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

由于对植物、菌根真菌、土壤微生物和土壤有机质中氮的固存之间的分配的不完全理解，我们对森林土壤中氮竞争的认识是混乱的。采用田间和实验室研究相结合的方法，结合15N标记实验，阐明有机N的主要竞争性长期稳定机制以及DON的形成和结构。定量数据将产生的氮转移到非微生物，顽固性有机物质池，因此，主要的长期稳定过程的相关性，通过单宁-蛋白质复合物的形成，有机-矿物结合和非生物N固定。固体15N和13C核磁共振光谱将提供有机N结合形式的信息，MALDI-TOF-MS在单宁-蛋白质复合物中与单宁结合。化学分解技术将允许量化散装土壤和有机-矿物复合体中的可水解蛋白质。在研究小组的框架内，这种方法将允许区分和量化有机氮与不稳定形式存在的有机氮的稳定性。考虑到土壤中顽固性有机氮库的形成和缓慢周转，这将为植物和微生物之间对氮的竞争提供信息。

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.