Permafrost Carbon Quantities and Fluxes

Abstract

The permafrost soil and ecosystem carbon storage is the net result of carbon uptake from the atmosphere or water by photosynthesis, and organic matter decomposition by respiration of ecosystem organisms. In this chapter, the ecosystem and soil carbon balance are treated in more detail. First, the basic components of the ecosystem carbon balance are discussed. Recent quantifications of the permafrost carbon store, and how the ecosystem carbon balance contributed in the past to these carbon stores, is reviewed. The processes of carbon decomposition in soils are discussed, with emphasis on the effects of changes in the soil environment that affect decomposition rates. Anaerobic conditions created by high water tables are an important component of carbon preservation in permafrost soils next to low temperatures. Redox processes in soils, and ecosystem methane emission therefore are emphasized. Organic carbon decomposition in soils also releases its nutrients. Slow decomposition of organic matter is an important factor contributing to nutrient limitation in permafrost ecosystems; nevertheless, leaks in the nutrient cycle may occur which result in emission of the strong greenhouse gas N2O. The chapter concludes with an overview of measurement methods of carbon fluxes, and the magnitude of these fluxes in various permafrost ecosystems.