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

由于不完全理解植物、菌根真菌、土壤微生物之间的分配以及氮在土壤有机质中的固定，我们对森林土壤中氮的竞争的认识是混乱的。采用野外调查和实验室调查相结合的方法，结合15N标记实验，阐明有机氮的主要竞争长期稳定机制以及DON的形成和结构。将产生关于转移到非微生物、顽固的有机质库的氮的定量数据，从而产生关于通过形成单宁-蛋白质复合体、有机-矿物质结合和非生物氮固定的主要长期稳定过程的相关性的数据。固体15N和13C核磁共振波谱将提供有机N，MALDI-TOF-MS与单宁-蛋白质复合体中单宁的结合形式的信息。化学分解技术可以定量测定大块土壤和有机矿物质复合体中的可水解蛋白质。在研究组的框架内，这一方法将允许区分和量化有机氮与以不稳定形式存在的有机氮的稳定性。最后，这将提供有关植物和微生物之间对氮的竞争的信息，同时考虑到土壤中顽固的有机氮库的形成和缓慢周转。

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.