Nonlinear response of ecosystem respiration to multiple levels of temperature increases

Global warming exerts profound impacts on terrestrial carbon cycles and feedback to climates. Ecosystem respiration (ER) is one of the main components of biosphere CO2 fluxes. However, knowledge regarding how ER responds to warming is still lacking. In this study, a manipulative experiment with five simulated temperature increases (Control, Warming 1, Warming 2, Warming 3, Warming 4) was conducted to investigate ER responses to warming in an alpine meadow on the Tibetan Plateau. The results showed that ER was suppressed by warming both in dry and wet years. The responses of ER to warming all followed a nonlinear pattern. The nonlinear processes can be divided into three stages, including the quick-response stage (W1), stable stage (W1–W3) and transition stage (W4). Compared with the nonlinear model, the linear model maximumly overestimated the response ratios of ER to warming 2.2 % and 3.2 % in 2015 and 2016, respectively, and maximumly underestimated the ratio 7.0 % and 2.7 %. The annu...