水保措施对柑橘果园土壤细菌群落结构的影响

为探索水保措施对柑橘果园土壤细菌群落结构的影响，以江西省德安县柑橘果园为研究对象，选取4种水保措施狗牙根条带覆盖（TD）、狗牙根全园覆盖（QY）、经济作物萝卜-大豆轮作条带覆盖（LZ）和净耕果园（JG）]，基于高通量测序技术确定了柑橘果园土壤不同土层表层（0~10 cm）、中层（10~20 cm）、底层（20~40 cm）]的细菌群落结构，并采用PLS-DA分析和冗余分析（RDA）等统计方法研究了不同水保措施条件下柑橘果园细菌群落结构特征及差异.结果表明:①与JG相比，TD、QY和LZ各层土壤中的全氮（TN）、土壤有机碳（SOC）和土壤有机质（SOM）含量均有提高，尤其是QY提高明显，其3层土壤中的平均TN、SOC和SOM含量分别提高了近50%、40.33%和40.26%.②与JG相比，QY表层土壤的细菌丰度显著增加了近1.51倍，且不同水保措施下QY表层和TD中底层土壤的Shannon-Wiener指数分别最高.③柑橘果园土壤中主要细菌门有Chloroflexi（28.39%~45.32%）、Acidobacteria（13.20%~23.31%）、Proteobacteria（14.65%~22.95%）和Actinobacteria（7.20%~11.26%）.与TD、QY和LZ相比，JG土壤中Chloroflexi的相对丰度较高，Acidobacteria和Proteobacteria的相对丰度较低.除Chloroflexi相对丰度增加外，不同水保措施下Proteobacteria和Actinobacteria的相对丰度均沿剖面深度呈减少趋势；不同水保措施下Acidobacteria的相对丰度亦沿剖面深度呈减少趋势，但TD除外.④不同水保措施下土壤细菌群落差异显著，TN、SOC和SOM（尤其是TN）是主要影响因素.⑤网络分析表明，Proteobacteria是4种水保措施下土壤细菌交互作用的核心细菌；QY土壤细菌群落交互作用网络的稳定性优于TD、LZ和JG.研究显示，水保措施可以通过改变土壤理化环境来影响细菌群落结构，TD、QY和LZ均提高了土壤中的TN、SOC和SOM含量，增加了土壤细菌多样性，其中以QY的提高最为显著，且土壤细菌群落交互作用的稳定性最好. 

Effects of Soil and Water Conservation Measures on Soil Bacterial Community Structure in Citrus Orchards

In this study, the effects of soil and water conservation measures on the characteristics of soil bacterial communities were studied in a citrus orchard in De''an, Jiangxi Province. We sampled soil at three depths (surface soil 0-10 cm, middle soil 10-20 cm and subsurface soil 20-40 cm) in the citrus orchard under long-term soil and water conservation measures, which were Bermudagrass strip intercropping (TD), Bermudagrass full coverage (QY), radish-soybean crop rotation strip intercropping (LZ) and clear tillage orchards (JG). High-throughput sequencing was used to analyze the soil bacterial communities. Partial least squares discriminant analysis (PLS-DA) and redundancy analysis (RDA) were used to investigate the structural characteristics and differences of bacterial communities in the citrus orchards. The results showed that:(1) Compared to JG treatment, the contents of total nitrogen (TN), soil organic carbon (SOC) and soil organic matter (SOM) contents in all soil layers under the TD, QY and LZ treatment (especially QY treatment) were significantly higher. The average TN, SOC and SOM contents in the surface, middle and subsurface soils under the QY treatment were approximately 50%, 40.33% and 40.26% higher than those in the TD, LZ and JG treatments, respectively. (2) The bacterial abundance in the surface soil under QY treatment was 1.51 times higher than JG treatment. The Shannon-Wiener index of the surface soil bacteria under QY treatment was the highest, and of the middle and subsurface soil bacteria under TD treatment was the highest. (3) Chloroflexi (28.39%-45.32%), Acidobacteria (13.20%-23.31%), Proteobacteria (14.65%-22.95%) and Actinobacteria (7.20%-11.26%) were the dominant bacterial phyla in the citrus orchard soil. Compared with other treatments, the relative abundance of Chloroflexi was higher, and the relative abundance of Acidobacteria and Proteobacteria was lower in JG treatment. The relative abundance of Chloroflexi increased along the soil profile under the four treatments, while the relative abundance of Proteobacteria, Acidobacteria and Actinobacteria decreased (except for Acidobacteria under TD treatment). (4) There were significant differences in soil bacterial communities under four soil and water conservation measures, and TN, SOC and SOM were the main factors that determined the characteristics of bacterial communities. (5) The network analysis revealed that Proteobacteria was the core bacteria involved in the soil bacteria interaction under the four soil and water conservation measures. And the stability of soil bacterial community interaction under QY treatment was higher than TD, LZ and JG treatments. The four soil and water conservation measures affected the soil bacterial community structure by changing the physical and chemical environment of soil. This study shows that the TD, QY and LZ treatments have increased the contents of TN, SOC and SOM in the soil, and increased the diversity of soil bacteria. Among them, the QY treatment has the best effects.