Temperature and aridity index as the dominant drivers for large-scale distribution of soil diazotrophic communities across various forests. Diazotrophs in forest soils

We investigated the distribution of soil diazotrophic communities at 146 sites by nifH gene amplicon sequencing, and assessed the relative contributions of environmental variables along a 3900 km south-north transect in China’s forests. Statistical analysis showed that temperature and aridity index were the predominant climatic parameters governing diazotrophic community diversity and structure, mainly through their indirect effects on soil pH, multi-nutrients (e.g., P, Ca, Mg, Fe) and plant coverage. The distinct responses of different diazotrophs to climatic factors and large heterogeneity of diazotrophic diversity among various climatic-zone forests further support this contention. These results indicate the presence of differentiated climatic niches for diazotroph taxa (Bradyrhizobium, Azospirillum and Methyloferula).

本研究沿中国森林带3900公里的南北样带，通过nifH基因扩增子测序技术，对146个样点的土壤固氮微生物群落（diazotrophic communities）的分布特征进行了调查，并评估了各类环境变量的相对贡献度。统计分析结果显示，温度与干旱指数是调控固氮微生物群落多样性与群落结构的主导性气候参数，其调控作用主要通过间接影响土壤pH值、多种营养元素（如磷、钙、镁、铁）及植物覆盖度实现。不同固氮微生物类群对气候因子的差异化响应，以及不同气候带森林间固氮微生物多样性的显著异质性，进一步佐证了上述结论。本研究结果表明，固氮微生物类群（慢生根瘤菌属Bradyrhizobium、固氮螺菌属Azospirillum及甲基费罗拉菌属Methyloferula）具备分化的气候生态位。