Carbon cycling in peatlands A review of processes and controls

Covering only 3% of the land area, northern peatlands store about 30% of the global soil carbon and account for 5 to 10% of the global methane burden to the atmosphere. A review of the literature on net ecosystem exchange, net primary productivity, carbon mineralization, methane emissions, and dissolved organic carbon dynamics indicates that peatlands can be both C sources and sinks. The temporal and spatial variability of fluxes is large, but a substantial portion of this variation can be explained by environmental and ecological variables. Uncertainty in predictions about carbon dynamics under changing environmental conditions arises from a number of knowledge gaps: (i) the understanding of how organic matter is mineralized and partitioned into carbon dioxide, methane, and dissolved organic carbon is insufficient; (ii) little is known about the consequences of long-term and short-term disturbances, such as elevated carbon dioxide concentrations, nitrogen and sulfur deposition, fire, and droughts, on the individual components of the carbon cycle; (iii) models that capture the dynamic interaction of the processes and their controls have not been developed yet, with the notable exception of methane dynamics.