大气CO_(2)浓度增加对中国区域植被蒸腾的影响

Effects of Atmospheric CO Concentration on Vegetation Transpiration over China

近几十年来,人类活动带来的化石燃料燃烧和工业过程引起了全球大气CO_(2)浓度的显著增长,带来了一系列生态和环境问题,其中对地表蒸散发的影响就是一个重要方面。地表蒸散发及其分量植被蒸腾是能量和水量平衡的重要组分,直接影响着陆气相互作用和水循环系统。由于大气CO_(2)浓度增加可通过减小叶片气孔导度从而抑制植被蒸腾,为量化这一影响,基于碳水耦合的蒸散发模型PML-V2和CMIP6的大气CO_(2)浓度时空序列驱动数据,分别进行了考虑和不考虑大气CO_(2)浓度逐年增加情况下的2组植被蒸腾模拟试验。通过对比2组结果分析了2001—2014年大气CO_(2)浓度增加对中国区域植被蒸腾的影响。研究结果显示,在季节上,夏季大气CO_(2)浓度增加对植被蒸腾的抑制作用最小,冬季最大;在数量级上,2001—2014年大气CO_(2)浓度引起植被蒸腾变化在0~5%;不同生态系统比较而言,森林、耕地和灌丛生态系统受CO_(2)浓度增加引起植被蒸腾的减小量较大,14年间减小量为15~20 mm/a,而草地下降最小,约5 mm/a;在空间上,我国中东部受影响最大;CO_(2)浓度引起植被蒸腾变化最敏感的区域是我国东南部地区。

In recent decades,a great increase of atmospheric CO_(2)concentration has([CO_(2)])occurred due to fossil fuel combustion and industrialization,which has caused a series of ecological and environmental issues.One of the effects of the increase of[CO_(2)]is on evapotranspiration(ET).ET is a component of surface energy balance and water balance,therefore,its change would influence the exchange between surface and atmosphere and water cycle directly.On the basis of a water-carbon coupled model named PML-V2 and the CMIP6[CO_(2)]datasets,this study estimated two sets of vegetation transpiration(Ec)from 2001 to 2014.One simulation is static:the constant[CO_(2)]concentration in 2001 is fixed as input during the simulation from 2001 to 2014.The other was dynamic:time-varying[CO_(2)]was used during the simulation from 2001 to 2014.By comparing the two sets of Ec,the effects of[CO_(2)]on Ec were explored.The results showed that the reduction in Ec due to the increase of[CO_(2)]was smallest in summer and is largest in winter.From 2001 to 2014,this reduction is 0~5%.The largest effect occurred in the eastern and in the central areas of China.For ecosystems of forest,wetland,cropland and shrubland/savanna,the reduction of Ec due to the increase of[CO_(2)]is 15~20 mm/a till 2014.For grassland,the reduction is 5 mm/a.The sensitivity of the effects of the increase of[CO_(2)]on Ec to arid index,precipitation and air temperature indicated that Ec was the most sensitive to[CO_(2)]in the southeast of China.