Different Responses of Soil Respiration and Its Components to Experimental Warming with Contrasting Soil Water Content

Abstract

Soil water content (SWC) regulation on the responses of soil respiration (Rs ), autotrophic respiration (Ra ), and heterotrophic respiration (Rh ) to warming are rarely investigated in alpine meadow ecosystem in the Qinghai-Tibet Plateau (QTP). We conducted a warming experiment to investigate how SWC regulates the responses of Rs and its components (Ra and Rh ) to warming. Infrared heaters were used to simulate climatic warming. Soil respiration was measured inside surface collars (2–3 cm deep) and Rh was measured inside deep collars (50 cm deep), which excludes root respiration. Autotrophic respiration was calculated by subtracting Rh from Rs . Warming increased the average Rs and Rh by 9.9% and 12.7% but had no significant effect on Ra . Interaction between warming and SWC had significant effect on Rs and its components. Soil respiration and Ra decreased by 5.8% and 36.3% in dry conditions, but they increased by 23.5% and 47.7% in wet conditions. Growing season above-ground biomass was enhanced by 0.1 kg m-2 in wet conditions but reduced by 0.10 kg m-2 in dry conditions under warming manipulation. The estimated net ecosystem carbon (C) balance was 0.65 and -0.16 kg m-2 in wet and dry conditions, respectively, which indicates a net C emission of alpine meadow in wet but a net C sequestration in dry conditions. Our results emphasize the importance of incorporating SWC in simulation of ecosystem carbon balance under a warming climate.