增温对青藏高原高寒草甸呼吸作用的影响

生态系统呼吸(ER)和土壤呼吸(SR)是草地生态系统碳排放的关键环节,其对气候变化极为敏感。高寒草甸是青藏高原典型的草地生态系统,其呼吸作用对气候变化的响应对区域碳排放具有重要的影响。以高寒草甸生态系统为对象,于2012—2016年采用模拟增温的方法研究呼吸作用对增温的响应。结果表明:增温对高寒草甸ER的影响存在年际差异,2013年和2014年增温对ER无显著影响,其他年份显著增加ER(P0.05),综合5年结果,平均增幅达22.3%。增温显著促进了高寒草甸SR(P0.05),较对照处理5年平均增幅高达67.1%;增温总体上提高了SR在ER中的比例(P0.05),最高增幅达到59.9%。ER和SR与土壤温度有显著的正相关关系(P0.05),与土壤水分没有显著的相关关系(P0.05)。对照样地中,土壤温度分别能解释33.0%和18.5%的ER和SR变化。在增温条件下,土壤温度可以解释20.5%和13.0%的ER和SR变化。在增温条件下,SR的温度敏感性显著增加,而ER的温度敏感性变化较小,导致SR的比重进一步增加。因此,在未来气候变暖条件下,青藏高原高寒草甸生态系统碳排放,尤其是土壤碳排放有可能进一步增加,土壤碳流失风险增加。

Effects of warming on respiration in alpine meadow in the Qinghai-Tibetan Plateau

Ecosystem respiration(ER)and soil respiration(SR)are key components of grassland ecosystem carbon emissions and are extremely sensitive to climate change. Alpine meadow is one of the main grassland types on the Qinghai-Tibet Plateau and its response to climate change has an important influence on regional carbon emission. In this paper, we conducted in situ warming experiment to investigate the response of ecosystem respiration and soil respiration to warming in an alpine meadow in the Qinghai-Tibetan Plateau from 2012 to 2016. The results showed that there was the interannual variability of the warming effects on ER in the alpine meadow. In 2013 and 2014, warming had no significant effects on ER, but warming significantly increased ER in other years (P<0.05). Five-year average of ER and SR increased by 22.3% and 67.1%, respectively, under warming compared to control. The proportion of SR in ER increased significantly under warming relative to control (P<0.05), and the highest increase reached 59.9%. ER and SR were positively correlated with soil temperature (P<0.05), not soil moisture (P>0.05). In control plots, soil temperature explained variations of ER and SR by 33.0% and 18.5%, respectively. Under warming, the soil temperature explained variations of ER and SR by 20.5% and 13.0%. Under warming, the temperature sensitivity of SR increased significantly, while the temperature sensitivity of ER have no significant change. Overall, the carbon emissions and soil carbon loss may increase in the future climate warming scenario in alpine meadow ecosystems on the Qinghai-Tibet Plateau.