Effects of experimental warming on soil respiration and its components in an alpine meadow in the permafrost region of the Qinghai-Tibet Plateau

摘要

The response of soil respiration (R-s) and its components (autotrophic [R-a] and heterotrophic respiration [R-h]) to climate warming is one of the uncertainties in ecosystem carbon (C) models. Here we conducted a warming experiment in an alpine meadow dominated by Koresbia in the permafrost region of the Qinghai-Tibet Plateau (QTP) to examine effects of warming on R-s and its components. Infrared heaters were used to simulate a 2 degrees C warming of the surface soil temperature. Deep collars (50 cm to exclude root growth) were inserted into soil to measure R-h: R-a, which was calculated by subtracting R-h from R-s. Average R-s and its components (R-a and R-h) were significantly stimulated by 21.5, 27 and 15.6%, respectively, in warmed plots from January 2011 to October 2013. The contribution of R-h to R-s decreased in the warmed plots because of the smaller relative increase in R-h than in R-a. Annual soil C release increased by 263 and 247 g C m(-2) in 2011 and 2012, respectively. Stimulation in R-a and R-h was related to the significant increase in root biomass (0-50 cm) and in labile soil C in the deeper layer (40-50 cm). The temperature sensitivities (Q(10)) of R-s and its components all increased with larger values in R-a, followed by R-s and R-h. Our results suggest a positive feedback between soil C release and climatic warming in the permafrost region of the QTP.