Biogeographic Patterns of Soil Microbial Biomass in Alpine Ecosystems Depend on Local Rather Than Regional Drivers

Aim

Conflicting distribution patterns of soil microbes along the elevation gradient in alpine ecosystems have been suggested based on observations from individual mountains. There remains a lack of biogeographical studies spanning multiple latitudes and climate zones, a scale appropriate to reveal general ecological patterns of soil microbial biomass (SMB) for alpine ecosystems. We conducted a large-scale sampling campaign along elevational gradients in seven mountains across mainland China and investigated the biogeographical patterns of soil microorganisms and quantified the influencing environmental factors.

Location

China.

Time Period

2019.

Major Taxa Studied

Seed plant species and soil microorganisms.

Methods

We sampled aboveground plants and belowground soils along elevational gradients from closed forests located below the alpine treeline up to the upper elevational limit of vegetation in seven mountains. We analysed the distribution patterns of SMB and the ratio of fungi to bacteria (F/B) and quantified four types of environmental factors at local (i.e., plant functional traits, soil physicochemical properties, and topography) and regional (i.e., macroclimate) scales to determine the drivers of microbial biomass in alpine ecosystems.

Results

We observed a hump-shaped pattern of SMB along the elevation gradients, with a maximum near the alpine treeline. The soil nutrient status and plant functional traits played the most decisive roles in shaping SMB. Local-scale environmental factors were more important than regional factors in determining SMB in alpine ecosystems.

Main Conclusions

Our study suggests that distribution patterns of SMB in alpine ecosystems are closely related to environmental heterogeneity rather than elevation alone. In the context of future temperature rises with global change, soil microbes can more easily track localised changes in microhabitats compared with top-down effects of macroclimate, indicating that effects of climate warming on soil microbes could possibly be buffered by local environmental factors in alpine ecosystems.