Higher-diversity soil bacterial communities are more resistant to the effects of nutrient addition

Large scale soil surveys reveal soil bacterial diversity is strongly correlated with a number of soil edaphic variables including pH and nutrient status. What is less clear is whether soil communities that differ in their diversity are differentially able to resist perturbations. Here we present data on bacterial communities sampled from a large-scale, fully factorial grassland field experiment examining the effects of above-ground biotic manipulations (grazing, insecticides, molluscicides) and below-ground nutrient additions on soils manipulated to two differing pH levels. We measured molecular fingerprints of the bacterial communities using tRFLP, and also assayed metabolic activity associated with each of the plots. We found that nutrient additions significantly affected the pH-4 soil communities but had lesser effects on the higher pH-7 soils, indicating that the lower diversity soils were more susceptible (or less resistant) to perturbations arising from nutrient addition. These results call for further manipulative studies to understand feedbacks between microbial diversity and co-varying soil chemical parameters.