Peatland Degradation Alters the Microbial–carbon–water Table Interactions that Regulate Carbon Storage

Abstract Peatlands store one-third of global soil carbon while covering only 3% of the world’s land area. Degradation through drainage, grazing, and fire can disrupt the microbial processes that regulate peat decomposition and carbon stabilisation. How these disturbances reshape microbial-carbon-water table interactions remains poorly understood. This study examined how peatland degradation influences microbial community composition and their interactions with peat organic matter chemistry and water table position. Three peatland sites including one degraded and two intact sites on the Bogong High Plains, Australia were studied. Our results demonstrated that microbial communities differed significantly between the three peatland sites and were associated with position relative to the water table, peat carbon chemistry, and depth in the profile. Notably, intact peats retained strong depth and water table dependent heterogeneity in fungal and prokaryotic communities, while these relationships were markedly weaker or absent in degraded peats. In intact peats, fungal and prokaryote community structure was strongly associated with carbon concentration and C:N ratio, while variations in the microbial community structure of degraded peats were more linked to labile and recalcitrant carbon functional groups (alkyl, N-alkyl, O-alkyl, di-O-alkyl, aryl, O-aryl and ketone). Additionally, intact peats had higher prokaryotic diversity and evenness. These findings indicate that peat degradation is associated with altered microbial community composition, carbon functional chemistry and water table position, with likely implications for peatland carbon stability, particularly with continued degradation.