Differential responses of ecosystem respiration components to experimental warming in a meadow grassland on the Tibetan Plateau
The Tibetan plateau is experiencing a higher than average increase in air temperature, rendering the ecosystems more vulnerable and sensitive. The alpine meadow grassland is one of the most widespread vegetation types in this region. The Tibetan Plateau also contains a great amount of global soil carbon, prompting researches in understanding how ecosystem carbon exchange will respond to rising temperature. However, how ecosystem respiration (Reco) and its source components will respond to warming are still not clear. In this study, a field experiment was conducted in a meadow grassland by using open top chambers to study the warming effects on Reco and its components.
Warming had no significant effect on Reco, soil respiration (Rs), and root respiration (Rb). However, warming significantly enhanced aboveground plant respiration (Ra) and total autotrophic respiration (Rp) by 28.7% and 19.9%, respectively, but reduced heterotrophic respiration (Rh) by 10.4%. Warming also profoundly increased Rp/Reco and Ra/Reco by 8.4% and 17.3%, respectively, but decreased Rh/Reco by 19.0%. Soil moisture played critical roles for warming effects on Reco and its components. Enhanced Rp was highly related to the higher temperature and warming-induced AGB, while reduced Rh was closely coupled with warming-induced decrease of soil moisture and microbial biomass carbon. Our results highlight that Reco and Rs could be insensitive to warming due to differential responses of their components to warming-induced changes in soil temperature and moisture. The differential responses of Reco components to different environmental physics under warming should be taken into consideration to project the future carbon-climate feedbacks.