Competition for N in forest soils: stabilization of organic N in recalcitrant pools

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The overall objective of this project is to elucidate the major competitive stabilization and destabilization processes of soil organic nitrogen (SON). Our results from the previous research show that the association in organo-mineral compounds is the major process for N stabilization in Rendzina soils investigated by the research group. This will be achieved by participating in the joined short- and long-term mini-lysimeter experiments at the NE and SW slope of Tuttlingen as well as the ongoing 15N litter labelling experiment. Quantitative data will be generated on the N transferred to non-microbial, recalcitrant organic matter pools and thus, the relevance of major long-term stabilization processes via formation of organomineral associations. At the same time, the experiments provide information on responses of climate change conditions on in situ SON stabilization processes. The physical soil fractionation scheme will provide a quantitative evaluation of the amount of N stabilized in organo-mineral associations. Overall, we will provide information on the competition for N between plants, microorganisms and soil by taking into account the formation and slow turnover of recalcitrant organic N pools, especially the organo-mineral N in soil.