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Beschreibung:
The influence of soil fauna on turnover processes and nutrient cycling in terrestrial habitats is fairly well studied. By contrast, the impact of the burrowing, feeding and excreting activity of soil animals on the physical characteristics of soils is far from being understood, even less if we consider anthropogenically shaped environments like urban habitats. Urbanization, though, is a major ongoing land use change worldwide and it is of particular interest to understand the functioning of urban ecosystems and the provision of ecosystem services useful to man in urban areas (e.g. provision of clean drinking water, reduction of flood risk, mitigation of climate change consequences) all linked to the capacity of urban soils to infiltrate, conduct, filter and store water from the soil surface. Aim of the subproject FAUNA within the research group was to characterize the functional impact of soil animals on turnover processes and on the water distribution dynamics in urban soils. In a series of experiments with mesocosms in field and lab, we studied how the burrowing activity of endogeic earthworms and the mixing of soil particles with excretion products may modify the structure of the soil horizons, the water distribution patterns and the processes of nutrient release in urban soils. The set up of mesocosms equipped with electrodes for the measurements of Electical Resistivity Tomography (ERT) and Time Domain Reflectometry (TDR) probes allowed to trace in situ and noninvasively subsequent desiccation, infiltration and rewetting processes in the soils. The soil animals greatly modified the infiltration and the storage of water in the soils. This occurred interestingly not in reducing the specific actual hydrophobicity of the soils, but by changing the pore size distribution, increasing the saturated water conducitivity and enhancing clearly the water contents in the urban soil horizonts.