中华鳖投放密度对稻鳖共生田土壤细菌群落结构的影响

【目的】明确稻鳖共生模式下稻田土壤微生物多样性及菌群结构组成的变化特征，为推广稻鳖共生模式及开展稻田土壤微生物功能研究提供理论依据。【方法】水稻移栽25 d后投放中华鳖，于8月10日、9月19日和10月10日采用五点法分别在水稻根部周围和鳖池水底采集0~5 cm表层土，应用Illumina MiSeq高通量测序分析稻田表层土壤和鳖池底泥的菌群结构特征及其多样性，并以冗余分析（RDA）识别稻鳖共生田土壤菌群结构变化的关键环境因子。【结果】放养中华鳖后稻鳖共生田土壤的理化性质均发生明显变化。从24份样品中测序获得145239个OTUs，涵盖的菌群涉及到74门184纲294目301科373属。各样品均具有较高的丰度和多样性，Chao1指数范围为7817.78~17453.39，Shannon指数范围为8.64~11.29，且中华鳖投放密度低的稻鳖共生田土壤菌群多样性相对较高。在稻田表层土壤和鳖池底泥菌群结构中，相对丰度大于1.00%的门共有10个，分别是变形菌门（Proteobacteria）、绿弯菌门（Chloroflexi）、酸杆菌门（Acidobacteria）、拟杆菌门（Bacteroidetes）、硝化螺旋菌门（Nitrospirae）、厚壁菌门（Firmicutes）、Ignavibacteriae、螺旋体门（Spirochaetes）、芽单胞菌门（Gemmatimonadetes）和疣微菌门（Verrucomicrobia），以变形菌门的相对丰度最高，达28.96%~64.76%；丰度大于1.00%的属有16个，相对丰度排名前10的属包括f_Anaerolineaceae、地杆菌属（Geobacter）、厌氧粘细菌属（Anaeromyxobacter）、f_Acidobacteriaceae_Subgroup_1]、寡养单胞菌属（Stenotrophomonas）、Sideroxydans、c_SBR2076、f_Nitrosomonadaceae、c_Bacteroidetes_vadinHA17和f_FW13。RDA分析结果表明，与稻鳖共生田土壤菌群结构分布极显著（P<0.01）相关的环境因子有pH、总氮（TN）含量和有机质（OM）含量，其中pH对稻鳖共生田土壤菌群结构分布影响最大。【结论】稻鳖共生模式能促进稻田土壤中氮、磷、钾的累积，有效提高土壤养分，且中华鳖投放密度低的稻田土壤菌群多样性相对较高。pH、TN含量和OM含量对稻鳖共生田土壤菌群结构的变化产生极显著影响，因此在实际生产中，中华鳖投放密度的确定除了要结合水稻和中华鳖的生产性能外，还应考虑稻鳖共生模式中饲料化肥的环境释放特点、营养物质循环特征及微生物结构组成等。

Effects of Chinese soft-shelled turtle density on soil bacterial community structure in rice-turtle intergrowth field

【Objective】To clarify the variation characteristics of soil microbial diversity and bacterial community structure under rice-turtle symbiotic model, and to provide theoretical basis for the promotion of rice-turtle intergrowth model and the study of soil microbial function in rice field.【Method】Chinese soft-shelled turtles were placed 25 d after the rice was transplanted. On August 10, September 19, and October 10, the five-point method was used to collect 0-5 cm topsoil around the root of rice and the bottom of turtle pond, respectively. Illumina MiSeq high-throughput sequencing was used to analyze the characteristics and diversity of bacteria in soil and the bottom mud of the Chinese soft-shelled turtle pond, and redundancy analysis(RDA) was used to identify the key environmental factors affecting the structural changes of soil bacteria in rice-turtle symbiotic field.【Result】The results showed that the physical and chemical properties of soil in rice-turtle symbiotic field changed greatly after putting Chinese soft-shelled turtle. 145239 OTUs were obtained from 24 samples, covering 74 phyla, 184 classes, 294 orders, 301 families and 373 genera. Each sample had high richness and diversity, with Chao1 index range of 7817.78-17453.39, and Shannon index range of 8.64-11.29. Moreover, the diversity of soil microbial community in rice-turtle symbiotic field with low stocking density was relatively high. There were 10 phyla with relative abundance greater than 1.00% in the soil of rice-turtle symbiotic field and bottom mud of turtle pond. They were Proteobacteria, Chloroflexi, Acidobacteria, Bacteroidetes, Nitrospirae, Firmicutes, Ignavibacteriae, Spirochaetes, Gemmatimonadetes and Verrucomicrobia, respectively. The relative abundance of Proteobacteria was the highest, reaching 28.96%-64.76%;there were 16 genera with abundance greater than 1.00%. The top 10 genera with relative abundance included f_Anaerolineaceae, Geobacter, Anaeromyxobacter, f_Acidobacteriaceae_【Subgroup_1】, Stenotrophomonas, Sideroxydans, c_SBR2076, f_Nitrosomonadaceae, c_Bacteroidetes_vadinHA17 and f_FW13. The results of RDA analysis showed that pH, total nitrogen(TN) content and organic matter(OM) content were extremely correlated to the distribution of soil microbial community structure in the rice turtle symbiotic field(P < 0.01), and pH had the greatest impact on the distribution of soil microbial community structure in the rice-turtle symbiotic field.【Conclusion】The rice-turtle symbiosis model can promote the accumulation of nitrogen, phosphorus, and potassium in the paddy soil, and effectively improve the soil nutrients, and the soil microbial diversity of the paddy field with low stocking density of the Chinese soft-shelled turtle is relatively high. The pH, TN content and OM content have extremely significant indigenous effects on the changes of soil microbial community structure in the rice-turtle symbiotic field. Therefore, in the actual production, the determination of the feeding density of turtle should not only combine the production performance of rice and turtle, but also consider the environmental release of feed and fertilizer, nutrient cycling characteristics and microbial structure in the symbiotic mode of rice and turtle.