Effects of Deeper Snow on Ecosystem CO2 Fluxes in Tussock Tundra in Northern Alaska

Climate warming in northern latitudes is projected to lead to increased precipitation and, therefore, increased snow depth in arctic ecosystems. Deeper snow in winter can affect these ecosystems by leading to warmer soils, shorter growing seasons, and increased water availability to plants after snow melt, with subsequent implications to ecosystem biogeochemical cycling. Increases in snow depth in the arctic have been reported to lead to changes in plant community composition and, particularly, increases in shrub abundance in tundra ecosystems. Because of the confounded effects of greater snow depth on arctic ecosystems, it is unclear what the mechanisms underlying observed shrub cover changes are. In this study, we investigated the differential effects of greater snow depth on ecosystem CO2 exchange in tussock tundra near Toolik Lake, Alaska. We measured CO2 uptake and ecosystem respiration throughout the growing season after the first winter of snow depth manipulation and compared these results to CO2 exchange in plots under long-term (14 years) snow depth increase. Our initial findings indicate that long-term increases in snow result in greater relative increases in respiration as opposed to ecosystem photosynthesis, leading to greater net CO2 efflux. However, in the first year of snow additions, these differences were not observed, nor were there any differential effects of winter warming only, or winter warming with added water on CO2 exchange.