The aim is to test the soil biodiversity-function relationship in soils with varying microbial community diversity and structure. The main hypothesis to be tested is whether the diversity within selected functional groups of microorganisms (microbial guilds) determines the function.

Changes in soil microbial diversity will be brought about by the application of physical and chemical stressors. The analysis of soil function is based on the respiration of organic substrates, while the diversity of the functional groups is investigated by stable isotope probing methods and molecular analyses.

The relationship between biodiversity and ecosystem function has been extensively investigated. However, no consensus has been reached as to whether community diversity plays a role in ecosystem functioning. Using natural soil microbial communities with their highly diverse flora, the effects of a reduction in the initial diversity can be studied. However, such research has so far been hampered by a lack of simple experimental methods linking microbial community structure and function. In this project, we apply stable isotope probing (SIP) in combination with DNA techniques. This enables systematic investigations of the relationship between microbial diversity and function. Soil microcosms will be exposed to multiple physical and chemical stressors, in order to test community resistance and resilience. The SIP investigations will be compared with classical measures of soil function (such as respiration) as well as microbial diversity (T-RFLP) measurements. The experiments will be accomplished with modeling of the community structure - process relationship. With this approach, we will assess to what extent the total diversity of the microbial community or the diversity within a selected functional group determine the severity of adverse effects of stressors.

The baseline of carbon transformation in Dutch soils