Responses of ecosystem respiration to short-term experimental warming in the alpine meadow ecosystem of a permafrost site on the Qinghai-Tibetan Plateau

As the largest high-altitude permafrost region in the world, the Qinghai-Tibetan Plateau (QTP) has experienced pronounced warming, which may exert a profound effect on ecosystem's CO2 emissions due to the large amounts of organic carbon in the permafrost soil. In this study, response of ecosystem respiration to short-term experimental warming was investigated in the alpine meadow ecosystem of a permafrost site on the QTP during the 2012 growing season. The results showed that cumulative growing season ecosystem CO2 emissions were 277.09 and 32533 g C m(-2) for the control and warming plots, respectively. Thus, a 2.18 degrees C increase in ground surface temperature and a 0.62 degrees C increase in soil temperature prompted a 17.41% increase in the ecosystem's CO2 emissions. The relationships between temporal variations in ecosystem respiration and soil temperature can be described through exponential equation. Soil temperature accounted for 50 and 64% of the variations in ecosystem respiration on a diurnal scale, and 71 and 84% of the variations in ecosystem respiration on a seasonal scale in the control and warming plots, respectively. Moreover, the temperature sensitivity (i.e. apparent Q(10) values) of the ecosystem respiration rates was significantly higher in the warming plots than in the control plots. Our results indicate that the effect of warming promoted CO2 emissions of the alpine meadow ecosystem at a permafrost site on the QTP, and that soil temperature is the key factor controlling ecosystems' CO2 emissions. In addition, while ecosystem respiration provides positive feedback on the rise in temperature through an increase in temperature sensitivity under warming conditions, at least in the short term, this feedback may be partially offset by an increase in above- and belowground biomass caused by warming. (C) 2015 Elsevier B.V. All rights reserved.