Effects of vegetation type, fine and coarse roots on soil microbial communities and enzyme activities in eastern Tibetan plateau

Microbial communities and enzyme activity in soil are the functional link through which the vegetation type occupying a site, may alter soil processes fundamental to nutrient cycling. Roots are known to regulate soil carbon (C) input, but the impacts of different classes of roots on soil microbial community (as indexed by PLFAs) and enzyme activity are uncertain. Thus, the aim of this study was to assess how different classes of woody roots (fine roots ≤ 2 mm and coarse roots > 2 mm) in Pinus tabulaeformis (PT) and Cercidiphyllum japonicum (CJ) plantations influence the microbial community and enzyme potential activity, as compared to natural shrubland. In the fine root rhizosphere soil, the PT and CJ plantations had lower abundances of fungal and gram-positive bacterial PLFAs, and the PT plantation had significantly lower acid phosphatase, dehydrogenase, and higher invertase activities compared to the shrubland. The shrubland and CJ plantation had distinctly higher soil microbial parameters (total, fungal, and arbuscular mycorrhizal fungal PLFAs) and enzyme activities (urease, acid phosphatase, invertase, β-glucosidase, and dehydrogenase) in the fine root rhizosphere than in the coarse root rhizosphere and bulk soils. We concluded that soil organic carbon (SOC) (much more significant) and total nitrogen (TN) were the main factors in regulating soil microbial community and enzymes. Our findings demonstrate the importance of fine roots in regulating microbial community and function. Our results also highlight that differences between fine root rhizosphere and coarse root rhizosphere, or bulk soil are dependent on vegetation type.