Differential responses of ecosystem respiration components to experimental warming in a meadow grassland on the Tibetan Plateau

Abstract

Global warming is anticipated to have profound effects on terrestrial carbon fluxes and thus feed backs to future climate change. Ecosystem respiration (Reco) is one of the dominant components of biosphere CO2 fluxes, but the effects of warming on Reco are still unclear. A field warming experiment using open top chambers (OTCs) was conducted in a meadow grassland on the Tibetan Plateau to study the effects of warming on the components of Reco. Warming significantly enhanced above-ground plant respiration (Ragb) and total autotrophic plant respiration (Rplant) by 28.7% and 19.9%, respectively, but reduced heterotrophic respiration (Rh) by 10.4%. These different responses resulted in the insensitive responses of Reco and soil respiration (Rs) to the experimental warming. The warming treatment also increased Rplant/Reco and Ragb/Reco by 8.4% and 17.3%, respectively, while decreasing Rh/Reco by 19.0%, suggesting that warming could eventually cause Reco to be dominated by Rplant. Enhancements in Rplant and Ragb were related to the warming-induced increases in aboveground biomass (AGB) while reduced Rh was closely coupled with warming-induced decrease of microbial biomass carbon. Our results highlight that the differential responses of the components of Reco to different environmental physics under warming scenarios should be taken into consideration to project the future carbon-climate feed backs.