Vegetation and climate controls on potential CO2, DOC and DON production in northern latitude soils

Abstract Climatic change may influence decomposition dynamics in arctic and boreal ecosystems, affecting both atmospheric CO 2 levels, and the flux of dissolved organic carbon (DOC) and dissolved organic nitrogen (DON) to aquatic systems. In this study, we investigated landscape‐scale controls on potential production of these compounds using a one‐year laboratory incubation at two temperatures (10° and 30 °C). We measured the release of CO 2 , DOC and DON from tundra soils collected from a variety of vegetation types and climatic regimes: tussock tundra at four sites along a latitudinal gradient from the interior to the north slope of Alaska, and soils from additional vegetation types at two of those sites (upland spruce at Fairbanks, and wet sedge and shrub tundra at Toolik Lake in northern Alaska). Vegetation type strongly influenced carbon fluxes. The highest CO 2 and DOC release at the high incubation temperature occurred in the soils of shrub tundra communities. Tussock tundra soils exhibited the next highest DOC fluxes followed by spruce and wet sedge tundra soils, respectively. Of the fluxes, CO 2 showed the greatest sensitivity to incubation temperatures and vegetation type, followed by DOC. DON fluxes were less variable. Total CO 2 and total DOC release were positively correlated, with DOC fluxes approximately 10% of total CO 2 fluxes. The ratio of CO 2 production to DOC release varied significantly across vegetation types with Tussock soils producing an average of four times as much CO 2 per unit DOC released compared to Spruce soils from the Fairbanks site. Sites in this study released 80–370 mg CO 2 ‐C g soil C −1 and 5–46 mg DOC g soil C −1 at high temperatures. The magnitude of these fluxes indicates that arctic carbon pools contain a large proportion of labile carbon that could be easily decomposed given optimal conditions. The size of this labile pool ranged between 9 and 41% of soil carbon on a g soil C basis, with most variation related to vegetation type rather than climate.