2001-2018年西江流域水分利用效率时空变化及影响因素

目的]探究气候变化形势下流域的碳循环和水循环相互关系，对流域的水资源科学配置有重大意义。方法]以西江流域为例，基于2001—2018年GLASS产品中的初级生产力(GPP)和蒸散发(ET)数据，定量计算区域生态系统植被水分利用效率(WUE),利用趋势分析和偏相关分析的方法研究植被WUE时空演变特征及其影响因素。结果]2001—2018年西江流域植被的WUE总体呈增加趋势；林地的WUE增长速率最快，草地次之，耕地最慢。从空间分布来看，WUE值从广西中部的耕地向四周逐渐升高，WUE低值还零星分布在云南东部的台地和丘陵地区；西江流域15.23%,12.12%的区域WUE分别与气温、降水呈显著正相关；11.54%的区域WUE与太阳辐射呈显著负相关；NDVI与WUE具有显著正相关性；WUE随海拔的上升呈上升—平缓—上升的趋势，在2 100 m左右，WUE出现明显波动。结论]气候因子、NDVI、海拔、人类活动均不同程度影响西江流域植被的水分利用效率，本研究可为西南喀斯特地区石漠化治理和流域生态防护林体系的建设提供参考。

Spatiotemporal Variation of Water Use Efficiency and Its Influencing Factors in Xijiang River Basin from 2001 to 2018

Objective]Exploring the interrelationship between the carbon and water cycles in watersheds in the context of global climate change has significant implications for the scientific allocation of water resources in watersheds. Methods] Xijiang River Basin was taken as an example, the water use efficiency(WUE)of regional ecosystem vegetation was quantified based on gross primary productivity(GPP)and evapotranspiration(ET)data in GLASS products from 2001 to 2018, then the spatial and temporal evolution characteristics of WUE and its influencing factors were studied by using the methods of trend analysis and partial correlation analysis. Results] The WUE of vegetation in Xijiang River Basin generally showed an increasing trend from 2001 to 2018. The WUE of forest land grew at the fastest rate, followed by grassland and the slowest by cropland. In terms of spatial distribution, WUE values gradually increased from cultivated land in central Guangxi to the surrounding areas, and low WUE values also sporadically distributed in the tablelands and hilly areas in the eastern of Yunnan. WUE values in 15.23% and 12.12% of the area of Xijiang River Basin were significantly and positively correlated with temperature and precipitation, respectively. WUE in 11.54% of the area of Xijiang River Basin was significantly and negatively correlated with solar radiation. NDVI was significantly and positively correlated with WUE; WUE with the rise of the altitude showed a rising-flat-rising trend, and at altitude of around 2 100 m, there is a significant fluctuation of WUE. Conclusion] The above results indicate that climate factors, NDVI, altitude and human activities all affect the water use efficiency of Xijiang River Basin to different degrees. This study can provide reference for the management of stone desertification in the southwest karst region of China and the construction of ecological protection forest system in the basin.