Arbuscular mycorrhizal fungi mediated biotic carbon pump in alpine meadows of the Qinghai Tibetan Plateau under a warming and wetting climate: patterns and mechanism.

Climate warming accompanied by an overall increase in precipitation has reshaped hydrothermal regimes in many alpine meadows on the Qinghai-Tibetan Plateau, with important implications for soil organic carbon (SOC) dynamics. However, precipitation trajectories are spatially heterogeneous across alpine meadow regions, and the direction and mechanisms underlying SOC responses to warming-wetting conditions remain uncertain. While traditional frameworks emphasize plant litter inputs, emerging evidence highlights the central role of microbial processes in SOC stabilization. Arbuscular mycorrhizal fungi (AMF), which are widely distributed in alpine meadow ecosystems, mediate plant-derived carbon (C) transfer into soils and may regulate SOC formation, turnover, and stabilization. This review synthesizes current knowledge on how warming and increased precipitation influence SOC stocks and dynamics in alpine meadows, with a focus on AMF-mediated mechanisms. We highlight how AMF regulate belowground C inputs, priming effects, and microbial metabolism, thereby affecting SOC accumulation and stabilization. Evidence indicates that warming and altered precipitation jointly modify SOC turnover by influencing plant-AMF C allocation, AMF community composition, microbial C use efficiency, and enzyme activities. These responses are strongly context dependent.We propose an AMF-mediated biotic C pump (BCP) under warming and wetting, emphasizing the role of AMF in promoting the incorporation and stabilization of newly fixed C in soils. This framework advances understanding of C cycling and improves predictions of ecosystem feedbacks to climate change.