*Article* **The Changes in Soil Microbial Communities across a Subalpine Forest Successional Series**

**Zhihui Wang 1, Yi Bai 1, Jianfeng Hou 1, Fei Li 1, Xuqing Li 1, Rui Cao 1,2, Yuyue Deng 1,3, Huaibin Wang 1,4, Yurui Jiang 1,5 and Wanqin Yang 1,\***


**Abstract:** Knowledge regarding changes in soil microbial communities with forest succession is vital to understand soil microbial community shifts under global change scenarios. The composition and diversity of soil microbial communities across a subalpine forest successional series were therefore investigated in the Wanglang National Nature Reserve on the eastern Qinghai-Tibet Plateau, China. The calculated diversity indices of soil bacteria (8.598 to 9.791 for Shannon-Wiener, 0.997 to 0.974 for Simpson, 4131 to 4974 for abundance-based coverage estimator (ACE) and 3007 to 3511 for Species richness indices), and ACE (1323 to 921) and Species richness (1251 to 879) indices of soil fungi decreased from initial to terminal succession stages, but Shannon-Wiener and Simpson of soil fungi indices varied slightly with forest succession. Meanwhile, the composition and structure of soil microbial communities varied markedly with forest succession. The relative abundance of the dominant bacterial phyla (*Acidobacteria*, *Firmicutes* and *Actinobacteria*) and fungal taxa (*Mortierellomycota*, *Rozellomycota* and unassigned phylum clade GS01) varied considerably with forest succession. However, regardless of successional stage, *Proteobacteria* and *Acidobacteria* dominated soil bacterial communities and *Ascomycota* and *Basidiomycota* dominated soil fungal communities. Moreover, the changes in soil microbial diversity with forest succession were significantly affected by soil pH, soil organic carbon, soil temperature, altitude, and non-woody debris stock. Importantly, soil pH was the dominant driver of soil microbial community shift with forest succession. In conclusion, the forests at different succession stages not only conserve same microbial populations, but also nurse unique microbial diversity across the forest succession series; and the biodiversity of soil bacterial and fungal communities has differential responses to forest succession.

**Keywords:** bacterial community; forest succession; forest variables; fungal community; non-woody debris; soil biodiversity
