How mycorrhizal types and tree diversity drive soil carbon stabilization.

• Applicants: Professorin Dr. Ina Christin Meier; Professorin Dr. Johanna Pausch
• Subject Area: Soil Sciences
• Term: since 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 517857572

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.

• DFG Programme: Research Grants