Carbon Flux Through the Soil Animal Food Web

The proposed project examines the trophic transfer of carbon into the soil animal food web of a maize field. Carbon and energy fluxes are monitored by stable isotope and lipid analyses. Whole animal 15N/14N and 13C/12C ratios, fatty acid pattern, and compound specific analysis of 13C/12C in individual fatty acid biomarkers are determined to ascribe species to trophic levels and to identify major food resources. In rhizosphere and detrital based topsoils the availability of resources (recalcitrant/labile) to the fauna, and their role in sequestration and transfer, is estimated using fatty acids as major carbon currency. A gradient from this resource rich to deeper oligotrophe habitats with low diverse food webs is investigated for the nematode fauna. Two joint laboratory experiments will be performed to evaluate (i) short-term carbon fluxes into the decomposer system, and (ii) trophic interactions in the fungal energy channel in detail. As basis for the carbon flux model functional response experiments with dominant mesofauna species will be performed. Coupling qualitative and quantitative data on decomposer populations with isotope-ratio mass-spectrometry of biomarker fatty acids in microorganisms and animals will allow to connect microbial and faunal food web, and to directly link faunal functional groups, or even individual species, with specific processes in the soil C cycle.