Accumulation, transformation, and stabilization of organic nitrogen along a mineralogical soil gradient

土壤有机质被认为是生物有效氮的主要来源，但不同功能的有机质池在氮素循环中的作用却知之甚少。该项目旨在强调矿物−有机缔合在新西兰温带雨林时间序列土壤中有机氮(ON)的积累、转化和生物有效性方面的作用。在超过12万年的时间里，土壤在富含硅质的母质(片岩、灰岩)中发育，导致了土壤矿物学和土壤形成的显著梯度。这使得研究土壤矿物学对土壤中氮的积累、化学成分和生物有效性变化的控制，以及土壤矿物学对微生物组成和功能的反馈。为了实现这一目标，我们将(I)表征土壤的矿物组成，(Ii)量化矿物−有机组合中的On含量，(Iii)通过分子生物标记物、X射线光电子和吸收光谱分析各自的形态，(Iv)评估矿物−对N的生物有效性相互作用的后果，以及(V)利用16SRRNA实时聚合酶链式反应和功能基因定量以及酶活性测量来表征参与N循环的微生物群落。这项研究将强调矿物质在土壤循环中的普遍作用，从而为现有的氮素循环模型增添一个重要组成部分。

Soil organic matter is considered the major source of bioavailable N, but the role of functionally different OM pools in N cycling is poorly understood. This project aims at highlighting the role of mineral−organic associations on accumulation, transformation, and bioavailability of organic nitrogen (ON) in soils of a temperate rainforest chronosequence in New Zealand. The soils developed over 120,000 years in silica-rich parent materials (schist, greywacke) giving rise to pronounced gradients in soil mineralogy and soil formation. This allows to study the mineralogical controls on changes in ON accumulation, its chemical composition, and bioavailability as well as the feedbacks of soil mineralogy on microbial composition and function. To reach this goal, we will (i) characterize the mineralogical composition of the soils, (ii) quantify the amount of ON held in mineral−organic associations, (iii) analyse respective ON forms by molecular biomarker, X-ray photoelectron and absorption spectroscopy, (iv) assess the consequences of mineral−ON interactions for N bioavailability, and (v) characterize the microbial communities involved in N cycling using real-time polymerase chain reaction for 16S rRNA and functional gene quantification, and enzyme activity measurements. This study will emphasize the ubiquitous role of minerals in the cycling of soil ON and thus add an important component to current N cycling models.