FOR 918: Carbon Flow on Belowground Food Webs Assessed by Isotope Tracers

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The overall goal of the Research Unit is to understand the flow of carbon through biotic compartments within terrestrial ecosystems. Field experiments will be performed at an agricultural site located at Darmstadt with permanent C3 crop. The 13C signal will be introduced by cultivating the C4 plant Zea mays either as corn or fodder maize. Corn maize will introduce above- and belowground plant carbon (i.e. labile and recalcitrant resources), whereas with fodder maize carbon predominantly derives from rhizodeposits (i.e. labile resources). Carbon assimilation and partitioning in the major energy pathways based on roots, bacteria or fungi will be assessed, taking into consideration the factors as resource quality and availability as well as food web complexity. The Research Unit will apply isotope tracer methods for identification of key biota and quantification of the carbon flux in the trophic cascade. This includes the incorporation of 13C label into biomarkers such as lipids and nucleic acids. In addition, attention will be given to the overall carbon balance, i.e. turnover and losses in the soil system. Experimentally assessed biomass-fluxes (respiration and assimilation rates) and allometric functional responses (predator-prey interactions) within food web biota will complete the picture. The present study is unique in its aim to