Tree diversity effects on rhizodeposition and rhizosphere priming: the role of the mycorrhizal colonization in coupling C and N cycles in diverse tree stands

大多数温带树种主要与丛枝菌根（AM）或外生菌根（ECM）真菌相关联，这些真菌为它们的宿主提供矿物营养以交换碳。由于这两种菌根类型在养分经济方面存在根本差异，因此建议它们提供与森林中碳（C）循环和养分保持相关的土壤地球化学转化的综合指数。然而，鲜为人知的是，在树木多样性生态系统功能关系的菌根类型的组特定的作用。本研究项目的主要目的是确定不同AM和ECM乔木林分根际碳通量和土壤氮循环的功能组差异。在关键的土壤地球化学过程中，我将重点放在根系分泌和分解，这代表了微生物引发效应的原因和影响，以刺激土壤有机质的养分释放。假设的有机营养经济的ECM的立场的基础上，我假设，增加根系分泌物是一个主要的机制，ECM树木维持生产力在不同的立场，而不同的AM看台主要取决于落叶对散装土壤过程的影响。为了实现这个项目的目标，我将联合收割机一个既定的树多样性实验，操作菌根类型的丰度与创新和超越国家的最先进的生态和生态生理学的方法，辅以3-D激光消融断层扫描，固态13 C-CPMAS核磁共振光谱，和代谢组学。该项目将完善一个概念模型，说明菌根类型在树木多样性对土壤功能的影响方面的作用，以便纳入全球模拟模型。

The majority of temperate tree species associates predominantly with either arbuscular mycorrhizal (AM) or ectomycorrhizal (ECM) fungi, which provide mineral nutrients to their host in exchange for carbon. Since the two mycorrhizal types differ fundamentally in their nutrient economy they were suggested to provide an integrated index of biogeochemical transformations relevant to carbon (C) cycling and nutrient retention in forests. Yet little is known about the group-specific role of the mycorrhizal type in the tree diversity–ecosystem functioning relationship. The central aim of this research project is to determine functional group differences in rhizosphere C fluxes and soil nitrogen cycling between diverse AM and ECM tree stands. Among the key biogeochemical processes I will focus on root exudation and decomposition, which represent cause and effect of the microbial priming effect to stimulate nutrient release from soil organic matter. On the basis of the assumed organic nutrient economy of ECM stands, I hypothesize that increased root exudation is a primary mechanism by which ECM trees sustain productivity in diverse stands, while diverse AM stands mainly depend on leaf litter effects on bulk soil processes. To achieve the objectives of this project I will combine an established tree diversity experiment that manipulates mycorrhizal type abundances with innovative and beyond state-of-the-art ecological and ecophysiological methods that are complemented by 3-D laser ablation tomography, solid-state 13C-CPMAS nuclear magnetic resonance spectroscopy, and metabolomics. This project will refine a conceptual model on the role of the mycorrhizal type in tree diversity effects on soil functions for the incorporation in global simulation models.