Precipitation increase promotes soil organic carbon formation and stability via the mycorrhizal fungal pathway

Changes in soil organic carbon (SOC) stocks play a pivotal role in regulating future climate change. Arbuscular mycorrhizal fungi (AMF) are critical regulators of SOC dynamics, yet the impacts of climate-induced changes, such as precipitation increase (Pi), on AMF- and root-mediated SOC formation and stability remain largely unexplored. Combining global meta-analysis with a long-term field experiment, our study demonstrates that Pi enhances SOC formation and stability primarily through AMF, rather than plant roots, by recruiting bacterial K-strategists and promoting necromass production. These findings provide direct evidence that AMF-driven microbial processes are essential for SOC stability under changing precipitation regimes, uncovering an often-overlooked mechanism of SOC sequestration in grassland ecosystems and enhancing our understanding of climate change impacts on C cycling.