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

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).