How mycorrhizal types and tree diversity drive soil carbon stabilization.

土壤在土壤有机质（SOM）中储存了大量的碳(C)，这些碳通过聚集体的封闭或矿物表面的吸附而免受微生物分解。根据所考虑的SOM分数的不同，导致SOM的来源有很大差异。颗粒有机质（POM）组分主要由结构组分和植物残体组成，而矿物伴生有机质（MAOM）组分主要来自微生物残体。在温带森林中，树木与真菌（菌根）之间的共生关系对土壤C的储存起着重要作用。与丛枝菌根（AM）林相比，外生菌根（ECM）林的碳储量更高。然而，这些碳储量的稳定性较差，而且有机有机质与净有机质的比值在ECM林中高于AM林。迄今为止，对不同类型的菌根影响POM和MAOM组分中C储量的因素和过程的机制理解仍然缺乏。我们假设菌根类型影响代谢物多样性和根沉积动力学，因此在土壤C稳定中起关键作用。我们认为，在am主导的森林中，少量但持续的高度多样化的根沉积物的输入促进了微生物群落，这随后以MAOM的形式促进了碳的稳定。相反，少而高的碳输入，加上腐养真菌的抑制（Gadgil效应），促进了ECM森林中POM的积累。为了验证这个合作项目的假设，我们将结合一个已建立的树木多样性实验，操纵菌根类型丰度，创新的隔间盆栽实验和最先进的方法，如稳定同位素标记，生物标志物鉴定，液相色谱质谱/质谱。该项目将有助于全面了解温带森林菌根类型驱动的碳周转机制。这就有可能更好地预测森林生态系统中碳储量的未来变化，并制定新的森林管理战略，以维持甚至增加土壤碳储量。

Soils store large amounts of carbon (C) in soil organic matter (SOM), which is protected from microbial decomposition by occlusion in aggregates or by sorption to mineral surfaces. Sources contributing to SOM vary widely depending on the SOM fraction considered. While the particulate organic matter (POM) fraction mainly consists of structural components and plant residues, the mineral-associated organic matter (MAOM) fraction is mainly derived from microbial residues. In temperate forests, the symbiosis between trees and fungi, the mycorrhiza, plays an important role for soil C storage. Forests dominated by trees with ectomycorrhiza (ECM) have higher C stocks compared to forests with arbuscular mycorrhiza (AM). However, these C stocks are less stabilized and the ratio of POM to MAOM is higher in ECM forests than in AM forests. To date, a mechanistic understanding of the factors and processes by which different types of mycorrhiza influence C stocks in POM and MAOM fractions is still lacking. We hypothesize that the mycorrhizal type influences the metabolite diversity and the dynamics of rhizodeposition and consequently plays a critical role in soil C stabilization. We propose that in AM-dominated forests a small but continuous input of highly diverse rhizodeposits promotes microbial communities, which subsequently contribute to increased C stabilization in the form of MAOM. In contrast, an infrequent and high C input, together with a suppression of saprotrophic fungi (Gadgil effect), promotes POM accumulation in ECM forests. To test the hypotheses of this collaborative project, we will combine an established tree diversity experiment that manipulates mycorrhizal type abundances with an innovative compartmented pot experiment and state-of-the-art methods like stable isotope labeling, biomarker identification, and liquid chromatography mass spectrometry/mass spectrometry. The proposed project will contribute to a comprehensive understanding of mycorrhizal type-driven mechanisms of C turnover in temperate forests. This opens the possibility to better predict future changes in C stocks in forest ecosystems and to develop new forest management strategies to maintain or even increase soil C storage.