Effects of land use, dispersal and dead wood on the trophic ecology, community structure and reproductive mode of oribatid mites (Oribatida, Acari)

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The factors and processes that affect animal communities are little understood. Theoretically, animal communities are either predictable and structured mainly by niche processes or randomly assembled and structured by stochastic processes (neutral theories). For aboveground arthropod communities, microorganisms and for tropical plant communities these processes are well investigated. In contrast, the structuring forces of animal communities living in soil are little studied and poorly understood. The DFG project Biodiversity Exploratories provides an excellent framework for advancing the understanding of the factors responsible for assembling soil animal communities. A perfect model group for studying the structuring forces for soil animal communities are oribatid mites. They are very abundant and diverse soil animals. Land-use is one of the main factors affecting terrestrial ecosystems. Humans started to modify terrestrial ecosystems since about 10,000 years; however, the greatest changes occurred in the last 150 years due to intensified agriculture and mechanized logging of forest. Overall, more than half of the earth surface is altered by human activities. Since land-use will remain a main driver of animal communities in temperate forests and since land use is likely to interact with global warming it is of eminent importance to better understand soil animal communities and the factors affecting their assemblage. This is the main aim of the proposed project. More specifically, we investigate (1) long-term decomposition of dead wood along a forest land-use gradient. Our hypothesis is: Oribatid mite communities on the bark of dead wood are affected by forest land-use intensity but also by the local communities of the Schorfheide, Schwäbische Alb and Hainich (environmental filtering vs. niche hypothesis). The communities will change over time with environmental filtering getting more important. Second (2) we ask: Which factors structure oribatid mite assemblages in soil and litter by using the method of Community Phylogenetics. We posit that oribatid mite communities are mainly structured by abiotic factors and by trophic niches that are available (niche hypothesis). Third (3) we investigate the long-term temporal dynamics of oribatid mites of the 25 forest core study sites of the Biodiversity Exploratories along a land-use gradient. We hypothesize that Land-use intensity little affects oribatid mite community dynamics in the long term since oribatid mite communities are rather indifferent with regard to forest type/land-use intensity, and are known to be rather constant and predictable over long time periods. Finally (4) we investigate the resilience of oribatid mite communities as affected by forest land-use intensity. We hypothesize that the recovery of oribatid mite communities is faster in natural forest systems such as natural beech forests as compared with heavily managed forest ecosystems such as coniferous forests.