Declined microbial stability in the active layer under alpine permafrost degradation contributes to carbon loss

Permafrost degradation has become more extensive and potentially leads to massive soil carbon loss under climate warming. However, soil microbial-mediated mechanism for carbon loss of the active layer remains unclear in the permafrost regions. Here, we investigated how soil microbial communities in the active layer respond to permafrost degradation and influence carbon storage in alpine ecosystems of the Qinghai-Tibet Plateau. Results reveal that alpine permafrost degradation reduces bacterial and archaeal richness, declines microbial community stability as evidenced by the increased sensitivity of microbial communities to environmental changes, and by its higher network interconnections and centrality, and lower robustness. Moreover, every 10% enlarging microbial richness decreases organic carbon density by 1.9-2.8%, even accelerated at 0.1-1.5% by microbial dissimilarity increase in severely-degraded permafrost, but not in lightly-degraded permafrost. Overall, our study demonstrates declined microbial stability in the active layer under permafrost degradation, with critical implications for carbon-climate feedbacks in alpine ecosystems.