Effects of Experimental Warming on Growing Season Temperature and Carbon Exchange in an Alpine Tundra Ecosystem

Abstract— Accurate assessing CO2 exchange of tundra ecosystems is essential for better understanding and prediction of the CO2 responses of tundra ecosystems to climate change. In this study, the effects of warming on growing season CO2 exchange in an alpine tundra ecosystem were examined with closed transparent chamber attached to an infrared gas analyzer. Compared to ambient controls, open-top chambers (OTCs) increased growing season air (15 cm above ground surface) and soil (10 cm in depth) temperature by 1 and 0.2°C, respectively. Compared to the controls, OTCs tended to increase the plant height of Dryas octopetala and Vaccinium uliginosum by 15.1% (but P > 0.05) and 7.5% (P > 0.05), respectively. During the growing season, OTC-warming increased net ecosystem CO2 exchange by 136% and gross ecosystem exchange by 63%, whereas no significant difference in ecosystem respiration was found. Our results suggest that the predicted air warming will increase ecosystem carbon uptake of the Changbai Mountain alpine tundra during growing season. However, there is an uncertainty about the net CO2 exchange of that ecosystem at an annual scale, because, due to the inaccessibility, we did not study the winter respiration. Further studies are, therefore, needed to estimate the annual and long-term trade-off between CO2 uptake and emission in that region.