水分利用效率（Water use efficiency,WUE）是研究陆地碳水循环耦合的一种常用度量指标。基于MODIS的总初级生产力（GPP）和蒸散发（ET）数据,通过Slope趋势分析和敏感性分析等方法,研究了中亚WUE的时空变化规律及其对气候因子与干旱的动态响应。结果表明：（1） 2000—2018年,中亚年均WUE随着生境湿润程度的增加而升高（生长期规律与此相反）,其中湿地WUE最高（1.820±0.10 g C·mm^-1·m^-2）,而灌丛WUE最低（1.330±0.18 g C·mm^-1·m^-2）。（2） 中亚WUE呈略微下降趋势,每年下降速率为0.016 g C·mm^-1·m^-2,年均WUE的显著下降区域大于上升区域。WUE对年降水和年气温的敏感性均表现为正值区大于负值区且均存在阈值效应,降水敏感性阈值介于250~300 mm（低值点）和500~550 mm（高值点）,温度阈值介于3~6 ℃（高值点）和9~12 ℃（低值点）,且ε_NDVI（WUE对NDVI敏感性系数）与降水变化呈正相关关系,与气温变化呈负相关关系。（3） 通过WUE与标准化降水指数（SPEI）的相关性比较,发现WUE受干旱程度影响由大到小依次为灌丛、作物、森林、草原和湿地,且不同植被类型下WUE随着干旱程度的增加而升高。

Water use efficiency (WUE) is a commonly used measurement index for studying the coupling of the terrestrial carbon cycle and hydrological cycle. Using gross primary productivity and evapotranspiration of MODIS data, we assessed the spatial-temporal variation law of WUE in Central Asia and its dynamic response to climate factors and drought through the slope trend analysis approach, sensitivity analysis, among others. We found the following results. (1) From 2000 to 2018, the WUE mean value greatly fluctuated with habitat humidity increment (i.e., the growth period is contrary to the law). In contrast, its maximum value (1.82±0.10 g C·mm^-1·m^-2) was basically in the wetland region and its minimum value (1.33±0.18 g C·mm^-1·m^-2) in the shrubland. Generally, the WUE value is on a slight downward trend with an annual descending rate of 0.016 g C·mm^-1·m^-2. (2) The areas with WUE mean value on the significant downward trend were found greater than those on the significant rising trend. Furthermore, the sensitivity of WUE toward precipitation and air temperature both illustrated the areas with positive values to be greater than those with negative values. The sensitivity coefficient toward normalized difference vegetation index (ε_NDVI) showed a positive correlation with precipitation variation but negatively correlated with air temperature change. The sensitivity of WUE toward precipitation and air temperature both exist threshold effect with the range between 250-300 mm (low-value point) and 500-550 mm (high-value point) of precipitation sensitivity. Besides, the fittest temperature threshold of WUE variation ranged from 3-6 ℃ (low-value point) to 9-12 ℃ (high-value point). (3) WUE of grassland with abundant trees, mixed forest, and open shrub was positively correlated with standardized precipitation index (SPEI), with a correlation coefficient of 0.83, 0.81, and 0.70, respectively. On the other hand, the WUE of grassland with deciduous needle-leaf forest and permanent wetland was lowly correlated with SPEI, with a correlation coefficient of -0.35, -0.22, and 0.02, respectively. WUE is affected by the degree of drought and evolved in a descending way under shrub, crops, forest, grasslands, and wetlands while ascending with the drought degree increment under different vegetation types. The influence of drought degree toward WUE value on different habitats ranked in descending order (shrub, crop, forest, grassland, and wetland) but elevated with the increment in drought degree with different vegetation types.