Key Laboratory of Ecosystem Network Observation and Modeling, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, PR China; Center for Ecosystem Science and Society and the Department of Biological Sciences, Northern Arizona University, Flagstaff, AZ 86011, USA.
Key Laboratory of Ecosystem Network Observation and Modeling, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, PR China; College of Resources and Environment, University of Chinese Academy of Sciences, Beijing 100049, PR China.
Sci Total Environ. 2021 May 15;769:144559. doi: 10.1016/j.scitotenv.2020.144559. Epub 2021 Jan 14.
It is well documented that warming can accelerate greenhouse gas (GHG) emissions, further inducing a positive feedback and reinforcing future climate warming. However, how different kinds of GHGs respond to various warming magnitudes remains largely unclear, especially in the cold regions that are more sensitive to climate warming. Here, we concurrently measured carbon dioxide (CO), methane (CH), and nitrous oxide (NO) fluxes and their total balance in an alpine meadow in response to three levels of warming (ambient, +1.5 °C, +3.0 °C). We found warming-induced increases in CH uptake, decreases in NO emissions and increases in CO emissions at the annual basis. Expressed as CO-equivalents with a global warming potential of 100 years (GWP100), the enhancement of CH uptake and reduction of NO emissions offset only 9% of the warming-induced increase in CO emissions for 1.5 °C warming, and only 7% for 3.0 °C warming. CO emissions were strongly stimulated, leading to a significantly positive feedback to climate system, for 3.0 °C warming but less for 1.5 °C warming. The warming with 3.0 °C altered the total GHG balance mainly by stimulating CO emissions in the non-growing season due to warmer soil temperatures, longer unfrozen period, and increased soil water content. The findings provide an empirical evidence that warming beyond global 2 °C target can trigger a positive GHG-climate feedback and highlight the contribution from non-growing season to this positive feedback loop in cold ecosystems.
有大量文献记载表明，气候变暖会加速温室气体（GHG）排放，进一步引发正反馈，从而加强未来气候变暖。然而，不同类型的 GHG 对不同幅度的变暖如何响应在很大程度上仍不清楚，尤其是在对气候变暖更为敏感的寒冷地区。在这里，我们同时测量了高寒草甸中二氧化碳（CO）、甲烷（CH）和氧化亚氮（NO）通量及其总平衡，以响应三种不同的增温水平（常温、+1.5°C 和+3.0°C）。我们发现，增温导致 CH 吸收增加，NO 排放减少，CO 排放增加。以全球变暖潜势为 100 年的 CO 当量（GWP100）表示，CH 吸收的增加和 NO 排放的减少仅抵消了 1.5°C 增温引起的 CO 排放增加的 9%，而 3.0°C 增温则仅抵消了 7%。CO 排放受到强烈刺激，对气候系统产生了显著的正反馈，而 3.0°C 增温的正反馈更为明显，而 1.5°C 增温则不那么明显。3.0°C 的增温主要通过使土壤温度升高、非冻结期延长和土壤含水量增加，刺激非生长季节 CO 的排放，从而改变了总 GHG 平衡。研究结果提供了一个经验证据，表明超过全球 2°C 目标的变暖会引发温室气体与气候的正反馈，并强调了寒冷生态系统中非生长季节对这一正反馈循环的贡献。
