Negative responses of ecosystem autotrophic and heterotrophic respiration to experimental warming in a Tibetan semi-arid alpine steppe

摘要

Evaluating the responses of ecosystem respiration (Re) and its components to climate change is crucial for predicting terrestrial carbon cycling, particularly for the alpine grassland ecosystems. However, effects of climatic warming on ecosystem heterotrophic respiration (Rh) and autotrophic respiration (Ra) remain poorly understood in semi-arid alpine grasslands. A field manipulative experiment was conducted to investigate the effects of experimental warming on total Re, Rh and Ra in a Tibetan semi-arid alpine steppe during growing seasons of 2013 and 2014. Our results showed that warming decreased seasonal Re, Rh and Ra by 29%, 37% and 13%, respectively. However, warming tended to increase the contribution of Ra to Re (Ra/Re) but decrease that of Rh to Re (Rh/Re). Negative responses of Re was closely related to the changes in plant biomass and soil microbial biomass carbon. The apparent Q(10) values of Ra were higher than those of Re and Rh, with the Q(10) values ranked as Ra > Re > Rh. Warming decreased the apparent Q(10) values of Re and the two components. Our results emphasize that Re and its components respond negatively to experimental warming, and soil carbon loss has the potential to be less under future climatic warming in the Tibetan semi-arid alpine steppe.