生物固氮在农田生态系统中占有重要地位，作物总生物量中有大约24%的氮来源于微生物的非共生固氮过程。根际作为微生物活跃的关键地带，固氮微生物群落的竞争与协同作用共同促进了根际环境的稳定及养分循环过程。近年来，对于固氮功能微生物的研究主要关注固氮菌群落组成及其分布特征，而对于固氮菌种间相互关系、群落构建过程及其驱动因子的研究较少。
基于此，褚海燕课题组在大的空间尺度下研究了华北平原小麦根际固氮菌的群落组成和多样性，重点探讨了根际固氮菌种间网络关系、群落构建过程及其驱动机制。结果表明，根际固氮菌群落显著区别于非根际土壤，且根际中固氮菌网络结构相对简单却更加稳定；总体水平上，确定性过程主导了麦田土壤固氮菌的群落构建，而在根际中，随机性过程的贡献率升高；在中性pH（6.5-7.5）梯度下，固氮菌群落构建由随机性过程占主导，而在酸性pH（4.5-6.5）或碱性pH（7.5-8.5）梯度下，固氮菌群落构建由确定性过程占主导。本研究阐释了根际环境中相对稳定的固氮菌群落，并解析固氮菌群落构建过程及其影响因素，为进一步挖掘和重建稳定的农田根际固氮微生物群落提供了科学依据。
Fan KK, Pamela Weisenhorn, Jack A. Gilbert, Shi Y, Bai Y, Chu HY. Soil pH correlates with the co-occurrence and assemblage process of diazotrophic communities in rhizosphere and bulk soils of wheat fields. Soil Biology and Biochemistry, 2018, 121: 185-192
Abstract
Biological nitrogen fixation contributes to the pool of plant-available N in both bulk soil and the rhizosphere. Here we investigated the co-association and assemblage process of diazotrophic community members in both rhizosphere and bulk soil of wheat fields. The diazotrophic community structure in the rhizosphere was significantly different and comprised a less competitive and more stable network structure when compared with that of the bulk soil. Deterministic versus stochastic community assemblage processes were quantified using betaNTI scores, demonstrating that deterministic processes decreased in importance with distance from plant roots. Soil pH was correlated with diazotrophic community structure and diversity, and community structure showed greater connectivity and stability in soils with neutral pH relative to those in acidic or alkaline soils. Stochastic processes dominated the assemblage of the diazotrophic community in soils with neutral pH, while deterministic processes dominated in acidic or alkaline soils. These results suggest that soil pH may play an essential role in the interaction and assemblage processes of the diazotrophic community in the rhizosphere and bulk soils, which could enhance our understanding of biological nitrogen fixation in agricultural soils.
