毛乌素沙地植被水分利用效率时空变化特征及其 对水热条件的响应

Spatial and temporal change of water use efficiency and its response to air temperature and precipitation in the Mu Us Sandy Land

水分利用效率(WUE)是研究陆地植被生态系统水-碳循环及其耦合关系的重要指标。本文基于MODIS植被总初级生产力(GPP)和蒸散发(ET)数据产品,利用趋势分析和敏感性分析方法,开展了毛乌素沙地2001—2019年植被WUE时空分布特征及对水热条件响应研究。结果表明:①毛乌素沙地2001—2019年GPP、ET均呈显著的线性增加趋势,而植被WUE呈微弱的线性减少趋势。空间上,毛乌素沙地植被WUE以减少趋势为主,占区域总面积的64.53%,集中分布在中西部和南部地区。②不同植被类型WUE中,林地、灌丛WUE呈线性增加趋势,湿地、农田、草地和荒漠呈线性减少趋势。③毛乌素沙地植被WUE对降水敏感性存在阈值效应,阈值为300 mm,即阈值范围内植被WUE随降水增加而增加,超过阈值后,植被WUE随降水增加而下降。

Water use efficiency(WUE)is an important index to study the coupling relationship between water and carbon cycles in terrestrial ecosystems.Based on MODIS data of gross primary productivity(GPP)and evapotranspiration(ET),the temporal and spatial distribution characteristics of WUE and its response to climate change in the Mu Us Sandy Land from 2001 to 2019 are studied.The results show that:①GPP and ET in the Mu Us Sandy Land show a significant linear increasing process from 2001 to 2019,while vegetation WUE showes a weak linear decreasing process.Spatially,the WUE of vegetation in Mu Us Sandy Land is dominated by a decreasing trend,accounting for 64.53%of the total area of the region and concentrated in the central and western and southern regions.②Among the different vegetation types WUE,woodland and scrub WUE show a linear increasing trend,while wetland,farmland,grassland and desert show a linear decreasing trend.③There is a threshold effect on the sensitivity of vegetation WUE to precipitation in the Mu Us Sandy Land,with a threshold value of 300 mm,i.e.the vegetation WUE increases with precipitation within the threshold value,and decreases with precipitation after the threshold value is exceeded.