气候变化对亚高山暗针叶林土壤温室气体排放的影响

Effects of climate change on soil greenhouse gas emissions in subalpine dark coniferous forest

利用生物地球化学模型Forest-DNDC模拟气候变化对贡嘎山亚高山暗针叶林土壤温室气体的释放的影响。以位于贡嘎山东坡海拔3000m的峨眉冷杉(Abies fabri)中龄林为研究对象,以1999-2006年8年的日气候数据进行平均得到的日平均最高温度、日平均最低温度和日平均降水总量作为基线(Base)气候情景,另外设置了温度+2℃(T+)、温度-2℃(T-)、降水量+20%(P+)、降水量-20%(P-)、温度+2℃同时降水量+20%(T+P+)、温度-2℃同时降水量-20%(T-P-)、温度+2℃同时降水量-20%(T+P-)、温度-2℃同时降水量+20%(T-P+)8种气候变化情景。结果显示:贡嘎山峨眉冷杉林土壤CO2释放随着温度增加而增加,土壤N2O释放对降水量改变敏感,而土壤NO的释放对温度和降水的改变均比较敏感,二者表现为协同作用。温度+2℃同时降水量+20%(T+P+)情景下土壤CO2释放最高,高于基线情景的36.08%;温度-2℃同时降水量+20%(T-P+)情景下土壤CO2释放最低,低于基线情景的36.89%。土壤N2O释放随着降水量的增加而升高,随着降水量减少而降低;温度和降水量同时增加时土壤NO释放均高于单一增加温度或降水量情景,而温度和降水量同时降低时土壤NO释放均低于单一降低温度或降水量情景。

The biogeochemical Forest-DNDC model was used to derive estimates of the effects of climate change on soil greenhouse gas emissions in the subalpine dark coniferous forest ecosystem of Gongga Mountain. The subalpine dark coniferous forest is middle age Abies fabri forest which is located 3 000 m altitude on the eastern slope of Gongga Mountain. Daily average maximum and minimum air temperature, daily average sum of precipitation which calculated from 8-year dataset each today’s climate from 1999 to 2006 were assumed as the base scenario. The following were designed as 8 different climate change scenarios： 2 ℃ increase （T＋） and decrease （T-） in daily air temperature; 20% increase （P＋） and decrease （P-） in daily precipitation; 2 ℃ increase in temperature and 20% increase in precipitation （T＋P＋）; 2 ℃ decrease in temperature and 20% decrease in precipitation （T-P-）; 2 ℃ increase in temperature and 20% decrease in precipitation （T＋P-）; 2 ℃ decrease in temperature and 20% increase in precipitation （T-P＋）. The simulated results showed that soil CO2 emissions were relatively sensitive to changes in temperature （T）, while N2O emissions were more sensitive to precipitation （P） changes and NO emissions were found to be sensitive to both temperature and precipitation changes within the ranges of observed climate variability. The largest positive and negative responses of soil CO2 emissions to climate change occurred under T＋P＋ scenario （36.08% higher than that of the base scenario） and T-P＋ scenario （36.89% lower than that of the base scenario）. Soil N2O emissions increased under elevated daily precipitation and decreased under reduced daily precipitation. Increase in both air temperature and precipitation resulted in a greater magnitude of soil NO emissions than the individual increase in either air temperature or precipitation alone. And decrease in both air temperature and precipitation resulted in a lower magnitude of soil NO emissions than the individual decrease in either air temperature or precipitation alone.