Assessing soil ecosystem processes - biodiversity relationships in a nature reserve in Central Europe

Plant diversity - ecosystem processes relationships are essential to our understanding of ecosystem functioning. We aimed at disentangling the nature of such relationships in a mesotrophic grassland that was highly heterogeneous with regards to nutrient availability. Rather than targeting primary productivity, like most existing reports do, we focused our study on belowground ecosystem processes. We tested three, largely mutually exclusive, hypotheses of ecosystem processes relationships: the redundancy hypothesis, the insurance hypothesis and the centrifugal model hypothesis. We sampled the grassland twice within a single plant growing season in a spatially explicit way and assayed the soil for nitrification, urease activity, relative bacterial activity and a microbial community profile based on respiration while we simultaneously assessed plant diversity. Results supported the centrifugal model. We justify the lack of support for the other two hypotheses on the basis of having conducted an observational study in an environmentally heterogeneous site. The centrifugal model hypothesis appears to be a very good predictive model for explaining diversity in observational, heterogeneous studies. The specific study represents one of the few observational studies that consider measures of ecosystem functioning other than primary productivity.