competition for N in Forest Soils: Stabilization of Organic N in Recalcitrant Pools

• Applicant: Professorin Dr. Ingrid Kögel-Knabner
• Subject Area: Ecology and Biodiversity of Plants and Ecosystems
• Term: from 2006 to 2010
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 27071968

Our knowledge of the competition for N in forest soils is confounded by incomplete understanding of the partitioning between plants, mycorrhizal fungi, soil microbes and sequestration of N into SOM. A combined approach of field and laboratory investigations together with 15N labelling experiments is proposed to elucidate the major competitive long-term stabilization mechanisms of organic N and the formation and structure of DON. 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 tannin-protein complexes, organo-mineral associations and abiotic N immobilization. Solid-state 15N and 13C NMR spectroscopy will provide information on the binding forms of organic N, MALDI-TOF-MS on tannins in tannin-protein complexes. Chemolytic techniques will allow to quantify hydrolysable proteins in bulks soils and organo-mineral complexes. In the framework of the research group this approach will allow to differentiate and to quantify the stabilization of organic N versus the organic N present in labile forms. In the end this will provide information on the competition for N between plants and microorganisms taking into account the formation and slow turnover of recalcitrant organic N pools in soil.

• DFG Programme: Research Units
• Subproject of: FOR 788: Competitive Mechanisms of Water and Nitrogen Partitioning in Beech-Dominated Decidiuous Forests
• Participating Person: Professorin Dr. Heike Knicker