Mycorrhiza-mediated distribution of particulate and mineral-associated organic carbon across global forests

The stabilization of soil organic carbon (SOC) in forest ecosystems is crucial for mitigating climate change. However, the interaction of mycorrhizal associations with environmental factors to influence SOC fractions globally remains poorly understood. Here, we synthesize 2,784 observations from 234 peer-reviewed studies to examine global patterns of particulate (POC) and mineral-associated organic carbon (MAOC) in forests dominated by arbuscular (AM) versus ectomycorrhizal (ECM) forests. Our results reveal that ECM forests possess 24% higher POC content and exhibit greater sensitivity to climate warming than AM forests. In contrast, AM forests sustain higher MAOC content, which shows less variability across climate gradients. Linear mixed-effects models indicate distinct responses of POC and MAOC to the interactive effects of mycorrhizal type and environmental drivers. Notably, POC content in ECM forests increases with stand age. While young AM forests contain higher levels of both POC and MAOC, middle-aged and mature ECM forests surpass AM forests in POC, with no significant difference in MAOC. Using existing data, we project global changes in these SOC fractions and propose a mycorrhiza-informed framework for forest carbon sequestration. Our findings underscore the pivotal role of mycorrhiza-environment interactions in SOC partitioning and stabilization, offering critical insights for refining global carbon models and guiding climate-smart forest management.