西北地区草地水分利用效率时空特征及其对气候变化的响应

Spatio-temporal characteristics of grassland water use efficiency and its response to climate change in northwest China

【目的】研究中国西北地区水分利用效率(WUE)时空动态及其对气候变化的响应,为该地区水资源合理利用及生态环境建设提供依据。【方法】运用气温、降水以及云量等数据驱动LPJ模型(Lund-Potsdam-Jena dynamic global vegetation model),模拟出净初级生产力(net primary production,NPP)、蒸散发(evapotranspiration,ET)等数据,估算1961-2013年西北地区草地WUE,研究该区域草地生态系统WUE的时空动态及其对气候变化的响应。【结果】①1961-2013年西北地区草地NPP年均值为199.72 g/m^2,ET年均值为233.22 mm。二者在整体上呈东南向西北递减的空间变化趋势;②1961-2013年西北地区草地多年平均WUE为0.61 g/(mm·m^2)。随着时间变化,西北地区草地WUE表现出显著上升趋势;③西北地区草地WUE与气温、降水量均呈显著正相关,尽管气温升高、降水量增加都对WUE的增加产生影响,但是温度比降水对草地WUE的影响更大。【结论】中国西北地区草地WUE空间分布自东向西呈递减趋势,并随时间变化呈显著增加趋势,气候变化对WUE影响显著,WUE随气温的升高以及降水的增多而增加。

【Objective】The dynamic changes of water use efficiency(WUE)in northwest China and its response to climate change are important to simulate the changing trends of the WUE under future climate change,which could provide a basis for water resources utilization and ecological environment construction in this region.【Method】The net primary productivity(NPP)and evapotranspiration(ET)data were simulated by the Lund-Potsdam-Jena dynamic global vegetation model(LPJ model)using air temperature,precipitation,cloud cover,and other data from northwest China during 1961-2013.The spatio-temporal dynamic changes of the grassland WUE and its response to climate change were then analyzed via correlation analysis and other methods.【Result】①The average annual NPP value of the grassland was199.72 g/m^2 in northwest China from 1961 to 2013,and the average annual ET value was 233.22 mm.The changes of the NPP and ET showed a spatial decreasing trend from southeast to northwest,and the changes of the NPP and ET for the grassland showed significant upward trends during this period.②The average WUE per unit area of grassland was 0.61 g/(mm·m^2)in northwest China from 1961 to 2013.The spatial distribution of the grassland WUE showed a decreasing trend from the east to the west in northwest China,while the grassland WUE in the northwestern region showed a significant upward trend during the past decades.③The grassland WUE in the northwestern China was positively correlated with the air temperature and precipitation,and the positive correlation was dominant.The WUE of the grassland increased significantly with the increase of air temperature and precipitation,and the impacts of air temperature on the grassland WUE was greater than those of precipitation.【Conclusion】The spatial distribution of WUE for the grassland in northwest China decreased from the east to the west.However,the WUE increased significantly,which was highly correlated with climate change and the WUE might increase with the increase of air temperature and precipitation increasing.