How mycorrhizal types and tree diversity drive soil carbon stabilization.

土壤中储存了大量的碳(C)在土壤有机质(SOM)中，通过在团聚体中的封闭或通过吸附到矿物表面来防止微生物分解。对土壤有机质有贡献的来源因考虑的土壤有机质组成而有很大不同。颗粒有机质(POM)组分主要由结构成分和植物残留物组成，矿质相关有机质(MAOM)组分主要来自微生物残留物。在温带森林中，树木与真菌、菌根之间的共生对土壤碳的储存起着重要的作用。与丛枝菌根(AM)林相比，以外生菌根(ECM)林木为主的森林具有更高的碳储量。然而，这些C种群的稳定性较差，ECM林的POM/MAOM比AM林高。到目前为止，对于不同类型的菌根影响POM和MAOM馏分中的碳库的因素和过程仍然缺乏机械上的了解。我们推测，菌根类型影响着土壤中代谢产物的多样性和根际沉积的动态，因此在土壤碳稳定中起着关键作用。我们认为，在AM占优势的森林中，少量但持续的高度多样化的根际沉积物的输入促进了微生物群落，从而有助于以MAOM的形式增加碳的稳定性。相反，低频率和高C输入，加上腐生真菌的抑制(Gadgil效应)，促进了ECM森林中POM的积累。为了验证这一合作项目的假设，我们将结合已建立的操纵菌根类型丰度的树木多样性实验、创新的隔室盆栽实验和最先进的方法，如稳定同位素标记、生物标记物鉴定和液-质联用/质谱仪。拟议的项目将有助于全面了解温带森林中碳周转的菌根型驱动机制。这为更好地预测森林生态系统碳储量的未来变化和制定新的森林管理战略以维持甚至增加土壤碳储量提供了可能性。

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.