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

土壤有机质被认为是生物可利用氮的主要来源，但不同功能的有机质库在氮循环中的作用尚不清楚。该项目旨在强调新西兰温带雨林土壤中有机氮（on）积累、转化和生物利用度中矿物-有机关联的作用。土壤在富含硅的母质（片岩、灰岩）中发育了12万年，在土壤矿物学和土壤形成方面产生了明显的梯度。这可以研究矿物学对氮积累、化学组成和生物利用度变化的控制，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)表征土壤的矿物学组成，（ii）量化矿物-有机结合中氮的含量，（iii）通过分子生物标志物、x射线光电子和吸收光谱分析各自的氮形式，（iv）评估矿物-氮相互作用对氮生物利用度的影响。(v)利用实时聚合酶链反应（real-time polymerase chain reaction）对16S rRNA和功能基因进行定量分析，以及酶活性测量，表征参与氮循环的微生物群落。本研究将强调矿物质在土壤氮循环中的普遍作用，从而为现有的氮循环模型增加一个重要的组成部分。

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.