Losses in microbial functional diversity reduce the rate of key soil processes

The consequences of microbial functional diversity loss on key ecosystem processes remain debatable due to lack of firm evidence from observational or manipulative experiments for a link between microbial functional diversity and specialized ecosystem functions. Here, we conducted a microcosm experiment to test for a link between multiple microbial functional diversity (nitrifiers, methanotrophs and denitriflers) and corresponding specialized soil functions (nitrate availability, methane, and nitrous oxide flux) using the dilution-to-extinction approach. We found that reductions in functional microbial diversity led to declines in the rates of specialized soil processes. Additionally, partial correlations provided statistical evidence that the correlations between microbial functional diversity and specialized functions were maintained after accounting for functional gene abundance (qPCR data) and substrate availability. Our analyses further suggested little redundancy in the relationship between microbial functional diversity and specialized ecosystem functions. Our work provides experimental evidence that microbial functional diversity is critical and directly linked to maintaining the rates of specialized soil processes in terrestrial ecosystems.