Anaerobic environment shaped by flooding gradient and its regulatory effect on soil carbon stability and microbial carbon allocation in glacier meltwater wetlands

This study provides new evidence on how glacier meltwater-induced flooding gradients regulate soil carbon stabilization in alpine wetlands through anaerobic environments and microbial carbon allocation. Its novelty lies in linking hydrological change, soil carbon fractions, microbial necromass carbon (MNC), extracellular polymeric substances (EPS), and microbial community assembly within a unified mechanistic framework. In particular, we demonstrate that seasonal flooding preferentially promotes MNC accumulation, whereas perennial flooding enhances EPS production, revealing distinct microbial pathways of carbon stabilization under different anaerobic conditions. This advances current understanding beyond bulk SOC responses by showing how hydrological shifts reshape both carbon fractionation and microbial contributions to carbon persistence. The study is of clear international relevance because glacier-fed wetlands are widespread yet climate-sensitive ecosystems in mountain regions worldwide, and their carbon sink function is increasingly threatened by ongoing cryospheric change. Our findings therefore provide broadly relevant insights into wetland carbon sequestration, soil–microbe–hydrology interactions, and the vulnerability of alpine carbon sinks under global climate change.