Forest mycorrhizal types mediated environmental controls on global particulate and mineral-associated organic matter storage

Abstract

Most trees associate with arbuscular mycorrhizal (AM) or ectomycorrhizal (ECM) fungi, which increases the input to soil carbon pools. Identifying the regulatory mechanisms of mycorrhizal fungi on environmentally controlled global forest total SOM storage is crucial for understanding the global carbon cycle and addressing climate change. Currently, we lack a comprehensive understanding of how mycorrhizae regulate forest total SOM storage, especially regarding POM and MAOM. This study is based on published data and aims to elucidate the regulatory role of different mycorrhizal types on environmentally controlled POM and MAOM storage by analyzing data from 81 AM to 124 ECM forest sites worldwide. The dataset included 718 sets of organic matter fractions (POM, MAOM, total SOM), climate factors (MAT, MAP-PET), soil factors (pH, sand, silt, clay), and matter inputs (i.e., net primary production [NPP]). We used variance partitioning analysis (VPA), stochastic gradient boosting, and path analysis in R to assess the relative importance of these variables. Significant differences in total SOM storage between AM and ECM forests were found, primarily due to variations in MAOM storage. AM forests store more MAOM (8.41 g C kg⁻¹ soil) and total SOM (8.20 g C kg⁻¹ soil) than ECM forests. In ECM forests, climate and soil explained a higher proportion of variation in POM, MAOM, and total SOM storage (40.06–46.70 %) compared to AM forests (17.56–31.20 %). Further analysis indicates that MAOM storage in AM forests is strongly influenced by Clay (21.90 %) and NPP (20.20 %), whereas in ECM forests, it is predominantly affected by MAT (42.90 %) and MAP-PET (23.90 %). In global forest ecosystems, climate and soil are the primary controlling factors, with different mycorrhizal types mediating variations in POM and MAOM storage, which in turn indirectly affect total SOM storage.