The effect of biodiversity on nutrient cycling in an experimental grassland

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Species and/or functional diversity of experimental grassland communities may influence the soil nutrient cycle. The objectives of our proposal are (1) to quantify nutrient retention (N, P, K, Ca, Mg, S, Cu, Mn, Zn) by setting up an ecosystem budget including all inputs and outputs, (2) to determine the contribution of organic N, P, and S in soil solution to nutrient cycling, and (3) to assess soil N processes with the help of the N isotope composition in inorganic N species in differently diverse experimental grassland communities. We will collect soil solid phase samples, precipitation above and below the grass canopy, and soil solution with porous suction plates at 10, 20, 30, and 60 cm soil depth in one of the four blocks of the Jena biodiversity experiment and at 30 am depth in two other blocks (66 plots). Dry deposition will be estimated with a chloride tracer method. Nutrient leaching will be assessed with available models in close cooperation with the hydrological subproject. We expect answers to the questions whether increasing species diversity per se or increasing functional diversity result in increasing nutrient use and whether more diverse grassland systems are more stable than less diverse systems as indicated by the balance between nutrient inputs and outputs.