Effects of tree mycorrhizal type on ecosystem carbon stock in a subtropical mountainous forest

1. Tree mycorrhizal associations could significantly affect forest carbon (C) stock. Although extensive research has been primarily conducted in temperate forest ecosystems, our understanding of how mycorrhizal types influence ecosystem C in subtropical forests, where arbuscular mycorrhizal (AM) and ectomycorrhizal (ECM) trees co-occur with varying dominance levels, is still limited.2. Fifty-eight forest plots covering a natural gradient of ECM tree dominance (ECM%, calculated as the percentage of total basal area of ECM trees vs. all trees) were selected in a subtropical mountain forest. The plant, litter, and soil properties were determined, and we investigated the relationships between ECM% and forest C stock (tree biomass C, forest floor C, and soil C) and their regulate mechanisms.3. The total forest C stock ranged from 15.57 to 38.93 Kg C m-2, and increased with ECM tree dominance. Specifically, tree biomass C and forest floor C stock accounted for 47.13% and 3.43% of the total forest C storage, respectively, and exhibited a positive relationship with ECM tree dominance. Soil C stock accounted for 49.44% of the total forest C storage but showed no significant relationship with ECM tree dominance. The increase in tree biomass C with ECM tree dominance was linked to the higher density of large-size trees, whereas the higher forest floor C was mainly associated with lower litter quality. However, the larger vegetation C pool and litter C pool in plots with high ECM tree dominance did not lead to a greater soil C stock4. Our findings highlight the role of tree mycorrhizal type on ecosystem C stock in subtropical forests. Understanding these relationships is crucial for formulating effective C sequestration strategies to mitigate climate change.