Ecological clusters based on responses of soil microbial phylotypes to precipitation explain ecosystem functions

Ecological classification has been proposed as a way to more tightly link microbial communities and ecosystem functions, but few studies have attempted to relate ecological classifications of microbial communities with specific ecosystem functions. Here, we conducted a 3-year experiment with nine levels of artificial precipitation (100-500 mm) in a typical semi-arid steppe. The first five levels (<300 nun) were considered a "dry" gradient, and the last five (>300 mm) were considered a "wet" gradient. Increases in precipitation under dry and wet gradients did not alter the alpha diversities of soil bacterial, soil fungal, or plant communities, except that increases in precipitation under the dry gradient decreased bacterial alpha diversity. Increases in precipitation under the dry and wet gradients altered the composition of the soil bacterial community but did not alter the composition of the fungal or plant communities. Ecological clusters (ECs) based on the relationships between the relative abundance of phylotypes and dry and wet gradients were correlated with soil C or N mineralization rates; these ECs explained 14-28% of the total variance in soil C and N mineralization rates. In contrast, soil C or N mineralization rates were not correlated with the commonly measured properties (e.g., biomass and diversity) of plant, soil bacterial, and soil fungal communities. Our findings indicate that the grouping of soil microorganisms into ECs based on responses to precipitation gradients can provide insights into the relationships between soil organisms and ecosystem functions.