Origin and composition of organic N forms and related stabilization mechanisms in a soil chronosequence

本项目旨在研究天然雨林土壤中有机氮（N）的稳定机制，特别强调矿物控制。它基于夏威夷群岛（美国）的“长基底老化梯度”年代序列，该年代序列涵盖了300至4.1 × 106年的基底年龄，其他环境变量相当恒定。这允许跟踪有机氮积累和稳定性的变化，与矿物成分有关，在土壤形成过程中发生变化。该提案涉及以下方面：（i）通过蛋白质组学、生物标志物分析和酶活性测量，分析了有机氮在土壤层的体积和粘土级组分中的积累以及不同年龄地点的有机氮转化，（二）通过将矿物相变量和有机质性质与有机质的组成联系起来，研究矿物与有机质对氮素保存的控制作用。有机氮，揭示了湿化学方法和X射线吸收近边结构（N-XANES），和（iii）本地化，浓度和组成的稳定的有机氮形式使用降解技术。最后，我们测试在批量吸附和培养实验中，如果（iv）吸附与矿物相的N化合物的相互作用可以解释所观察到的模式的有机N的积累，转化和稳定。我们期待新的见解的起源和土壤中有机氮形态的稳定机制。

This project aims at the mechanisms of organic nitrogen (N) stabilization in native rainforest soils with special emphasis on the mineralogical control. It bases on the `long substrate aging gradient¿ chronosequence at Hawaiian Islands (USA) that covers substrate ages from 300 to 4.1 × 106 years at otherwise fairly constant environmental variables. This allows to track changes in organic N accumulation and stabilization as related to mineral composition, which changes during soil formation. The proposal addresses the following aspects: (i) accumulation of organic N forms in bulk and clay-size fractions of soil horizons and transformation of organic N across the differently aged sites as analysed by proteomics, biomarker analysis, and enzyme activity measurements, (ii) investigation of the mineralogical vs. organic matter control on N preservation by relating mineral phase variables and organic matter properties to the composition of organic N, as revealed by wet chemical methods and X-ray absorption near edge structure (N-XANES), and (iii) localization, concentration, and composition of stabilized organic N forms using degradation techniques. Finally we test in batch sorption and incubation experiments if (iv) sorptive interaction of N compounds with mineral phases can account for the observed patterns of organic N accumulation, transformation, and stabilization. We expect novel insight into origin and stabilization mechanisms of organic N forms in soil.