Role of inter-specific ectomycorrhizal fungal diversity for forest ecosystem nutrition

本项目的主要目标是描述外生菌根真菌的种间多样性，在磷获取和循环生态系统中的磷吸收和树木营养。在本项目的第一阶段，它表明，P形态的垂直分布表现出不同的模式和浓度在不同的土壤深度，我们的研究地点。这些结果表明，磷的分布是决定机制的磷供应的植被。在这个更新的建议，我们计划研究是否以及如何磷的形式和磷的可用性结构的真菌群落的分类和功能组成。我们将解决以下假设：（i）真菌群落（腐生真菌或菌根真菌）的功能组成根据土壤层表现出垂直梯度。我们建议，功能相似性较高的O-地平线比在A-地平线的网站与对比P的可用性。细根及其相关的菌根在O层是重要的P供应在P贫网站导致高P循环，而那些在A层在P丰富的网站促进P收购。为了验证这一建议，我们将研究垂直真菌剖面（宏基因组分析），并通过土壤交换实验测试功能差异。对于根相关真菌的功能分析，将应用磷吸收成像。(ii)磷有效性的变化引起真菌群落的分类和功能的变化。这一假设将通过应用P，N和N × P在磷贫和磷丰富的森林网站进行测试。我们预计，氮的应用也影响了菌根群落的结果，磷的可用性。(iii)磷的吸收和转运到主机的外生菌根真菌与最近的光合同化物的供应进行调节。为了验证这一假设，将进行环剥实验。

The main goal of this project is to characterize the inter-specific diversity of ectomycorrhizal fungi for P uptake and tree nutrition in P acquiring and recycling ecosystems. In the first phase of this project, it was shown that the vertical distribution of P forms exhibited contrasting patterns and concentrations in different soil depths of our study sites. These findings suggest that the distribution of P is decisive for the mechanism of P supply to the vegetation. In this renewal proposal we plan to study whether and how P forms and P availability structure the taxonomic and functional composition of the fungal communities. We will address the following hypotheses:(i) the functional composition of the fungal communities (saprophytic or mycorrhizal fungi) shows a vertical gradient according to soil layers. We propose that the functional similarity is higher in the O-horizons than in A-horizons of sites with contrasting P availability. Fine roots and their associated mycorrhizas in the O layer are important for P supply at the P poor site leading to high P recycling, whereas those in the A horizon at the P rich site foster P acquisition. To test this suggestion we will study the vertical fungal profiles (metagenome analysis) and test functional differences by soil exchange experiments. For functional analyses of root associated fungi, imaging of P uptake will be applied.(ii) Changes in P availability induce taxonomic and functional changes of the fungal communities. This hypothesis will be tested by application of P, N and N x P in P-poor and P-rich forest sites. We expect that N application also influences P availability with consequence for the mycorrhizal communities.(iii) P uptake and translocation to the host is regulated by the supply of the ectomycorrhizal fungi with recent photo-assimilates. To test this hypothesis, girdling experiments will be conducted.