FIGURE 7.

Overview of changing C stocks, flows, and key ecosystem properties across permafrost thaw gradient. While standing stocks of C in plant biomass decrease across the permafrost thaw gradient, the rate of C cycling increases. This is driven by increased uptake (NPP) and faster transfer of NPP to SOM via litter with thaw (as seen in fully thawed fen versus palsa or bog areas). High bioavailability of litter in the fully thawed fen results in rapid decomposition with a large contribution to CO₂ and especially CH₄ production but the high volume of litter input results in incomplete decomposition. In pre‐thaw (palsa) areas, high bioavailability but smaller volume of litter and aerobic conditions result in near‐complete decomposition of inputs but a smaller contribution to C emissions than in post‐thaw areas. In intermediate thaw (bog) areas, the intermediate volume of low bioavailability litter and anaerobic conditions result in slower and incomplete decomposition with intermediate C emissions. Overall, this leads to positive feedback from permafrost thaw to global warming