Drought and Shrub Encroachment Accelerate Peatland Carbon Loss Under Climate Warming.

Peatlands store substantial amounts of carbon (C) in the form of peat, but are increasingly threatened by drought and shrub encroachment under climate warming. However, how peat decomposition and its temperature sensitivity () vary with depth and plant litter input under these stressors remains poorly understood. We incubated peat from two depths with different degrees of decomposition, either alone or incubated with divinum shoots or ovalifolia leaves, under five temperature levels and two moisture conditions in growth chambers. We found that drought and addition increased CO emissions in both peat layers, while affected only shallow peat. Deep peat alone or with exhibited higher than pure shallow peat. Drought increased the of both depths' peat, but this effect disappeared with fresh litter addition. The CO production rate showed a positive but marginal correlation with microbial biomass carbon, and it displayed a rather similar responsive trend to warming as the microbial metabolism quotient. These results indicate that both deep and dry peat are more sensitive to warming, highlighting the importance of keeping deep peat buried and waterlogged to conserve existing carbon storage. Additionally, they further emphasize the necessity of moss recovery following vascular plant encroachment in restoring carbon sink function in peatlands.