Effects of farmland mulching patterns on soil microbial diversity and community structure in dryland

土壤微生物是表征土壤质量的敏感指标，采用Illumina HiSep技术分析不同覆盖方式对半湿润易旱区农田土壤微生物群落结构及多样性的影响，以期从微生物的角度评价农田不同覆盖措施对土壤质量的影响。设3种覆盖模式：平作塑料薄膜覆盖（P）、平作秸秆覆盖（S）和垄膜沟播覆盖（R），以平作不覆盖为对照（CK），研究不同覆盖模式下土壤微生物群落变化，分析各土壤理化因子与微生物群落之间的关系。研究结果表明各覆盖处理显著改变了土壤微生物的群落结构和多样性。所有土壤样品中，细菌群落的优势菌门是变形菌门（Proteobacteria）、酸杆菌门（Acidobacteria）、放线菌门（Actinobacteria），丰度分别为29.69%、28.28%和20.76%，CK处理下较高的土壤pH和低NO₃-N含量抑制了土壤中酸杆菌门（Acidobacteria）的生长繁殖，而放线菌门（Actinobacteria）相对丰度为所有处理中最高。真菌群落的优势菌门是子囊菌门（Ascomycota）、担子菌门（Basidiomycota），丰度分别为59.65%和20.96%，S处理下过低的土壤温度抑制了担子菌门（Basidiomycota）生长和繁殖，其相对丰度为所有处理中最低。与CK相比，P和R处理显著提高土壤细菌的多样性和丰富度；S和R处理下土壤真菌多样性和丰富度显著增加，而P处理的土壤真菌多样性和丰富度均无显著差异。斯皮尔曼相关分析表明土壤细菌多样性主要受土壤含水量（SM）和硝态氮含量（NO₃-N）影响，而土壤真菌多样性主要受土壤温度（ST）、全氮（TN）和硝态氮含量（NO₃-N）影响；RDA分析表明微生物群落结构的变化主要受SM、ST、NO₃-N和TN含量的影响。总的来说，R处理下土壤细菌和真菌的多样性和丰富度较CK处理显著提高，该处理下土壤中担子菌门（Basidiomycota）和球囊菌（Glomeromycota）相对丰度为所有处理中最高，两者分别形成的外生菌根和从生菌根不但促进了根部养分的吸收，而且提高了作物的抗逆性，且结果证明该处理的作物产量为最高，因此在半湿润旱作区推荐采用垄膜沟播覆盖种植方式。;Soil microbes are sensitive indicators for characterizing the quality of soil. In this study, Illumina HiSeq was used to analyze the effects of different mulching patterns on the microbial community structure and diversity of semi-humid dryland farmland soil in order to evaluate the impacts of these mulching measures on the soil quality from a microbial perspective. The soil microbial communities were tested under three different mulching patterns comprising film mulching (P), straw mulching (S), and ridge and furrow mulching (R), with conventional tillage without mulching as the control (CK). The relationships between the soil physical and chemical characteristics and microbial communities were analyzed. The results of the study indicated that each mulching treatment significantly changed the soil microbial community structure and diversity. The dominant phyla of bacterial in the soil samples among all treatments were Proteobacteria, Acidobacteria, and Actinobacteria with abundances of 29.69%, 28.28%, and 20.76%, respectively. Actinobacteria had the highest relative abundance under CK, but a high soil pH and low NO₃-N content inhibited the growth and reproduction of Acidobacteria in the soil. The dominant phyla of fungi were Ascomycota and Basidiomycota with abundances of 59.65% and 20.96%, respectively. The low soil temperature under the S inhibited the growth and development of Basidiomycota, and its relative abundance was the lowest among all treatments. Compared with CK, P and R significantly increased the diversity and richness of soil bacteria, while S and R significantly increased the soil fungi diversity and richness, and P had no significant effects on the soil fungi diversity and richness. Spearman's rank correlation coefficients showed that the soil bacterial diversity was mainly affected by the soil moisture(SM) and nitrate nitrogen contents(TN), and the soil fungi diversity was mainly affected by the soil temperature(ST), total nitrogen, and nitrate nitrogen(NO₃-N). Redundancy analysis showed that the microbial community structure was affected mainly by the soil moisture, soil temperature, nitrate nitrogen, and total nitrogen. In general, the diversities and abundances of soil bacteria and fungi were significantly higher under R than CK. The relative abundances of Basidiomycota and Glomeromycota were the highest under R in all treatments. The ectomycorrhiza and secondary mycorrhiza formed by these phyla can enhance the absorption of root nutrients as well as improve the stress resistance by crops. The results showed that the crop yields were the highest under R. Ridge and furrow mulching is recommended as the planting method in this semi-humid dry farming area.