evaluate the effectiveness of different intercropping systems in reducing soil erosion and nutrient loss; and (3) to assess the impact of intercropping on C. oleifera fruit yield and quality. Ultimately, we aimed to determine the most effective intercropping system to minimize soil erosion and improve overall productivity for C. oleifera plantations in the red soil regions. 2. Material and methods 2.1 Site description The study was conducted in a Camellia oleifera plantation in Shaoyang County (26°54′N, 111°22′E), Hunan Province, China. This area has a humid subtropical monsoon climate, with an average annual temperature of 18.3℃ and average annual sunshine of 1610 hours (Liu et al., 2019 b). The soil is mainly red soil developed from Quaternary red clay. Soil depth is usually deeper than 80 cm. Total annual rainfall is 1300 mm with the rainy season from April to June with an average rainfall of 545.4 mm. The dry season is from July to September with an average rainfall of 273.1 mm. Soil erosion is most severe during the rainy season. 2.2 Intercropping treatment In 2014, the intercropping treatment was conducted on a hilly site with a slope of 13–17 degrees. Leveled planting beds (approximately 1 m wide) were prepared at 3 m intervals. Three-year-old C. oleifera (CO) seedlings were planted in a monoculture arrangement (3 × 3 m spacing) on these beds (Fig. 1 ). Compound fertilizer (25% N, 10% P, and 5% K) was applied at 550–600 kg ha − 1 at the time of planting. Weeding was done twice (May and October). In April, 2018, twelve 15 × 20 m plots in the C. oleifera plantation were selected. Plots were spaced at 5 m minimum Distance. Nine of the plots were randomly intercropped with Parthenocissus tricuspidata ( PT ), Coreopsis lanceolata ( CL ), and Mentha haplocalyx ( MH ). Hereafter, these treatments are referred to as CO-PT , CO-CL , and CO-MH , respectively. The other three plots were used as controls ( C. oleifera monoculture). For the CO-PT treatment, P. tricuspid ata seedlings were planted at 0.5 × 0.75 m. For the CO-C L treatment, C. lanceolata seedlings were planted at 0.5 × 0.75 m. For the CO-MN treatment, M. haplocalyx seedlings were planted at 0.5 × 0.75 m. 2.3 Runoff collection system To monitor soil erosion, a run-off collection system was set up within each plot (Fig. 1 ). The size of the system was 7 × 16 m. The long edge of the system was perpendicular to the contour line and the short edge was horizontal to the contour line. The system was separated from the surrounding area with an impermeable PVC hardboard buried 20 cm deep and 20 cm above ground. A drainage ditch was set up at the lower side of the system. In the system, runoff was piped and stored in the collection tanks (80 × 90 cm, diameter × height). We used a three-tank setup to account for the overflow of the system (Adimassu et al., 2020 ; Huo et al., 2020 ). The first tank was connected directly to the collection ditch with a PVC pipe. There were 10 diversion holes of 2 cm in diameter 60 cm above the bottom of the tank in the tank. One of the holes was connected to the second tank that was placed 50 cm lower than the first tank. The second tank, similar in setup to the first tank was connected to the third tank and was placed 50 cm lower than the second tank. The runoff collection was calculated as $$\:Run\:off\left({m}^{3}\bullet\:{ℎa}^{-1}\right)=Tank\:1+tank\:2\times\:10+tank\:3\times\:100\left(2\right)$$ 1 The daily rainfall was recorded by a HOBO data logging rain gauge 3 (Onset Computer Corporation, USA) installed in the open area at the study site during June-August 2020. During June-August 2020, there were five rainfall events. Runoff was collected and measured immediately after each rainfall event. The runoff from all three tanks was combined and mixed thoroughly. Three 1-L subsamples were collected and returned to the laboratory for further analysis. In the laboratory, each 1-L subsample was divided into two parts. One part was used to estimate the amount of sediment in the runoff. The resultant suspensions were filtered using Whatman 42 filter paper with a pore size of 2.5 µm. The sediment in the filter paper was oven-dried at 105°C for 24 h and weighed to obtain soil loss data. The other part was used for nutrient analysis. The total N and P concentrations were determined by potassium persulfate oxidation ultraviolet spectrophotometry and potassium persulfate oxidation molybdenum antimony resistance colorimetry (Zhang et al., 2021 ). Soil loss was calculated as per the equations given below: $$\:Soil\:loss\left(kg\:{ℎa}^{-1}\right)=\frac{Sediment\:weigℎt\left(g\:{m}^{-3}\right)\times\:Runoff\left({m}^{-3}{ℎa}^{-1}\right)}{{10}^{3}}$$ 2 Nutrient loss was calculated as per the equations given below: $$\:Nutrient\:loss\left(g\:{ℎa}^{-1}\right)=\frac{Nutrent\:content\left(g\:{m}^{-3}\right)\times\:Runoff\left({m}^{-3}{ℎa}^{-1}\right)}{{10}^{3}}$$ 3 2.4 Fruit yield and oil content of C. oleifera To compare the effects of intercropping on seed yield and quality of C. oleifera , we randomly selected three C. oleifera trees from each of the treatment plots and collected their fruits in October 2020. In total, 36 samples were collected (4 treatments × 3 replicate plots × 3 trees per plot). All fruits from each tree were harvested and weighed on-site. Three samples of about 500 g of the fruits from each plot were then brought to the laboratory for fruit trait determination. We first separated the pericarp, seed coat, and kernel and weighed them individually. They were then dried at 100–105℃ for 72 h or until constant weight was reached to give dry weight. Oil content of the kernel was measured by the Soxhlet extractor method (Ye et al., 2021 ; Yu et al., 2023 ). The following equations were used to analyze fruit quality traits (Lu et al. 2022 ; Ye et al. 2021 ): \(\:Total\:fruit\:yield\:\left(kg\bullet\:{ℎa}^{-1}\right)=\frac{Total\:fruit\:weigℎt\:per\:tree\times\:1156}{10000}\) (4) \(\:Average\:fruit\:weigℎt=\frac{Tℎe\:weigℎt\:of\:wℎole\:tℎe\:tree\:fruit\:}{Fruit\:number}\) (5) \(\:Oil\:content\left(\%\right)=\frac{Oil\:weigℎt}{Fruit\:weigℎt}\times\:100\%\) (6) \(\:Oil\:yield\left(kg\bullet\:{ℎa}^{-1}\right)=Total\:fruit\:yield\:per\:ℎa\:\times\:Oil\:content\) (7) There were 1156 C. oleifera trees per hectare. 2.5 Soil physical and chemical properties and microbial diversity Three replicate soil samples (0–30 cm) were collected from each treatment plot using a soil drill, totaling 36 samples (4 treatments × 3 plots × 3 replicate samples). The samples were placed in an ice box before transport to the laboratory. Here, each soil sample was then divided into two parts, one was used for measuring soil urease activity, polyphenol oxidase activity and soil microbial diversity. It was stored at -80°C until used. The other part of the soil sample was used for analysis of SOC, TN and total phosphorus (TP). Soil urease activity, which measures the extracellular enzyme produced by bacteria and fungi and plant roots, was measured by phenol sodium-sodium hypochlorite colorimetric method (Domínguez et al., 2017 ). Soil polyphenol oxidase (PO, compounds related to polymerization of phenolic materials) was determined by pyrogallol colorimetric method (Wang et al., 2022 ). Soil microbial diversity (Sobs index for richness and Shannon index for diversity) was measured by the high-throughput sequencing technology (Chaudhary et al., 2021 ). Soil organic matter was measured by the dichromate oxidation method (Bao, 2000 ). total nitrogen was measured by the Kjeldahl method (Tong and Liu, 2020 ). Total phosphorus was measured by the ascorbic acid method (Bao, 2000 ). Soil pH was measured using the electrode potential method (Bao, 2000 ). 2.6 Statistical analyses One-way ANOVAs and Tukey’s tests were used to analyze the effect of intercropping on the yield of fruit and oil yield, soil physical and chemical properties, total water loss, total soil loss, total nitrogen and phosphorus loss, soil bacterial and fungal diversity, and abundance. Correlation analysis was used to assess the effects of fruit properties and soil physical and chemical properties, runoff, and soil erosion. Significance was accepted at P < 0,05. All data were analyzed by IBM SPSS statistics software (version 21.0) and Origin Pro 2016 software. 3. Results 3.1 The effects of intercropping on fruit and oil yield Total fruit and oil yield varied significantly between the intercropping treatments and control (Table 1 ). The CO-PT treatment produced the highest total fruit yield, which was 134% higher than that of the control ( P < 0.05). In contrast, the CO-MH treatment had the lowest average fruit weight (14.4 g), significantly lower than the other two intercropping treatments and the control (19.9 to 28.0 g). However, oil content was significantly higher in CO-MH (8.6%) than the other intercropping treatments and the control (5.8 to 6.7%). The total oil yield was highest in CO-PT (157 kg ha − 1 ), which was significantly higher than that of the control and the CO-MH treatment. Oil content was negatively correlated with the three erosion-related indices: runoff, soil loss, and TN loss (Fig. 2 ). Additionally, oil content (percentage of oil in the fruit) showed a negative correlation with total fruit yield and soil total phosphorus (TP) loss, though these correlations were only marginally significant ( P = 0.07 and P = 0.09, respectively). Table 1 Effects of intercropping on fruit and oil yield of a Camellia oleifera plantation Fruit and oil production Intercropping treatment Control CO-PT CO-CL CO-MH Total fruit yield (kg ha − 1 ) 1093 ± 263b 2554 ± 678a 1642 ± 277ab 1003 ± 192b Average fruit weight (g) 19.86 ± 2.63ab 26.34 ± 4.73a 27.96 ± 3.7a 14.37 ± 2.09b Oil content (%) 5.76 ± 0.34b 6.72 ± 0.44b 6.40 ± 0.29b 8.64 ± 0.67a Total oil yield (kg ha − 1 ) 64.22 ± 15.74b 156.89 ± 34.64a 100.77 ± 13.95ab 84.23 ± 15.35b All data are shown as mean± standard error (n = 9). Different letters in the same row represent significant differences ( P < 0.05) by Tukey’s test. Intercropping treatment: Control: C. oleifera monoculture, CO-PT: C. oleifera + Parthenocissus tricuspidata , CO-CL : C. oleifera + Coreopsis lanceolata , CO-MH : C. oleifera + Mentha haplocalyx . 3.2 The effects of intercropping on soil chemical and physical properties Intercropping strongly influenced soil chemical and physical properties (Table 2 ). Compared with the control, intercropping increased soil organic carbon (SOC) by 7.4 to 53. 8%, TP by 2.3 to 56.4%, and soil urease activity by 40.4 to 86.0%. Intercropping also increased soil polyphenol oxidase (PO) content by 21.8% and 10.5% in CO-CL and CO-MH treatments, respectively, compared with the control, wheeas no significant change was observed in the CO-PT treatment. In contrast, intercropping decreased soil total nitrogen (TN) by 9.5 to 33.5%. Soil pH in the control was similar to that of CO-PT but lower than that of CO-CL and CO-MH , but, soil bulk density showed little variation between the intercropping treatments and the control (Table 2 ). Table 2 Effects of intercropping treatments on soil properties of a Camellia oleifera plantation Soil properties Intercropping treatment Control CO-PT CO-CL CO-MH SOC (g kg − 1 ) 8.87 ± 0.99b 9.53 ± 0.83b 13.64 ± 0.76a 13.09 ± 0.83a TN (g kg − 1 ) 1.58 ± 0.17a 1.31 ± 0.09ab 1.05 ± 0.1b 1.43 ± 0.13a TP (mg kg − 1 ) 397 ± 48b 621 ± 108a 545 ± 17ab 406 ± 62b Urease (mg kg − 1 ) 61.21 ± 6.74b 113.84 ± 12.43a 85.93 ± 16.65ab 100.28 ± 12.16a PO (mg kg − 1 ) 1007 ± 115b 958 ± 18b 1226 ± 33a 1113 ± 32ab pH 4.43 ± 0.04bc 4.33 ± 0.09c 4.60 ± 0.04a 4.53 ± 0.03ab Soil bulk density(g cm − 3 ) 1.41 ± 0.06a 1.46 ± 0.06a 1.46 ± 0.04a 1.45 ± 0.05a All data are shown as mean ± standard error (n = 9). Values followed by different letters within the same row are significantly different ( P < 0.05). Refer to Table 1 for details of intercropping treatments. SOC: soil organic carbon. TN: soil total nitrogen concentration. TP: soil total phosphorus concentration. PO: Polyphenol oxidase. 3.3 Effects of intercropping on soil erosion and nutrient losses Across the five rainfall events, the reduction in runoff, soil loss, total nitrogen (TN) loss, and TP loss followed a consistent pattern between the intercropping treatments and the control (Fig. 3 ). Data from all rainfall events were combined to illustrate the total reduction in runoff and nutrient loss (Table 3 ). The intercropping treatments reduced total runoff by 33.9 to 51.4% compared with the control, with the reduction being statistically significant. Similarly, intercropping significantly reduced soil loss by 72.4 to 84.3%, TN loss by 34.4 to 56.9%, and TP loss by 48.0 to 60.1% compared to the control (Table 3 ). Table 3 Effects of intercropping on total runoff, soil loss, and nutrient loss of a Camellia oleifera plantation Soil erosion Intercropping treatment Control CO-PT CO-CL CO-MH Total runoff (m 3 ha − 1 ) 38.92 ± 0.51a 25.74 ± 0.38b 21.88 ± 0.6c 18.91 ± 0.23d Total soil loss (kg ha − 1 ) 464 ± 18a 128 ± 5b 73 ± 4c 82 ± 3c Total TN loss (g ha − 1 ) 99.92 ± 2.52a 65.55 ± 1.77b 53.18 ± 2.51c 43.09 ± 1.75d Total TP loss (g ha − 1 ) 20.16 ± 1.16a 9.21 ± 0.63b 8.05 ± 0.57b 10.49 ± 2.03b Values followed by different letters within the same row are significantly different ( P < 0.05). Refer to Table 1 for details of intercropping treatment. TN: total nitrogen content in water; TP: total phosphorus content in water. 3.4 The effects of intercropping on soil microbial diversity and abundance Soil bacterial community Intercropping altered the relative abundance of soil bacterial communities (Fig. 4 a, Table S1). The relative abundance of Chloroflexi decreased by 16.7 to 44.2% in the intercropping treatments compared with the control. In contrast, the CO-CL and CO-MH treatments increased the relative abundance of Acidobacteria by 115.9 and 95.8%, respectively, and the relative abundance of Verrucomicrobia by 820 and 481%, respectively, compared with the controls. Diversity and richness indices (Sobs, Shannon, and Simpson) of the soil bacterial community also varied markedly between the intercropping treatments and the control (Fig. 5 a). Sobs index was lowest in the control, 33.2 to 91.6% lower than that of the three intercropping treatments. Similarly, Shannon index in the control was 14.9% and 11.7% lower than that in the CO-CL and CO-MH , respectively. Simpson index was lowest in the control. Values are percentage changes in relative abundance compared with the control. Only data showing significant changes are presented here. Refer to Table 1 for details of intercropping treatments. Soil fungal community Intercropping influenced the soil fungal community (Fig. 4 b, Table S1). The relative abundance of Chytridiomycota decreased by 96.9 to 99.2% in the intercropping treatments compared with the control (Table S1). In contrast, relative abundance of Glomeromycota in the CO-CL and CO-MH treatments increased by 1063 and 137%, respectively (Table S1,). Diversity and richness indices (Sobs, Shannon, and Simpson) of the soil fungal community varied between the intercropping treatments and the control (Fig. 5 b). Sobs index was lowest in CO-PT , significantly lower than that of the other two intercropping treatments and the control (Table S1). Shannon index was lowest in CO-PT , followed by CO-MH , CO-CL , and the control. Simpson index ranged from 0.87 to 0.94 across the treatments, but the differences were not significant. 4. Discussion 4.1 Reduction in Runoff and Soil Erosion Intercropping Camellia oleifera with Parthenocissus tricuspidata, Coreopsis lanceolata , and Mentha haplocalyx consistently reduced runoff, soil loss, and nutrient loss compared with monoculture controls. Runoff decreased by up to 51.4%, whereas soil loss was reduced by up to 84.3% (Table 3 ). These reductions can be attributed to the combined effects of presence of a ground cover and additionalroot systems, and improved soil structure. The dense foliage of the intercropped species likely served as a living mulch, reducing the kinetic energy of rain and slowing surface water flow, thereby promoting water infiltration. Additionally, the shallow root systems of the intercropped species, in contrast to the deeper roots of C. oleifera , probably created a network that bound soil particles, reducing their susceptibility to erosion. This mechanism aligns with findings from other agricultural systems, such as maize-bean intercropping, where complementary root architectures greatly reduced soil erosion (Li et al., 2007 ). Furthermore, the organic matter from leaf litter and root exudates from intercropped species enhance soil aggregation, stabilizing the soil and further mitigating erosion (Jose, 2009 ; Zhang et al., 2019 ). Our findings align with recent studies on C. oleifera intercropping systems. For example, Duanyuan et al. ( 2023 ) demonstrated that intercropping C. oleifera with Cassia spp. under straw mulching reduced runoff by 28–45% and soil loss by 50–70%, corroborating our results. Similarly, Zheng et al. ( 2024 ) reported that peanut straw mulching in C. oleifera intercropping systems significantly reduced nitrogen loss, mirroring our observed reductions in TN (34.4–56.9%) and TP (48.0–60.1%) losses. These studies collectively highlight the effectiveness of intercropping in mitigating erosion in C. oleifera plantations, though the magnitude of benefits varies with companion species and management practices. 4.2 Improvement in Soil Nutrient Status Intercropping significantly enhanced soil nutrient availability, with the most pronounced effects observed in the CO-CL ( Camellia oleifera–Coreopsis lanceolata ) and CO-PT ( C. oleifera–Pueraria thomsonii ) treatments. Soil organic carbon (SOC) was highest in CO-CL (13.6 g·kg⁻¹), while total phosphorus (TP) and urease activity were highest in CO-PT , increasing by 56.4 and 86.0%, respectively, compared with the monoculture control. Losses of TN and TP were reduced by up to 56.9% and up to 60.1%, respectively, in the intercropping treatments (Table 3 ). These improvements likely resulted from three interrelated processes. First, reduced soil erosion minimizes the loss of TN and TP through runoff. Second, the diverse root systems of C. oleifera and the intercropped species likely accessed nutrients from different soil layers, reducing leaching and improving nutrient-use efficiency. Third, increased microbial activity enhanced the decomposition of organic matter, releasing nutrients in plant-available forms and increasing SOC, TN, and TP stocks (see more details in the microbe section below). These findings are consistent with studies in other agroforestry systems. For example, Zhang et al. ( 2024 ) found that intercropping with legumes increased SOC by 20–40% and TP by 15–30% in Entisol soils, though their reported gains were slightly lower than ours, possibly due to differences in companion species or soil types. Notably, our results contrast with Tan et al. ( 2024 ), who observed minimal changes in TN after transforming low-yield C. oleifera plantations, suggesting that the choice of intercropping species (e.g., nitrogen-fixing vs. non-fixing) critically influences nutrient dynamics. Similarly, intercropping Lycium barbarum with grasses also increased soil TN, and urease activity (Zhu et al., 2022 ). Comparable benefits have been observed in coffee and cocoa agroforestry systems, where intercropping with shade trees or ground-covering plants reduced erosion and improved soil nutrient status (Isaac et al., 2012 ; Siles et al., 2010 ). Despite the reduced losses in TN to soil erosion, soil TN was reduced by 33.5% in the CO-CL treatment compared with the monoculture control (Table 2 ). This unexpected reduction could be attributed to the greater nitrogen uptake by the intercropped species, Coreopsis lanceolata that may have competed with Camellia oleifera for available soil nitrogen, leading to faster depletion of TN. Coreopsis lanceolata is fast-growing and may have absorbed more nitrogen from the soil, reducing overall TN content as has been reported for other intercropping species (Jensen et al., 2015 ). 4.3 Enhancement of Soil Microbial Diversity Intercropping reshaped microbial community structure, with notable shifts in the bacterial and fungal populations. Higher Sobs (richness) and Shannon (diversity) indices of soil bacteria in the intercropping treatments (Fig. 5 ) are indicative of improved nutrient cycling and soil health. For instance, intercropping increased the relative abundance of Acidobacteria and Verrucomicrobia by up to 116% and up to 820%, respectively (Table S1). These increases suggest enhanced nutrient cycling in intercropped systems. Both Acidobacteria and Verrucomicrobia are among the most prevalent soil bacteria in acidic environments and possess extensive carbohydrate-active enzyme systems capable of breaking down complex plant polymers like cellulose and hemicellulose (Bünger et al., 2020 ; Huang et al., 2023 ; Pinto et al., 2020 ). Furthermore, the levels of Acidobacteria have been reported to positively correlate with plant growth through facilitating organic P mineralization and N cycling (Liu et al., 2024 ). In the three intercropped treatments, the relative abundance of Chloroflexi decreased by up to 44.2% (Table S1). While studies have shown Chloroflexi participate in organic matter degradation and nitrogen removal (Bovio-Winkler et al., 2023 ), it is unclear if the reduction in Chloroflexi would have had a negative effect on soil conditions for plant growth. The Sobs and Shannon indices of the soil fungi varied but showed no consistent patterns between the control and the three intercropping treatments (Fig. 5 ). The CO-CL treatment increased the relative abundance of Glomeromycota, a group of fungi that form symbiotic relationships with plant roots and improve nutrient uptake (Bhupenchandra et al., 2024 ; Zhang et al., 2020 ). These changes align with studies showing that diverse root exudates and organic inputs in intercropping systems create a more heterogeneous and nutrient-rich environment for microbial growth (Bais et al., 2006 ; Isaac et al., 2012 ; Van Der Heijden et al., 2008 ). However, the marked decrease in the relative abundance of Chytridiomycota in the intercropping treatment from 3.59–0.03% is interesting. While their role in soil nutrient cycling remains unclear, some Chytridiomycota (eg, Synchytrium endobioticum ) are plant pathogens (Putnam and Hampson, 1989 ). As our analysis cannot identify fungi at the species level, the ecological implications of this reduction remain unclear. 4.4 Improvement in Camellia oleifera Productivity Intercropping greatly enhanced C. oleifera productivity, with CO-PT yielding the highest total fruit production (134% greater than the control) and the highest total oil yield (157 kg ha − 1 ). Although CO-MH had the lowest average fruit weight, it exhibited the highest oil content (8.6%) (Table 1 ), showing that intercropping can improve both yield and quality. The positive correlation between oil content and soil erosion prevention (reduced runoff, soil loss, and TN loss) highlights the importance of soil conservation for C. oleifera productivity. These improvements in productivity are likely driven by the synergistic interactions among the intercropped species that enhance nutrient cycling and soil fertility. In our study, these synergistic effects are evident in significant increases in SOC, TP, and urease activity, particularly in the CO-PT and CO-CL treatments. These findings align with previous studies demonstrating that intercropping systems combining deep- (the crop) and shallow-rooted plants (the herb species) create a more efficient use of soil resources, reducing interspecies competition and enhancing overall system productivity (Brooker et al., 2015 ; Lithourgidis et al., 2011 ). Similarly, intercropping increased productivity by improving soil nutrient status and microbial activity, as reported for Lycium barbarum with grasses (Zhu et al., 2022 ). 5. Conclusions Our study demonstrates that intercropping Camellia oleifera with herbaceous species (Parthenocissus tricuspidata, Coreopsis lanceolata, and Mentha haplocalyx) significantly mitigates soil erosion, enhances soil health, and boosts productivity in subtropical red soils. Key findings include: (1) Erosion control: Intercropping reduced runoff by 33.9–51.4% and soil loss by 72.4–84.3%, primarily through improved ground cover and root-mediated soil stabilization. These results align with global agroforestry studies but highlight the efficacy of non-legume species in erosion-prone red soils. (2) Soil health: Intercropping increased soil organic carbon (7.4–53.8%), phosphorus availability (2.3–56.4%), and urease activity (40.4–86.0%), while reshaping microbial communities toward beneficial taxa (e.g., Acidobacteria, Verrucomicrobia). Such shifts suggest enhanced nutrient cycling and resilience, critical for degraded subtropical soils. (3) Productivity gains: The C. oleifera–P. tricuspidata system achieved the highest fruit yield (134% increase) and oil production (157 kg ha⁻¹), linking soil conservation directly to economic returns. These findings highlight intercropping as a sustainable strategy for C. oleifera plantations in erosion-vulnerable regions. Declarations CRediT authorship contribution statement Zeyao Zhao: Writing – review & editing, Supervision, Methodology, Formal analysis, Data curation, Conceptualization. Lin Chen: Methodology, Investigation, Formal analysis. Wanwan He: Investigation, Data curation. Wenjun Xie: Investigation, Formal analysis. Byron B. Lamont: Writing – review & editing, Methodology, Conceptualization. Long sheng Chen: Investigation, Formal analysis, Methodology, Data curation. Li Mei: Writing – review & editing, Validation, Supervision, Resources, Project administration, Methodology, Funding acquisition, Formal analysis, Conceptualization. Zhaogui Yan: Writing – review & editing, Writing – original draft, Visualization, Validation, Supervision, Resources. Declaration of competing interests In submitting this manuscript, we provide the following statements: (1) No conflict of interest exists in the submission of this manuscript; (2) The manuscript is approved by all authors; (3) The work described was original and has not been published previously, and is not under consideration for publication elsewhere; (4) All the authors listed have made substantial contributions to the research design, or the acquisition, analysis or interpretation of data, or drafting the paper or revising it critically; and (5) Nobody who qualifies for authorship has been excluded. Acknowledgements This study was supported by National Key Research and Development Program of China (2017YFC0505503). We thank the members of the Hubei Engineering Technology Research Center for Forestry Information Laboratory for their invaluable assistance. Data availability Data will be made available on request. 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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-7271330","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":500784317,"identity":"2f4aea25-ee9c-408a-b60a-87937c408ef2","order_by":0,"name":"Zeyao Zhao","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAABA0lEQVRIie3RMUsDMRTA8YRA6vDkHF9Q2s35wUFVKPar5Ch4SyhCF8fArX6AiH4JF+ccwrmIroUudx9AuC7iUKzprL3q5pA/BDLkR3gJY7HYfwzD0rTuj5+KslafI0gS+wtSX4qUPVcTOpUXR8r53YTXrcjY3BwfXMnHEVndLQa3RVNrkpo7I9kcXoGY5+3SbCf8rkpJE0wFvFWNwwWcCCvUzcN2IlAPURPOZG+ap0gLOLNeiv0OIjF/D4Sya2aGhyv9AuR1NwE0m1t05vbCBr3fTRDNLMziU4LwyMpOQLmy6Jxl4PL75mPl+9TbfKU9HydJUbbLDvJT3P7tfCwWi8W+9QVoIVKOk9pqzwAAAABJRU5ErkJggg==","orcid":"https://orcid.org/0000-0002-5230-735X","institution":"Huazhong Agriculture University","correspondingAuthor":true,"prefix":"","firstName":"Zeyao","middleName":"","lastName":"Zhao","suffix":""},{"id":500784318,"identity":"a738b569-e4a4-4d5f-ae68-a1bcc8a12048","order_by":1,"name":"Lin Chen","email":"","orcid":"","institution":"","correspondingAuthor":false,"prefix":"","firstName":"Lin","middleName":"","lastName":"Chen","suffix":""},{"id":500784319,"identity":"35cc4412-c460-4659-9ef2-0046579b3c67","order_by":2,"name":"Wanwan He","email":"","orcid":"","institution":"","correspondingAuthor":false,"prefix":"","firstName":"Wanwan","middleName":"","lastName":"He","suffix":""},{"id":500784320,"identity":"ed366964-d811-4ef9-a4c7-a60e4f3ccdb3","order_by":3,"name":"Wenjun Xie","email":"","orcid":"","institution":"","correspondingAuthor":false,"prefix":"","firstName":"Wenjun","middleName":"","lastName":"Xie","suffix":""},{"id":500784321,"identity":"18f03688-93cc-450a-a26a-4c46633034bd","order_by":4,"name":"Byron B. 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The plot was delineated by PVC hardboard on three sides. On the fourth side (the lower side), a metal drainage ditch was constructed for runoff collection. Runoff from the ditch was piped to a three-tank system. Ten 2 cm diameter diversion holes were drilled in the first and second tanks, with the 10\u003csup\u003eth\u003c/sup\u003e hole used for connecting the first and second tanks and the second and third tanks via PVC piping.\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-7271330/v1/0e80753751be1fa3dd5ad351.png"},{"id":89667465,"identity":"dc471d86-347c-4fdb-9477-03cd0b30c40f","added_by":"auto","created_at":"2025-08-22 12:15:37","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":59670,"visible":true,"origin":"","legend":"\u003cp\u003eCorrelation analysis of soil erosion and fruit production of a \u003cem\u003eCamellia oleifera \u003c/em\u003eplantation\u003cem\u003e.\u003c/em\u003e Lower triangular matrix designates correlation coefficients (Black and blue numbers designate positive and negative correlation coefficients respectively). Upper triangular matrix designates \u003cem\u003eP\u003c/em\u003e value. TN: total nitrogen content in water. TP: total phosphorus content in water.\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-7271330/v1/686a9ff31b4a2ea6b9a6e6a9.png"},{"id":89667471,"identity":"fd19cf10-4a1d-44f8-910f-5b3bd75b87a6","added_by":"auto","created_at":"2025-08-22 12:15:38","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":92339,"visible":true,"origin":"","legend":"\u003cp\u003eThe effects of intercropping on runoff, soil loss, and nutrient loss in a \u003cem\u003eCamellia oleifera\u003c/em\u003eplantation. TN: total nitrogen content in water. TP: total phosphorus content in water. (a) runoff; (b) soil loss; (c) TN loss; (d) TP loss; (e) Rainfall. Numbers above columns are the levels of significance according to Tukey’s test (at \u003cem\u003eP\u003c/em\u003e \u0026lt; 0.05). Refer to Table 1 for details of intercropping treatments.\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-7271330/v1/ad92b9fee09a9f20c4715931.png"},{"id":89667466,"identity":"6c9e5649-3d72-49f1-b018-bc252c1eafa2","added_by":"auto","created_at":"2025-08-22 12:15:37","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":184665,"visible":true,"origin":"","legend":"\u003cp\u003eComposition and relative abundance of top 10 soil microflora in a \u003cem\u003eCamellia oleifera\u003c/em\u003e plantation under three intercropping treatments and control. (a) phylum level of soil bacterial communities; (b) phylum level of soil fungal communities. Refer to Table 1 for details of intercropping treatments.\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-7271330/v1/c110a43d1285608d62fc382a.png"},{"id":89668038,"identity":"24140629-0077-441e-9cc8-f76d6572c578","added_by":"auto","created_at":"2025-08-22 12:23:37","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":48873,"visible":true,"origin":"","legend":"\u003cp\u003eAlpha diversity (Sobs, Shannon, and Simpson indices) of soil bacterial community (a) and fungal community (b) in a \u003cem\u003eCamellia oleifera\u003c/em\u003e plantation subject to intercropping treatments. Different letters above bars designate significant difference between intercropping treatments (\u003cem\u003eP\u003c/em\u003e \u0026lt; 0.05). Refer to Table 1 for details of intercropping treatments.\u003c/p\u003e","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-7271330/v1/dbf825bf0a90d410aa323020.png"},{"id":99172269,"identity":"920bf7cf-51ba-4736-8fc5-35f167f0d47e","added_by":"auto","created_at":"2025-12-29 16:06:48","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1955251,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7271330/v1/72d2db5c-c93c-4017-9613-e8624d538a75.pdf"}],"financialInterests":"","formattedTitle":"\u003cp\u003eIntercropping reduces soil erosion, improves soil conditions, and increases productivity of a \u003cem\u003eCamellia oleifera\u003c/em\u003e plantation\u003c/p\u003e","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003e\u003cem\u003eCamellia oleifera\u003c/em\u003e is a tree species of considerable horticultural importance, valued for its edible oil and ornamental appeal due to its colourful flowers. It is widely cultivated in Europe, North America, and Asia (P\u0026aacute;scoa et al., \u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e2018\u003c/span\u003e; Teixeira and Sousa, \u003cspan citationid=\"CR47\" class=\"CitationRef\"\u003e2021\u003c/span\u003e; Ye et al., \u003cspan citationid=\"CR54\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). In China, \u003cem\u003eC. oleifera\u003c/em\u003e is grown widely for oil production, with plantations reaching 4.9\u0026nbsp;million hectares spread over 15 provinces, including Hunan, Jiangxi, and Guangxi (\u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://www.gov.cn/\u003c/span\u003e\u003cspan address=\"https://www.gov.cn/\" targettype=\"URL\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e). However, many of these plantations, especially those in the red soil regions of the Yangtze River Basin and southern China, suffer from low productivity due to soil quality limitations (Chen et al., \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e2023\u003c/span\u003e; Liu et al., \u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e2017\u003c/span\u003e; Liu et al., \u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e2018\u003c/span\u003e; Tan et al., \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2024\u003c/span\u003e; Tu et al., \u003cspan citationid=\"CR49\" class=\"CitationRef\"\u003e2019\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eRed soils, which dominate subtropical China, are highly susceptible to erosion because of their poor structure, low organic matter content, and susceptibility to compaction (Gao et al., \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e2023\u003c/span\u003e; Zhang et al., \u003cspan citationid=\"CR58\" class=\"CitationRef\"\u003e2004\u003c/span\u003e; Zhang et al., \u003cspan citationid=\"CR61\" class=\"CitationRef\"\u003e2012\u003c/span\u003e). This vulnerability is further exacerbated by the region's hilly terrain and intense summer rainfall, characterized by short, heavy rainstorms (Li et al., \u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e2022\u003c/span\u003e; Li et al., \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e2013\u003c/span\u003e; Yim et al., \u003cspan citationid=\"CR56\" class=\"CitationRef\"\u003e2013\u003c/span\u003e) (\u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttp://www.nmc.cn/\u003c/span\u003e\u003cspan address=\"http://www.nmc.cn/\" targettype=\"URL\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e). The combination of these factors leads to severe soil runoff and nutrient loss, reducing the productivity of \u003cem\u003eC. oleifera\u003c/em\u003e plantations (Chen et al., \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e2023\u003c/span\u003e; Li et al., \u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e2019\u003c/span\u003e; Zhang et al., \u003cspan citationid=\"CR62\" class=\"CitationRef\"\u003e2024\u003c/span\u003e). Addressing these challenges is critical to improving the sustainability and yield of cultivated \u003cem\u003eC. oleifera\u003c/em\u003e in these regions.\u003c/p\u003e\u003cp\u003eIntercropping is the practice of growing several crop species together and is effective for reducing soil erosion by enhancing ground cover and improving soil structure (Brooker et al., \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e2015\u003c/span\u003e; Jensen et al., \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e2015\u003c/span\u003e). It is widely practiced in agricultural cropping systems and to a lesser extent in agroforestry systems. The combined canopy cover protects the soil from the direct impact of raindrops, which is a primary cause of soil particle disintegration and erosion (Liu et al., \u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e2025\u003c/span\u003e). Additionally, the diverse root systems of intercropped plants, such as deep-rooted and shallow-rooted species, stabilize the soil matrix and reduce runoff. For instance, legumes with taproots and cereals with fibrous roots create a network that binds soil particles, minimizing soil erosion (Brooker et al., \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e2015\u003c/span\u003e). This synergistic effect not only preserves topsoil but also maintains soil fertility, making intercropping a sustainable solution for erosion-prone areas.\u003c/p\u003e\u003cp\u003eIntercropping can also enhance crop productivity by optimizing resource use and promoting environmental synergies (Liu et al., \u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e2019\u003c/span\u003e a; Ramirez-Garcia et al., \u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e2015\u003c/span\u003e). The combination of crops with different growth and resource requirements allows for more efficient utilization of sunlight, water, and nutrients (Letourneau et al., \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e2011\u003c/span\u003e; Lithourgidis et al., \u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e2011\u003c/span\u003e). For example, tall crops, such as maize, can provide shade for shade-tolerant species, such as beans, reducing water evaporation and improving microclimatic conditions (Kumari and Choudhary, \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e2022\u003c/span\u003e). These interactions result in higher overall yields compared with monoculture systems, demonstrating the potential of intercropping to increase agricultural productivity while maintaining ecosystem stability.\u003c/p\u003e\u003cp\u003eFurthermore, intercropping fosters a dynamic and resilient soil microbiome (Lu et al., \u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e2023\u003c/span\u003e; Zhao et al., \u003cspan citationid=\"CR64\" class=\"CitationRef\"\u003e2022\u003c/span\u003e). The presence of multiple plant species in intercropping systems leads to the exudation of diverse root secretions, such as sugars, amino acids, and organic acids, that serve as substrates for various microbial populations (Bais et al., \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e2006\u003c/span\u003e). For example, legumes in intercropping systems release flavonoids and other compounds that attract beneficial rhizobacteria and mycorrhizal fungi that play key roles in nutrient cycling and plant health (Hauggaard-Nielsen et al., \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e2009\u003c/span\u003e). In maize-bean intercropping systems, studies have shown increased abundance and activity of nitrogen-fixing bacteria, such as \u003cem\u003eRhizobium\u003c/em\u003e, and phosphate-solubilizing microbes, that enhance nutrient availability for both crops (Li et al., \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e2009\u003c/span\u003e). Moreover, intercropping promotes the coexistence of microbial taxa with complementary functions, such as decomposers, nitrogen fixers, and pathogen suppressors. In cereal-legume intercropping systems, the decomposition of legume residues provides organic matter that supports saprophytic fungi and bacteria, while the cereal roots create a habitat for nitrifying and denitrifying bacteria (Brooker et al., \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e2015\u003c/span\u003e). This functional diversity enhances ecosystem stability and productivity.\u003c/p\u003e\u003cp\u003eTo address soil erosion and low productivity of \u003cem\u003eC. oleifera\u003c/em\u003e plantations, we introduced three plant species, \u003cem\u003eParthenocissus tricuspidata\u003c/em\u003e (\u003cem\u003ePT\u003c/em\u003e), \u003cem\u003eCoreopsis lanceolata\u003c/em\u003e (\u003cem\u003eCL\u003c/em\u003e), and \u003cem\u003eMentha haplocalyx\u003c/em\u003e (\u003cem\u003eMH\u003c/em\u003e), into a \u003cem\u003eC. oleifera\u003c/em\u003e plantation in subtropical Hunan, China. We hypothesized that intercropping would reduce soil erosion, enhance soil nutrients and microbial activity, and increase the productivity of \u003cem\u003eC. oleifera\u003c/em\u003e plantations.\u003c/p\u003e\u003cp\u003eThe three intercropping species were chosen because their ecological and agronomic traits complement those of \u003cem\u003eC. oleifera\u003c/em\u003e, making them ideal for studying the potential benefits of intercropping. \u003cem\u003eParthenocissus tricuspidata\u003c/em\u003e (family Vitaceae) is a fast-growing climbing vine originating in East Asia. It has the ability to quickly cover surfaces, making it an ideal species for preventing soil erosion. Moreover, it can adapt to diverse soil conditions and tolerate shady environments (Wang et al., \u003cspan citationid=\"CR52\" class=\"CitationRef\"\u003e2010\u003c/span\u003e), making it a perfect companion for \u003cem\u003eC. oleifera\u003c/em\u003e plantations.\u003c/p\u003e\u003cp\u003e\u003cem\u003eCoreopsis lanceolata\u003c/em\u003e (family Asteraceae) is a perennial herb native to North America (\u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://plants.usda.gov/\u003c/span\u003e\u003cspan address=\"https://plants.usda.gov/\" targettype=\"URL\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e) and widely distributed in subtropical China. \u003cem\u003eMentha haplocalyx\u003c/em\u003e (family Lamiaceae) is a common aromatic perennial herb in East Asia and is highly valued for its rich essential oil content (An et al., \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2024\u003c/span\u003e). Both species have thick, dense foliage, which helps to retain soil moisture and improve the soil microbial activities, thus promoting the overall health of the intercropped system (Shi et al., \u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e2018\u003c/span\u003e). In addition, both species are known for their ability to grow in dry and infertile soils (Folgate and Scheiner, \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e1992\u003c/span\u003e; Wang et al., \u003cspan citationid=\"CR51\" class=\"CitationRef\"\u003e2009\u003c/span\u003e; Zhou et al., \u003cspan citationid=\"CR66\" class=\"CitationRef\"\u003e2021\u003c/span\u003e), making them highly suitable for intercropping.\u003c/p\u003e\u003cp\u003eOur study had three objectives: (1) to examine how intercropping affects soil physical and chemical properties, as well as soil microbial communities; (2) to evaluate the effectiveness of different intercropping systems in reducing soil erosion and nutrient loss; and (3) to assess the impact of intercropping on \u003cem\u003eC. oleifera\u003c/em\u003e fruit yield and quality. Ultimately, we aimed to determine the most effective intercropping system to minimize soil erosion and improve overall productivity for \u003cem\u003eC. oleifera\u003c/em\u003e plantations in the red soil regions.\u003c/p\u003e"},{"header":"2. Material and methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\u003ch2\u003e2.1 Site description\u003c/h2\u003e\u003cp\u003eThe study was conducted in a \u003cem\u003eCamellia oleifera\u003c/em\u003e plantation in Shaoyang County (26\u0026deg;54\u0026prime;N, 111\u0026deg;22\u0026prime;E), Hunan Province, China. This area has a humid subtropical monsoon climate, with an average annual temperature of 18.3℃ and average annual sunshine of 1610 hours (Liu et al., \u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e2019\u003c/span\u003eb). The soil is mainly red soil developed from Quaternary red clay. Soil depth is usually deeper than 80 cm. Total annual rainfall is 1300 mm with the rainy season from April to June with an average rainfall of 545.4 mm. The dry season is from July to September with an average rainfall of 273.1 mm. Soil erosion is most severe during the rainy season.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec4\" class=\"Section2\"\u003e\u003ch2\u003e2.2 Intercropping treatment\u003c/h2\u003e\u003cp\u003eIn 2014, the intercropping treatment was conducted on a hilly site with a slope of 13\u0026ndash;17 degrees. Leveled planting beds (approximately 1 m wide) were prepared at 3 m intervals. Three-year-old \u003cem\u003eC. oleifera\u003c/em\u003e (CO) seedlings were planted in a monoculture arrangement (3 \u0026times; 3 m spacing) on these beds (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). Compound fertilizer (25% N, 10% P, and 5% K) was applied at 550\u0026ndash;600 kg ha\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e at the time of planting. Weeding was done twice (May and October). In April, 2018, twelve 15 \u0026times; 20 m plots in the \u003cem\u003eC. oleifera\u003c/em\u003e plantation were selected. Plots were spaced at 5 m minimum Distance. Nine of the plots were randomly intercropped with \u003cem\u003eParthenocissus tricuspidata\u003c/em\u003e (\u003cem\u003ePT\u003c/em\u003e), \u003cem\u003eCoreopsis lanceolata\u003c/em\u003e (\u003cem\u003eCL\u003c/em\u003e), and \u003cem\u003eMentha haplocalyx\u003c/em\u003e(\u003cem\u003eMH\u003c/em\u003e). Hereafter, these treatments are referred to as \u003cem\u003eCO-PT\u003c/em\u003e, \u003cem\u003eCO-CL\u003c/em\u003e, and \u003cem\u003eCO-MH\u003c/em\u003e, respectively. The other three plots were used as controls (\u003cem\u003eC. oleifera\u003c/em\u003e monoculture). For the \u003cem\u003eCO-PT\u003c/em\u003e treatment, \u003cem\u003eP. tricuspid\u003c/em\u003eata seedlings were planted at 0.5 \u0026times; 0.75 m. For the \u003cem\u003eCO-C\u003c/em\u003eL treatment, \u003cem\u003eC. lanceolata\u003c/em\u003e seedlings were planted at 0.5 \u0026times; 0.75 m. For the \u003cem\u003eCO-MN\u003c/em\u003e treatment, \u003cem\u003eM. haplocalyx\u003c/em\u003e seedlings were planted at 0.5 \u0026times; 0.75 m.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec5\" class=\"Section2\"\u003e\u003ch2\u003e2.3 Runoff collection system\u003c/h2\u003e\u003cp\u003eTo monitor soil erosion, a run-off collection system was set up within each plot (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). The size of the system was 7 \u0026times; 16 m. The long edge of the system was perpendicular to the contour line and the short edge was horizontal to the contour line. The system was separated from the surrounding area with an impermeable PVC hardboard buried 20 cm deep and 20 cm above ground. A drainage ditch was set up at the lower side of the system. In the system, runoff was piped and stored in the collection tanks (80 \u0026times; 90 cm, diameter \u0026times; height). We used a three-tank setup to account for the overflow of the system (Adimassu et al., \u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e2020\u003c/span\u003e; Huo et al., \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). The first tank was connected directly to the collection ditch with a PVC pipe. There were 10 diversion holes of 2 cm in diameter 60 cm above the bottom of the tank in the tank. One of the holes was connected to the second tank that was placed 50 cm lower than the first tank. The second tank, similar in setup to the first tank was connected to the third tank and was placed 50 cm lower than the second tank. The runoff collection was calculated as\u003cdiv id=\"Equ1\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ1\" name=\"EquationSource\"\u003e\n$$\\:Run\\:off\\left({m}^{3}\\bullet\\:{ℎa}^{-1}\\right)=Tank\\:1+tank\\:2\\times\\:10+tank\\:3\\times\\:100\\left(2\\right)$$\u003c/div\u003e\u003cdiv class=\"EquationNumber\"\u003e1\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003eThe daily rainfall was recorded by a HOBO data logging rain gauge 3 (Onset Computer Corporation, USA) installed in the open area at the study site during June-August 2020. During June-August 2020, there were five rainfall events. Runoff was collected and measured immediately after each rainfall event. The runoff from all three tanks was combined and mixed thoroughly. Three 1-L subsamples were collected and returned to the laboratory for further analysis. In the laboratory, each 1-L subsample was divided into two parts. One part was used to estimate the amount of sediment in the runoff. The resultant suspensions were filtered using Whatman 42 filter paper with a pore size of 2.5 \u0026micro;m. The sediment in the filter paper was oven-dried at 105\u0026deg;C for 24 h and weighed to obtain soil loss data. The other part was used for nutrient analysis. The total N and P concentrations were determined by potassium persulfate oxidation ultraviolet spectrophotometry and potassium persulfate oxidation molybdenum antimony resistance colorimetry (Zhang et al., \u003cspan citationid=\"CR63\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). Soil loss was calculated as per the equations given below:\u003cdiv id=\"Equ2\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ2\" name=\"EquationSource\"\u003e\n$$\\:Soil\\:loss\\left(kg\\:{ℎa}^{-1}\\right)=\\frac{Sediment\\:weigℎt\\left(g\\:{m}^{-3}\\right)\\times\\:Runoff\\left({m}^{-3}{ℎa}^{-1}\\right)}{{10}^{3}}$$\u003c/div\u003e\u003cdiv class=\"EquationNumber\"\u003e2\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003eNutrient loss was calculated as per the equations given below:\u003cdiv id=\"Equ3\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ3\" name=\"EquationSource\"\u003e\n$$\\:Nutrient\\:loss\\left(g\\:{ℎa}^{-1}\\right)=\\frac{Nutrent\\:content\\left(g\\:{m}^{-3}\\right)\\times\\:Runoff\\left({m}^{-3}{ℎa}^{-1}\\right)}{{10}^{3}}$$\u003c/div\u003e\u003cdiv class=\"EquationNumber\"\u003e3\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec6\" class=\"Section2\"\u003e\u003ch2\u003e2.4 Fruit yield and oil content of \u003cem\u003eC. oleifera\u003c/em\u003e\u003c/h2\u003e\u003cp\u003eTo compare the effects of intercropping on seed yield and quality of \u003cem\u003eC. oleifera\u003c/em\u003e, we randomly selected three \u003cem\u003eC. oleifera\u003c/em\u003e trees from each of the treatment plots and collected their fruits in October 2020. In total, 36 samples were collected (4 treatments \u0026times; 3 replicate plots \u0026times; 3 trees per plot). All fruits from each tree were harvested and weighed on-site. Three samples of about 500 g of the fruits from each plot were then brought to the laboratory for fruit trait determination. We first separated the pericarp, seed coat, and kernel and weighed them individually. They were then dried at 100\u0026ndash;105℃ for 72 h or until constant weight was reached to give dry weight. Oil content of the kernel was measured by the Soxhlet extractor method (Ye et al., \u003cspan citationid=\"CR55\" class=\"CitationRef\"\u003e2021\u003c/span\u003e; Yu et al., \u003cspan citationid=\"CR57\" class=\"CitationRef\"\u003e2023\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eThe following equations were used to analyze fruit quality traits (Lu et al. \u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e2022\u003c/span\u003e; Ye et al. \u003cspan citationid=\"CR55\" class=\"CitationRef\"\u003e2021\u003c/span\u003e):\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"No\" id=\"Taba\" border=\"1\"\u003e\u003ccolgroup cols=\"2\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:Total\\:fruit\\:yield\\:\\left(kg\\bullet\\:{ℎa}^{-1}\\right)=\\frac{Total\\:fruit\\:weigℎt\\:per\\:tree\\times\\:1156}{10000}\\)\u003c/span\u003e\u003c/span\u003e\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003e(4)\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:Average\\:fruit\\:weigℎt=\\frac{Tℎe\\:weigℎt\\:of\\:wℎole\\:tℎe\\:tree\\:fruit\\:}{Fruit\\:number}\\)\u003c/span\u003e\u003c/span\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e(5)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:Oil\\:content\\left(\\%\\right)=\\frac{Oil\\:weigℎt}{Fruit\\:weigℎt}\\times\\:100\\%\\)\u003c/span\u003e\u003c/span\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e(6)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:Oil\\:yield\\left(kg\\bullet\\:{ℎa}^{-1}\\right)=Total\\:fruit\\:yield\\:per\\:ℎa\\:\\times\\:Oil\\:content\\)\u003c/span\u003e\u003c/span\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e(7)\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003eThere were 1156 \u003cem\u003eC. oleifera\u003c/em\u003e trees per hectare.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec7\" class=\"Section2\"\u003e\u003ch2\u003e2.5 Soil physical and chemical properties and microbial diversity\u003c/h2\u003e\u003cp\u003eThree replicate soil samples (0\u0026ndash;30 cm) were collected from each treatment plot using a soil drill, totaling 36 samples (4 treatments \u0026times; 3 plots \u0026times; 3 replicate samples). The samples were placed in an ice box before transport to the laboratory. Here, each soil sample was then divided into two parts, one was used for measuring soil urease activity, polyphenol oxidase activity and soil microbial diversity. It was stored at -80\u0026deg;C until used. The other part of the soil sample was used for analysis of SOC, TN and total phosphorus (TP).\u003c/p\u003e\u003cp\u003eSoil urease activity, which measures the extracellular enzyme produced by bacteria and fungi and plant roots, was measured by phenol sodium-sodium hypochlorite colorimetric method (Dom\u0026iacute;nguez et al., \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e2017\u003c/span\u003e). Soil polyphenol oxidase (PO, compounds related to polymerization of phenolic materials) was determined by pyrogallol colorimetric method (Wang et al., \u003cspan citationid=\"CR53\" class=\"CitationRef\"\u003e2022\u003c/span\u003e). Soil microbial diversity (Sobs index for richness and Shannon index for diversity) was measured by the high-throughput sequencing technology (Chaudhary et al., \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). Soil organic matter was measured by the dichromate oxidation method (Bao, \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e2000\u003c/span\u003e). total nitrogen was measured by the Kjeldahl method (Tong and Liu, \u003cspan citationid=\"CR48\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). Total phosphorus was measured by the ascorbic acid method (Bao, \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e2000\u003c/span\u003e). Soil pH was measured using the electrode potential method (Bao, \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e2000\u003c/span\u003e).\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e\u003ch2\u003e2.6 Statistical analyses\u003c/h2\u003e\u003cp\u003eOne-way ANOVAs and Tukey\u0026rsquo;s tests were used to analyze the effect of intercropping on the yield of fruit and oil yield, soil physical and chemical properties, total water loss, total soil loss, total nitrogen and phosphorus loss, soil bacterial and fungal diversity, and abundance. Correlation analysis was used to assess the effects of fruit properties and soil physical and chemical properties, runoff, and soil erosion. Significance was accepted at \u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0,05. All data were analyzed by IBM SPSS statistics software (version 21.0) and Origin Pro 2016 software.\u003c/p\u003e\u003c/div\u003e"},{"header":"3. Results","content":"\u003cdiv id=\"Sec10\" class=\"Section2\"\u003e\n\u003ch2\u003e3.1 The effects of intercropping on fruit and oil yield\u003c/h2\u003e\n\u003cp\u003eTotal fruit and oil yield varied significantly between the intercropping treatments and control (Table\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e). The \u003cem\u003eCO-PT\u003c/em\u003e treatment produced the highest total fruit yield, which was 134% higher than that of the control (\u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.05). In contrast, the \u003cem\u003eCO-MH\u003c/em\u003e treatment had the lowest average fruit weight (14.4 g), significantly lower than the other two intercropping treatments and the control (19.9 to 28.0 g). However, oil content was significantly higher in \u003cem\u003eCO-MH\u003c/em\u003e (8.6%) than the other intercropping treatments and the control (5.8 to 6.7%). The total oil yield was highest in \u003cem\u003eCO-PT\u003c/em\u003e (157 kg ha\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e), which was significantly higher than that of the control and the \u003cem\u003eCO-MH\u003c/em\u003e treatment.\u003c/p\u003e\n\u003cp\u003eOil content was negatively correlated with the three erosion-related indices: runoff, soil loss, and TN loss (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e). Additionally, oil content (percentage of oil in the fruit) showed a negative correlation with total fruit yield and soil total phosphorus (TP) loss, though these correlations were only marginally significant (\u003cem\u003eP\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.07 and \u003cem\u003eP\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.09, respectively).\u003c/p\u003e\n\u003cdiv class=\"gridtable\"\u003e\n\u003cdiv class=\"colspec\" align=\"left\"\u003e\u0026nbsp;\u003c/div\u003e\n\u003ctable id=\"Tab1\" border=\"1\"\u003e\u003ccaption\u003e\n\u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e\n\u003cdiv class=\"CaptionContent\"\u003e\n\u003cp\u003eEffects of intercropping on fruit and oil yield of a \u003cem\u003eCamellia oleifera\u003c/em\u003e plantation\u003c/p\u003e\n\u003c/div\u003e\n\u003c/caption\u003e\n\u003cthead\u003e\n\u003ctr\u003e\n\u003cth rowspan=\"2\" align=\"left\"\u003e\n\u003cp\u003eFruit and oil production\u003c/p\u003e\n\u003c/th\u003e\n\u003cth colspan=\"4\" align=\"left\"\u003e\n\u003cp\u003eIntercropping treatment\u003c/p\u003e\n\u003c/th\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eControl\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003e\u003cem\u003eCO-PT\u003c/em\u003e\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003e\u003cem\u003eCO-CL\u003c/em\u003e\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003e\u003cem\u003eCO-MH\u003c/em\u003e\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\u003eTotal fruit yield (kg ha\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1093\u0026thinsp;\u003cem\u003e\u0026plusmn;\u003c/em\u003e\u0026thinsp;263b\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e2554\u0026thinsp;\u003cem\u003e\u0026plusmn;\u003c/em\u003e\u0026thinsp;678a\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1642\u0026thinsp;\u003cem\u003e\u0026plusmn;\u003c/em\u003e\u0026thinsp;277ab\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1003\u0026thinsp;\u003cem\u003e\u0026plusmn;\u003c/em\u003e\u0026thinsp;192b\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eAverage fruit weight (g)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e19.86\u0026thinsp;\u003cem\u003e\u0026plusmn;\u003c/em\u003e\u0026thinsp;2.63ab\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e26.34\u0026thinsp;\u003cem\u003e\u0026plusmn;\u003c/em\u003e\u0026thinsp;4.73a\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e27.96\u0026thinsp;\u003cem\u003e\u0026plusmn;\u003c/em\u003e\u0026thinsp;3.7a\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e14.37\u0026thinsp;\u003cem\u003e\u0026plusmn;\u003c/em\u003e\u0026thinsp;2.09b\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eOil content (%)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e5.76\u0026thinsp;\u003cem\u003e\u0026plusmn;\u003c/em\u003e\u0026thinsp;0.34b\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e6.72\u0026thinsp;\u003cem\u003e\u0026plusmn;\u003c/em\u003e\u0026thinsp;0.44b\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e6.40\u0026thinsp;\u003cem\u003e\u0026plusmn;\u003c/em\u003e\u0026thinsp;0.29b\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e8.64\u0026thinsp;\u003cem\u003e\u0026plusmn;\u003c/em\u003e\u0026thinsp;0.67a\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eTotal oil yield (kg ha\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e64.22\u0026thinsp;\u003cem\u003e\u0026plusmn;\u003c/em\u003e\u0026thinsp;15.74b\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e156.89\u0026thinsp;\u003cem\u003e\u0026plusmn;\u003c/em\u003e\u0026thinsp;34.64a\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e100.77\u0026thinsp;\u003cem\u003e\u0026plusmn;\u003c/em\u003e\u0026thinsp;13.95ab\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e84.23\u0026thinsp;\u003cem\u003e\u0026plusmn;\u003c/em\u003e\u0026thinsp;15.35b\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\u003eAll data are shown as mean\u0026plusmn; standard error (n\u0026thinsp;=\u0026thinsp;9). Different letters in the same row represent significant differences (\u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.05) by Tukey\u0026rsquo;s test. Intercropping treatment: Control: \u003cem\u003eC. oleifera\u003c/em\u003e monoculture, \u003cem\u003eCO-PT: C. oleifera\u003c/em\u003e\u0026thinsp;+\u0026thinsp;\u003cem\u003eParthenocissus tricuspidata\u003c/em\u003e, \u003cem\u003eCO-CL\u003c/em\u003e: \u003cem\u003eC. oleifera\u003c/em\u003e\u0026thinsp;+\u0026thinsp;\u003cem\u003eCoreopsis lanceolata\u003c/em\u003e, \u003cem\u003eCO-MH\u003c/em\u003e: \u003cem\u003eC. oleifera\u003c/em\u003e\u0026thinsp;+\u0026thinsp;\u003cem\u003eMentha haplocalyx\u003c/em\u003e.\u003c/p\u003e\n\u003cp\u003e\u0026nbsp;\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec11\" class=\"Section2\"\u003e\n\u003ch2\u003e3.2 The effects of intercropping on soil chemical and physical properties\u003c/h2\u003e\n\u003cp\u003eIntercropping strongly influenced soil chemical and physical properties (Table\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e). Compared with the control, intercropping increased soil organic carbon (SOC) by 7.4 to 53. 8%, TP by 2.3 to 56.4%, and soil urease activity by 40.4 to 86.0%. Intercropping also increased soil polyphenol oxidase (PO) content by 21.8% and 10.5% in \u003cem\u003eCO-CL\u003c/em\u003e and \u003cem\u003eCO-MH\u003c/em\u003e treatments, respectively, compared with the control, wheeas no significant change was observed in the \u003cem\u003eCO-PT\u003c/em\u003e treatment. In contrast, intercropping decreased soil total nitrogen (TN) by 9.5 to 33.5%. Soil pH in the control was similar to that of \u003cem\u003eCO-PT\u003c/em\u003e but lower than that of \u003cem\u003eCO-CL\u003c/em\u003e and \u003cem\u003eCO-MH\u003c/em\u003e, but, soil bulk density showed little variation between the intercropping treatments and the control (Table\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e).\u003c/p\u003e\n\u003cdiv class=\"gridtable\"\u003e\n\u003cdiv class=\"colspec\" align=\"left\"\u003e\u0026nbsp;\u003c/div\u003e\n\u003ctable id=\"Tab2\" border=\"1\"\u003e\u003ccaption\u003e\n\u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e\n\u003cdiv class=\"CaptionContent\"\u003e\n\u003cp\u003eEffects of intercropping treatments on soil properties of a \u003cem\u003eCamellia oleifera\u003c/em\u003e plantation\u003c/p\u003e\n\u003c/div\u003e\n\u003c/caption\u003e\n\u003cthead\u003e\n\u003ctr\u003e\n\u003cth rowspan=\"2\" align=\"left\"\u003e\n\u003cp\u003eSoil properties\u003c/p\u003e\n\u003c/th\u003e\n\u003cth colspan=\"4\" align=\"left\"\u003e\n\u003cp\u003eIntercropping treatment\u003c/p\u003e\n\u003c/th\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eControl\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003e\u003cem\u003eCO-PT\u003c/em\u003e\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003e\u003cem\u003eCO-CL\u003c/em\u003e\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003e\u003cem\u003eCO-MH\u003c/em\u003e\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\u003eSOC (g kg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e8.87\u0026thinsp;\u003cem\u003e\u0026plusmn;\u003c/em\u003e\u0026thinsp;0.99b\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e9.53\u0026thinsp;\u003cem\u003e\u0026plusmn;\u003c/em\u003e\u0026thinsp;0.83b\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e13.64\u0026thinsp;\u003cem\u003e\u0026plusmn;\u003c/em\u003e\u0026thinsp;0.76a\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e13.09\u0026thinsp;\u003cem\u003e\u0026plusmn;\u003c/em\u003e\u0026thinsp;0.83a\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eTN (g kg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1.58\u0026thinsp;\u003cem\u003e\u0026plusmn;\u003c/em\u003e\u0026thinsp;0.17a\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1.31\u0026thinsp;\u003cem\u003e\u0026plusmn;\u003c/em\u003e\u0026thinsp;0.09ab\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1.05\u0026thinsp;\u003cem\u003e\u0026plusmn;\u003c/em\u003e\u0026thinsp;0.1b\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1.43\u0026thinsp;\u003cem\u003e\u0026plusmn;\u003c/em\u003e\u0026thinsp;0.13a\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eTP (mg kg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e397\u0026thinsp;\u003cem\u003e\u0026plusmn;\u003c/em\u003e\u0026thinsp;48b\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e621\u0026thinsp;\u003cem\u003e\u0026plusmn;\u003c/em\u003e\u0026thinsp;108a\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e545\u0026thinsp;\u003cem\u003e\u0026plusmn;\u003c/em\u003e\u0026thinsp;17ab\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e406\u0026thinsp;\u003cem\u003e\u0026plusmn;\u003c/em\u003e\u0026thinsp;62b\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eUrease (mg kg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e61.21\u0026thinsp;\u003cem\u003e\u0026plusmn;\u003c/em\u003e\u0026thinsp;6.74b\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e113.84\u0026thinsp;\u003cem\u003e\u0026plusmn;\u003c/em\u003e\u0026thinsp;12.43a\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e85.93\u0026thinsp;\u003cem\u003e\u0026plusmn;\u003c/em\u003e\u0026thinsp;16.65ab\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e100.28\u0026thinsp;\u003cem\u003e\u0026plusmn;\u003c/em\u003e\u0026thinsp;12.16a\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003ePO (mg kg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1007\u0026thinsp;\u003cem\u003e\u0026plusmn;\u003c/em\u003e\u0026thinsp;115b\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e958\u0026thinsp;\u003cem\u003e\u0026plusmn;\u003c/em\u003e\u0026thinsp;18b\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1226\u0026thinsp;\u003cem\u003e\u0026plusmn;\u003c/em\u003e\u0026thinsp;33a\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1113\u0026thinsp;\u003cem\u003e\u0026plusmn;\u003c/em\u003e\u0026thinsp;32ab\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=\"left\"\u003e\n\u003cp\u003e4.43\u0026thinsp;\u003cem\u003e\u0026plusmn;\u003c/em\u003e\u0026thinsp;0.04bc\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e4.33\u0026thinsp;\u003cem\u003e\u0026plusmn;\u003c/em\u003e\u0026thinsp;0.09c\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e4.60\u0026thinsp;\u003cem\u003e\u0026plusmn;\u003c/em\u003e\u0026thinsp;0.04a\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e4.53\u0026thinsp;\u003cem\u003e\u0026plusmn;\u003c/em\u003e\u0026thinsp;0.03ab\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eSoil bulk density(g cm\u003csup\u003e\u0026minus;\u0026thinsp;3\u003c/sup\u003e)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1.41\u0026thinsp;\u003cem\u003e\u0026plusmn;\u003c/em\u003e\u0026thinsp;0.06a\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1.46\u0026thinsp;\u003cem\u003e\u0026plusmn;\u003c/em\u003e\u0026thinsp;0.06a\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1.46\u0026thinsp;\u003cem\u003e\u0026plusmn;\u003c/em\u003e\u0026thinsp;0.04a\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e1.45\u0026thinsp;\u003cem\u003e\u0026plusmn;\u003c/em\u003e\u0026thinsp;0.05a\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\u003eAll data are shown as mean\u0026thinsp;\u003cem\u003e\u0026plusmn;\u003c/em\u003e\u0026thinsp;standard error (n\u0026thinsp;=\u0026thinsp;9). Values followed by different letters within the same row are significantly different (\u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.05). Refer to Table\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e for details of intercropping treatments. SOC: soil organic carbon. TN: soil total nitrogen concentration. TP: soil total phosphorus concentration. PO: Polyphenol oxidase.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec12\" class=\"Section2\"\u003e\n\u003ch2\u003e3.3 Effects of intercropping on soil erosion and nutrient losses\u003c/h2\u003e\n\u003cp\u003eAcross the five rainfall events, the reduction in runoff, soil loss, total nitrogen (TN) loss, and TP loss followed a consistent pattern between the intercropping treatments and the control (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003e). Data from all rainfall events were combined to illustrate the total reduction in runoff and nutrient loss (Table\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003e). The intercropping treatments reduced total runoff by 33.9 to 51.4% compared with the control, with the reduction being statistically significant. Similarly, intercropping significantly reduced soil loss by 72.4 to 84.3%, TN loss by 34.4 to 56.9%, and TP loss by 48.0 to 60.1% compared to the control (Table\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003e).\u003c/p\u003e\n\u003cp\u003e\u0026nbsp;\u003c/p\u003e\n\u003cdiv class=\"gridtable\"\u003e\n\u003cdiv class=\"colspec\" align=\"left\"\u003e\u0026nbsp;\u003c/div\u003e\n\u003cdiv class=\"colspec\" align=\"left\"\u003e\u0026nbsp;\u003c/div\u003e\n\u003cdiv class=\"colspec\" align=\"left\"\u003e\u0026nbsp;\u003c/div\u003e\n\u003cdiv class=\"colspec\" align=\"left\"\u003e\u0026nbsp;\u003c/div\u003e\n\u003cdiv class=\"colspec\" align=\"left\"\u003e\u0026nbsp;\u003c/div\u003e\n\u003ctable id=\"Tab3\" border=\"1\"\u003e\u003ccaption\u003e\n\u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e\n\u003cdiv class=\"CaptionContent\"\u003e\n\u003cp\u003eEffects of intercropping on total runoff, soil loss, and nutrient loss of a \u003cem\u003eCamellia oleifera\u003c/em\u003e plantation\u003c/p\u003e\n\u003c/div\u003e\n\u003c/caption\u003e\n\u003cthead\u003e\n\u003ctr\u003e\n\u003cth rowspan=\"2\" align=\"left\"\u003e\n\u003cp\u003eSoil erosion\u003c/p\u003e\n\u003c/th\u003e\n\u003cth colspan=\"4\" align=\"left\"\u003e\n\u003cp\u003eIntercropping treatment\u003c/p\u003e\n\u003c/th\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003eControl\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003e\u003cem\u003eCO-PT\u003c/em\u003e\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003e\u003cem\u003eCO-CL\u003c/em\u003e\u003c/p\u003e\n\u003c/th\u003e\n\u003cth align=\"left\"\u003e\n\u003cp\u003e\u003cem\u003eCO-MH\u003c/em\u003e\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\u003eTotal runoff\u003c/p\u003e\n\u003cp\u003e(m\u003csup\u003e3\u003c/sup\u003e ha\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e38.92\u0026thinsp;\u003cem\u003e\u0026plusmn;\u003c/em\u003e\u0026thinsp;0.51a\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e25.74\u0026thinsp;\u003cem\u003e\u0026plusmn;\u003c/em\u003e\u0026thinsp;0.38b\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e21.88\u0026thinsp;\u003cem\u003e\u0026plusmn;\u003c/em\u003e\u0026thinsp;0.6c\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e18.91\u0026thinsp;\u003cem\u003e\u0026plusmn;\u003c/em\u003e\u0026thinsp;0.23d\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eTotal soil loss\u003c/p\u003e\n\u003cp\u003e(kg ha\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e464\u0026thinsp;\u003cem\u003e\u0026plusmn;\u003c/em\u003e\u0026thinsp;18a\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e128\u0026thinsp;\u003cem\u003e\u0026plusmn;\u003c/em\u003e\u0026thinsp;5b\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e73\u0026thinsp;\u003cem\u003e\u0026plusmn;\u003c/em\u003e\u0026thinsp;4c\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e82\u0026thinsp;\u003cem\u003e\u0026plusmn;\u003c/em\u003e\u0026thinsp;3c\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eTotal TN loss\u003c/p\u003e\n\u003cp\u003e(g ha\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e99.92\u0026thinsp;\u003cem\u003e\u0026plusmn;\u003c/em\u003e\u0026thinsp;2.52a\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e65.55\u0026thinsp;\u003cem\u003e\u0026plusmn;\u003c/em\u003e\u0026thinsp;1.77b\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e53.18\u0026thinsp;\u003cem\u003e\u0026plusmn;\u003c/em\u003e\u0026thinsp;2.51c\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e43.09\u0026thinsp;\u003cem\u003e\u0026plusmn;\u003c/em\u003e\u0026thinsp;1.75d\u003c/p\u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003eTotal TP loss\u003c/p\u003e\n\u003cp\u003e(g ha\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e)\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e20.16\u0026thinsp;\u003cem\u003e\u0026plusmn;\u003c/em\u003e\u0026thinsp;1.16a\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e9.21\u0026thinsp;\u003cem\u003e\u0026plusmn;\u003c/em\u003e\u0026thinsp;0.63b\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e8.05\u0026thinsp;\u003cem\u003e\u0026plusmn;\u003c/em\u003e\u0026thinsp;0.57b\u003c/p\u003e\n\u003c/td\u003e\n\u003ctd align=\"left\"\u003e\n\u003cp\u003e10.49\u0026thinsp;\u003cem\u003e\u0026plusmn;\u003c/em\u003e\u0026thinsp;2.03b\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\u003eValues followed by different letters within the same row are significantly different\u003c/p\u003e\n\u003cp\u003e(\u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.05). Refer to Table\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e for details of intercropping treatment. TN: total nitrogen content in water; TP: total phosphorus content in water.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec13\" class=\"Section2\"\u003e\n\u003ch2\u003e3.4 The effects of intercropping on soil microbial diversity and abundance\u003c/h2\u003e\n\u003cp\u003eSoil bacterial community\u003c/p\u003e\n\u003cp\u003eIntercropping altered the relative abundance of soil bacterial communities (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003ea, Table S1). The relative abundance of Chloroflexi decreased by 16.7 to 44.2% in the intercropping treatments compared with the control. In contrast, the \u003cem\u003eCO-CL\u003c/em\u003e and \u003cem\u003eCO-MH\u003c/em\u003e treatments increased the relative abundance of Acidobacteria by 115.9 and 95.8%, respectively, and the relative abundance of Verrucomicrobia by 820 and 481%, respectively, compared with the controls.\u003c/p\u003e\n\u003cp\u003eDiversity and richness indices (Sobs, Shannon, and Simpson) of the soil bacterial community also varied markedly between the intercropping treatments and the control (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e5\u003c/span\u003ea). Sobs index was lowest in the control, 33.2 to 91.6% lower than that of the three intercropping treatments. Similarly, Shannon index in the control was 14.9% and 11.7% lower than that in the \u003cem\u003eCO-CL\u003c/em\u003e and \u003cem\u003eCO-MH\u003c/em\u003e, respectively. Simpson index was lowest in the control.\u003c/p\u003e\n\u003cp\u003e\u0026nbsp;\u003c/p\u003e\n\u003cdiv class=\"gridtable\"\u003e\u0026nbsp;\u003c/div\u003e\n\u003cp\u003eValues are percentage changes in relative abundance compared with the control. Only data showing significant changes are presented here. Refer to Table\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e for details of intercropping treatments.\u003c/p\u003e\n\u003cp\u003eSoil fungal community\u003c/p\u003e\n\u003cp\u003eIntercropping influenced the soil fungal community (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003eb, Table S1). The relative abundance of Chytridiomycota decreased by 96.9 to 99.2% in the intercropping treatments compared with the control (Table S1). In contrast, relative abundance of Glomeromycota in the \u003cem\u003eCO-CL\u003c/em\u003e and \u003cem\u003eCO-MH\u003c/em\u003e treatments increased by 1063 and 137%, respectively (Table S1,). Diversity and richness indices (Sobs, Shannon, and Simpson) of the soil fungal community varied between the intercropping treatments and the control (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e5\u003c/span\u003eb). Sobs index was lowest in \u003cem\u003eCO-PT\u003c/em\u003e, significantly lower than that of the other two intercropping treatments and the control (Table S1). Shannon index was lowest in \u003cem\u003eCO-PT\u003c/em\u003e, followed by \u003cem\u003eCO-MH\u003c/em\u003e, \u003cem\u003eCO-CL\u003c/em\u003e, and the control. Simpson index ranged from 0.87 to 0.94 across the treatments, but the differences were not significant.\u003c/p\u003e\n\u003c/div\u003e"},{"header":"4. Discussion","content":"\u003cdiv id=\"Sec15\" class=\"Section2\"\u003e\u003ch2\u003e4.1 Reduction in Runoff and Soil Erosion\u003c/h2\u003e\u003cp\u003eIntercropping \u003cem\u003eCamellia oleifera\u003c/em\u003e with \u003cem\u003eParthenocissus tricuspidata, Coreopsis lanceolata\u003c/em\u003e, and \u003cem\u003eMentha haplocalyx\u003c/em\u003e consistently reduced runoff, soil loss, and nutrient loss compared with monoculture controls. Runoff decreased by up to 51.4%, whereas soil loss was reduced by up to 84.3% (Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e). These reductions can be attributed to the combined effects of presence of a ground cover and additionalroot systems, and improved soil structure. The dense foliage of the intercropped species likely served as a living mulch, reducing the kinetic energy of rain and slowing surface water flow, thereby promoting water infiltration. Additionally, the shallow root systems of the intercropped species, in contrast to the deeper roots of \u003cem\u003eC. oleifera\u003c/em\u003e, probably created a network that bound soil particles, reducing their susceptibility to erosion. This mechanism aligns with findings from other agricultural systems, such as maize-bean intercropping, where complementary root architectures greatly reduced soil erosion (Li et al., \u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e2007\u003c/span\u003e). Furthermore, the organic matter from leaf litter and root exudates from intercropped species enhance soil aggregation, stabilizing the soil and further mitigating erosion (Jose, \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e2009\u003c/span\u003e; Zhang et al., \u003cspan citationid=\"CR60\" class=\"CitationRef\"\u003e2019\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eOur findings align with recent studies on \u003cem\u003eC. oleifera\u003c/em\u003e intercropping systems. For example, Duanyuan et al. (\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e2023\u003c/span\u003e) demonstrated that intercropping \u003cem\u003eC. oleifera\u003c/em\u003e with \u003cem\u003eCassia\u003c/em\u003e spp. under straw mulching reduced runoff by 28\u0026ndash;45% and soil loss by 50\u0026ndash;70%, corroborating our results. Similarly, Zheng et al. (\u003cspan citationid=\"CR65\" class=\"CitationRef\"\u003e2024\u003c/span\u003e) reported that peanut straw mulching in \u003cem\u003eC. oleifera\u003c/em\u003e intercropping systems significantly reduced nitrogen loss, mirroring our observed reductions in TN (34.4\u0026ndash;56.9%) and TP (48.0\u0026ndash;60.1%) losses. These studies collectively highlight the effectiveness of intercropping in mitigating erosion in \u003cem\u003eC. oleifera\u003c/em\u003e plantations, though the magnitude of benefits varies with companion species and management practices.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec16\" class=\"Section2\"\u003e\u003ch2\u003e4.2 Improvement in Soil Nutrient Status\u003c/h2\u003e\u003cp\u003eIntercropping significantly enhanced soil nutrient availability, with the most pronounced effects observed in the \u003cem\u003eCO-CL\u003c/em\u003e (\u003cem\u003eCamellia oleifera\u0026ndash;Coreopsis lanceolata\u003c/em\u003e) and \u003cem\u003eCO-PT\u003c/em\u003e (\u003cem\u003eC. oleifera\u0026ndash;Pueraria thomsonii\u003c/em\u003e) treatments. Soil organic carbon (SOC) was highest in \u003cem\u003eCO-CL\u003c/em\u003e (13.6 g\u0026middot;kg⁻\u0026sup1;), while total phosphorus (TP) and urease activity were highest in \u003cem\u003eCO-PT\u003c/em\u003e, increasing by 56.4 and 86.0%, respectively, compared with the monoculture control.\u003c/p\u003e\u003cp\u003eLosses of TN and TP were reduced by up to 56.9% and up to 60.1%, respectively, in the intercropping treatments (Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e). These improvements likely resulted from three interrelated processes. First, reduced soil erosion minimizes the loss of TN and TP through runoff. Second, the diverse root systems of \u003cem\u003eC. oleifera\u003c/em\u003e and the intercropped species likely accessed nutrients from different soil layers, reducing leaching and improving nutrient-use efficiency. Third, increased microbial activity enhanced the decomposition of organic matter, releasing nutrients in plant-available forms and increasing SOC, TN, and TP stocks (see more details in the microbe section below).\u003c/p\u003e\u003cp\u003eThese findings are consistent with studies in other agroforestry systems. For example, Zhang et al. (\u003cspan citationid=\"CR62\" class=\"CitationRef\"\u003e2024\u003c/span\u003e) found that intercropping with legumes increased SOC by 20\u0026ndash;40% and TP by 15\u0026ndash;30% in Entisol soils, though their reported gains were slightly lower than ours, possibly due to differences in companion species or soil types. Notably, our results contrast with Tan et al. (\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2024\u003c/span\u003e), who observed minimal changes in TN after transforming low-yield \u003cem\u003eC. oleifera\u003c/em\u003e plantations, suggesting that the choice of intercropping species (e.g., nitrogen-fixing vs. non-fixing) critically influences nutrient dynamics. Similarly, intercropping \u003cem\u003eLycium barbarum\u003c/em\u003e with grasses also increased soil TN, and urease activity (Zhu et al., \u003cspan citationid=\"CR67\" class=\"CitationRef\"\u003e2022\u003c/span\u003e). Comparable benefits have been observed in coffee and cocoa agroforestry systems, where intercropping with shade trees or ground-covering plants reduced erosion and improved soil nutrient status (Isaac et al., \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e2012\u003c/span\u003e; Siles et al., \u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e2010\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eDespite the reduced losses in TN to soil erosion, soil TN was reduced by 33.5% in the \u003cem\u003eCO-CL\u003c/em\u003e treatment compared with the monoculture control (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). This unexpected reduction could be attributed to the greater nitrogen uptake by the intercropped species, \u003cem\u003eCoreopsis lanceolata\u003c/em\u003e that may have competed with \u003cem\u003eCamellia oleifera\u003c/em\u003e for available soil nitrogen, leading to faster depletion of TN. \u003cem\u003eCoreopsis lanceolata\u003c/em\u003e is fast-growing and may have absorbed more nitrogen from the soil, reducing overall TN content as has been reported for other intercropping species (Jensen et al., \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e2015\u003c/span\u003e).\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec17\" class=\"Section2\"\u003e\u003ch2\u003e4.3 Enhancement of Soil Microbial Diversity\u003c/h2\u003e\u003cp\u003eIntercropping reshaped microbial community structure, with notable shifts in the bacterial and fungal populations. Higher Sobs (richness) and Shannon (diversity) indices of soil bacteria in the intercropping treatments (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e) are indicative of improved nutrient cycling and soil health. For instance, intercropping increased the relative abundance of Acidobacteria and Verrucomicrobia by up to 116% and up to 820%, respectively (Table S1). These increases suggest enhanced nutrient cycling in intercropped systems. Both Acidobacteria and Verrucomicrobia are among the most prevalent soil bacteria in acidic environments and possess extensive carbohydrate-active enzyme systems capable of breaking down complex plant polymers like cellulose and hemicellulose (B\u0026uuml;nger et al., \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e2020\u003c/span\u003e; Huang et al., \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e2023\u003c/span\u003e; Pinto et al., \u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). Furthermore, the levels of Acidobacteria have been reported to positively correlate with plant growth through facilitating organic P mineralization and N cycling (Liu et al., \u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e2024\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eIn the three intercropped treatments, the relative abundance of Chloroflexi decreased by up to 44.2% (Table S1). While studies have shown Chloroflexi participate in organic matter degradation and nitrogen removal (Bovio-Winkler et al., \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e2023\u003c/span\u003e), it is unclear if the reduction in Chloroflexi would have had a negative effect on soil conditions for plant growth.\u003c/p\u003e\u003cp\u003eThe Sobs and Shannon indices of the soil fungi varied but showed no consistent patterns between the control and the three intercropping treatments (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e). The \u003cem\u003eCO-CL\u003c/em\u003e treatment increased the relative abundance of Glomeromycota, a group of fungi that form symbiotic relationships with plant roots and improve nutrient uptake (Bhupenchandra et al., \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e2024\u003c/span\u003e; Zhang et al., \u003cspan citationid=\"CR59\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). These changes align with studies showing that diverse root exudates and organic inputs in intercropping systems create a more heterogeneous and nutrient-rich environment for microbial growth (Bais et al., \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e2006\u003c/span\u003e; Isaac et al., \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e2012\u003c/span\u003e; Van Der Heijden et al., \u003cspan citationid=\"CR50\" class=\"CitationRef\"\u003e2008\u003c/span\u003e). However, the marked decrease in the relative abundance of Chytridiomycota in the intercropping treatment from 3.59\u0026ndash;0.03% is interesting. While their role in soil nutrient cycling remains unclear, some Chytridiomycota (eg, \u003cem\u003eSynchytrium endobioticum\u003c/em\u003e) are plant pathogens (Putnam and Hampson, \u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e1989\u003c/span\u003e). As our analysis cannot identify fungi at the species level, the ecological implications of this reduction remain unclear.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec18\" class=\"Section2\"\u003e\u003ch2\u003e4.4 Improvement in \u003cem\u003eCamellia oleifera\u003c/em\u003e Productivity\u003c/h2\u003e\u003cp\u003eIntercropping greatly enhanced \u003cem\u003eC. oleifera\u003c/em\u003e productivity, with \u003cem\u003eCO-PT\u003c/em\u003e yielding the highest total fruit production (134% greater than the control) and the highest total oil yield (157 kg ha\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e). Although \u003cem\u003eCO-MH\u003c/em\u003e had the lowest average fruit weight, it exhibited the highest oil content (8.6%) (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e), showing that intercropping can improve both yield and quality. The positive correlation between oil content and soil erosion prevention (reduced runoff, soil loss, and TN loss) highlights the importance of soil conservation for \u003cem\u003eC. oleifera\u003c/em\u003e productivity.\u003c/p\u003e\u003cp\u003eThese improvements in productivity are likely driven by the synergistic interactions among the intercropped species that enhance nutrient cycling and soil fertility. In our study, these synergistic effects are evident in significant increases in SOC, TP, and urease activity, particularly in the \u003cem\u003eCO-PT\u003c/em\u003e and \u003cem\u003eCO-CL\u003c/em\u003e treatments. These findings align with previous studies demonstrating that intercropping systems combining deep- (the crop) and shallow-rooted plants (the herb species) create a more efficient use of soil resources, reducing interspecies competition and enhancing overall system productivity (Brooker et al., \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e2015\u003c/span\u003e; Lithourgidis et al., \u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e2011\u003c/span\u003e). Similarly, intercropping increased productivity by improving soil nutrient status and microbial activity, as reported for \u003cem\u003eLycium barbarum\u003c/em\u003e with grasses (Zhu et al., \u003cspan citationid=\"CR67\" class=\"CitationRef\"\u003e2022\u003c/span\u003e).\u003c/p\u003e\u003c/div\u003e"},{"header":"5. Conclusions","content":"\u003cp\u003eOur study demonstrates that intercropping \u003cem\u003eCamellia oleifera\u003c/em\u003e with herbaceous species (Parthenocissus tricuspidata, Coreopsis lanceolata, and Mentha haplocalyx) significantly mitigates soil erosion, enhances soil health, and boosts productivity in subtropical red soils. Key findings include: (1) Erosion control: Intercropping reduced runoff by 33.9\u0026ndash;51.4% and soil loss by 72.4\u0026ndash;84.3%, primarily through improved ground cover and root-mediated soil stabilization. These results align with global agroforestry studies but highlight the efficacy of non-legume species in erosion-prone red soils. (2) Soil health: Intercropping increased soil organic carbon (7.4\u0026ndash;53.8%), phosphorus availability (2.3\u0026ndash;56.4%), and urease activity (40.4\u0026ndash;86.0%), while reshaping microbial communities toward beneficial taxa (e.g., Acidobacteria, Verrucomicrobia). Such shifts suggest enhanced nutrient cycling and resilience, critical for degraded subtropical soils. (3) Productivity gains: The \u003cem\u003eC. oleifera\u0026ndash;P. tricuspidata\u003c/em\u003e system achieved the highest fruit yield (134% increase) and oil production (157 kg ha⁻\u0026sup1;), linking soil conservation directly to economic returns. These findings highlight intercropping as a sustainable strategy for \u003cem\u003eC. oleifera\u003c/em\u003e plantations in erosion-vulnerable regions.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eCRediT authorship contribution statement\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eZeyao Zhao: Writing – review \u0026amp; editing, Supervision, Methodology, Formal analysis, Data curation, Conceptualization. Lin Chen: Methodology, Investigation, Formal analysis. Wanwan He: Investigation, Data curation. Wenjun Xie: Investigation, Formal analysis. Byron B. Lamont: Writing – review \u0026amp; editing, Methodology, Conceptualization. Long sheng Chen: Investigation, Formal analysis, Methodology, Data curation. Li Mei: Writing – review \u0026amp; editing, Validation, Supervision, Resources, Project administration, Methodology, Funding acquisition, Formal analysis, Conceptualization. Zhaogui Yan: Writing – review \u0026amp; editing, Writing – original draft, Visualization, Validation, Supervision, Resources.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eDeclaration of competing interests\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eIn submitting this manuscript, we provide the following statements: (1) No conflict of interest exists in the submission of this manuscript; (2) The manuscript is approved by all authors; (3) The work described was original and has not been published previously, and is not under consideration for publication elsewhere; (4) All the authors listed have made substantial contributions to the research design, or the acquisition, analysis or interpretation of data, or drafting the paper or revising it critically; and (5) Nobody who qualifies for authorship has been excluded.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgements\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis study was supported by National Key Research and Development Program of China (2017YFC0505503). We thank the members of the Hubei Engineering Technology Research Center for Forestry Information Laboratory for their invaluable assistance.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eData availability\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eData will be made available on request.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eAdimassu Z, Tamene L, Degefie DT (2020) The influence of grazing and cultivation on runoff, soil erosion, and soil nutrient export in the central highlands of Ethiopia. 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Sci Hort 292. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/j.scienta.2021.110632\u003c/span\u003e\u003cspan address=\"10.1016/j.scienta.2021.110632\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":true,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"plant-and-soil","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"plso","sideBox":"Learn more about [Plant and Soil](https://www.springer.com/journal/11104)","snPcode":"11104","submissionUrl":"https://submission.nature.com/new-submission/11104/3","title":"Plant and Soil","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"Camellia oleifera, Intercropping treatments, Soil physical and chemical properties, Soil erosion and nutrients loss, Soil microbial community","lastPublishedDoi":"10.21203/rs.3.rs-7271330/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7271330/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003e\u003cstrong\u003eBackground and aims\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cem\u003eCamellia oleifera, a tree species of significant ecological interest and economic value, is widely cultivated in China for its oil production. However, many C. oleifera plantations, particularly in the red soil regions of the Yangtze River Basin and southern China, show low productivity due to soil quality limitations. We hypothesized that intercropping would reduce soil erosion, improve soil conditions, and increase C. oleifera productivity.\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003e\u003cem\u003e\u003cstrong\u003eMethods\u003c/strong\u003e\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003e\u003cem\u003eTo test this hypothesis, we intercropped C. oleifera with three herb species, Parthenocissus tricuspidata, Coreopsis lanceolata, and Mentha haplocalyx, in subtropical Hunan.\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003e\u003cem\u003e\u003cstrong\u003eResults\u003c/strong\u003e\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003e\u003cem\u003eCompared with monoculture, intercropping reduced runoff by 33.9–51.4%, soil loss by 72.4–84.3%, total nitrogen loss by 34.4–56.9%, and \u003c/em\u003etotal phosphorus \u003cem\u003eloss by 48.0–60.1%. \u003c/em\u003eIntercropping also modified soil microbial community composition, enhancing alpha diversity and promoting beneficial taxa such as Acidobacteria (31\u003cem\u003e–\u003c/em\u003e116%) and Verrucomicrobia (15\u003cem\u003e–\u003c/em\u003e820%). \u003cem\u003eFurthermore, intercropping increased soil organic carbon by 7.4–53.8%, soil phosphorus by 2.3–56.4%, and soil urease activity by 40.4–86.0%. Most importantly, intercropping increased C. oleiferaproductivity, with the C. oleifera - Parthenocissus tricuspidata treatment yielding the highest total fruit production (134% greater than the control) and the highest total oil yield (157 kg ha⁻¹).\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003e\u003cem\u003e\u003cstrong\u003eConclusions\u003c/strong\u003e\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003e\u003cem\u003eThese findings support our hypothesis and demonstrate that intercropping is a sustainable land management practice for mitigating soil erosion, enhancing soil health, and boosting productivity in agroforestry systems.\u003c/em\u003e\u003c/p\u003e","manuscriptTitle":"Intercropping reduces soil erosion, improves soil conditions, and increases productivity of a Camellia oleifera plantation","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-08-22 12:15:33","doi":"10.21203/rs.3.rs-7271330/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Major revisions","date":"2025-09-24T07:09:11+00:00","index":"","fulltext":""},{"type":"reviewerAgreed","content":"","date":"2025-08-25T02:33:23+00:00","index":0,"fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-08-15T01:51:22+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"Plant and Soil","date":"2025-08-03T09:24:59+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-08-03T09:13:46+00:00","index":"","fulltext":""},{"type":"submitted","content":"Plant and Soil","date":"2025-08-01T08:38:14+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"plant-and-soil","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"plso","sideBox":"Learn more about [Plant and Soil](https://www.springer.com/journal/11104)","snPcode":"11104","submissionUrl":"https://submission.nature.com/new-submission/11104/3","title":"Plant and Soil","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"fc44250e-6dcc-4ff9-80b1-cd95c887352e","owner":[],"postedDate":"August 22nd, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2025-12-29T16:00:06+00:00","versionOfRecord":{"articleIdentity":"rs-7271330","link":"https://doi.org/10.1007/s11104-025-08199-4","journal":{"identity":"plant-and-soil","isVorOnly":false,"title":"Plant and Soil"},"publishedOn":"2025-12-22 15:57:23","publishedOnDateReadable":"December 22nd, 2025"},"versionCreatedAt":"2025-08-22 12:15:33","video":"","vorDoi":"10.1007/s11104-025-08199-4","vorDoiUrl":"https://doi.org/10.1007/s11104-025-08199-4","workflowStages":[]},"version":"v1","identity":"rs-7271330","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7271330","identity":"rs-7271330","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}