Plant diversity enhances soil microbial biomass and functions irrespective of warming scenarios
Anthropogenic changes in biodiversity and atmospheric temperature rise significantly influence ecosystem processes. However, little is known about the interactive effects of biodiversity and warming on soil microbial biomass and functions in grassland. Here, we report results from the BAC experiment (Biodiversity And Climate) in Cedar Creek, MN, USA, where we studied effects of varying plant diversity (1, 4, and 16 species) and temperature rise (ambient, +1.5°C, and +3°C) on soil microbial biomass, respiration, nutrient limitations, and activities of extracellular enzymes in 2011 and 2012. The focal enzymes are involved in essential biogeochemical processes of the carbon cycle (cellobiohydrolase, ß-1,4-glucosidase, ß-1,4-N-acetylglucosaminidase, Phenol oxidase and Peroxidase), nitrogen cycle (urease), and phosphorus cycle (acid phosphatase).
We found fairly consistent results in both years. Soil microbial biomass as well as most enzyme activities increased significantly with increasing plant diversity. However, we found no significant warming effects on soil microbial properties suggesting temperature optima for soil organisms are sufficiently broad to buffer them against small changes in temperature. In contrast to our expectations, we also found no interactive effects of plant diversity and warming indicating that plant diversity significantly influences soil microbial properties irrespective of warming scenarios. Overall, we found plant diversity to strongly affect soil microorganisms across years and temperature treatments whereas temperature had non-significant effects on soil microorganisms and microbial functions, pointing to the significance of plant diversity in driving belowground processes.