Assembly changes of soil microorganisms during the transformation from native soil to alfalfa cultivation soil in Kunlun mountain sand area, Xinjiang

It is considered to be an effective means to improve desertified and degraded soil by biology, but it is still unclear how the effect is in high altitude desertified soil environment and how the microorganisms of soil and plants are assembled when the host plants of native soil are changed. We observed and analyzed whether the change from native soil to alfalfa soil affected the community aggregation of soil microorganisms and whether this led to the diversity of microorganisms. The results showed that alfalfa cultivation improved the quality of native soil, and with the extension of planting time, it promoted the recovery and homogenization of soil microbial diversity. This process is accompanied by the replenishment or expulsion of soil microorganisms, and soil organic matter and pH are the driving factors of microbial community change. Only 541/56 clusters of bacteria/fungi OTUs were always present in native soil, cultivated soil and rhizosphere soil, but this core microbial group accounted for a large part of all readings (bacteria: 28.70%, fungi: 40.37%). The complexity of microbial network structure and interaction between native soil and rhizosphere soil is higher than that of cultivated soil, and the performance of bacteria is more obvious than that of fungi. On the whole, the transition from native soil to cultivated soil by planting alfalfa has a positive impact on the local microbial diversity, and the assembly of microorganisms is affected by the recruitment and dispersion of alfalfa rhizosphere soil.

生物修复手段被视作改良荒漠化退化土壤的有效途径，但目前仍有两个关键科学问题尚未明确：一是该手段在高海拔荒漠化土壤环境中的实际改良效果；二是当本土土壤的宿主植物发生改变时，土壤与植物共生微生物的组装机制如何。本研究通过观测与分析，探究了将本土土壤改造为苜蓿种植土壤后，是否会影响土壤微生物的群落聚集过程，以及该过程是否会改变土壤微生物多样性。研究结果显示，苜蓿种植可有效改善本土土壤质量；随着种植时长的增加，还可促进土壤微生物多样性的恢复与均质化。该微生物群落重塑过程伴随土壤微生物的补充或移除，而土壤有机质与pH值是驱动微生物群落结构改变的核心因子。仅541个细菌操作分类单元（Operational Taxonomic Units, OTU）与56个真菌OTU同时存在于本土土壤、耕作土壤与根际土壤中，但该核心微生物类群在所有测序读数中占比极高（细菌：28.70%，真菌：40.37%）。本土土壤与根际土壤的微生物网络结构复杂度及物种间互作强度均高于耕作土壤，且该差异在细菌群落中的表现较真菌群落更为显著。总体而言，通过种植苜蓿将本土土壤改造为耕作土壤，对当地微生物多样性具有积极影响；而微生物的组装过程则受到苜蓿根际土壤的微生物招募与扩散过程的调控。