中国西南岩溶区水分利用效率变化及其对气象要素的响应

水分利用效率（WUE，Water use efficiency）是衡量水资源利用率的重要指标，对气候变化有明显响应，中国西南岩溶区生态缺水严重，水资源利用问题亟需解决，但该区域水分利用效率对气象要素的响应仍不明晰。利用MODIS总初级生产力（Gross primary productivity，GPP）和蒸散发（Evapotranspiration，ET）数据集计算中国西南岩溶区的水分利用效率，结合气象数据和归一化植被指数（NDVI，Normalized difference vegetation index）数据，采用Theil-Sen Median趋势分析和Pearson相关分析，揭示了其水分利用效率的时空变化特征及对气象要素的响应。结果表明：2000-2014年中国西南岩溶区年水分利用效率与植被生长期水分利用效率（AGS-WUE）时间序列变化趋势相近，春、秋季水分利用效率呈上升趋势，夏季呈下降趋势；年水分利用效率呈上升趋势，与降水呈负相关，喀斯特地区与气温呈正相关，非喀斯特地区呈负相关，NDVI增长是主要驱动因素；年水分利用效率和AGS-WUE从东南到西北逐渐升高；非喀斯特地区水分利用效率高于大部分喀斯特地区；总体上高海拔地区水分利用效率高于低海拔地区。气温、海拔及喀斯特发育程度综合影响喀斯特地区水分利用效率。本研究结果能为提高喀斯特生态系统水分利用效率提供理论参考。

Change of water use efficiency and its response to meteorological factors in karst area of Southwest China

Water use efficiency(WUE) is an important indicator to measure utilization ratio of water resources, which has obvious response to climate change. Ecological water shortage is serious in karst area of Southwest China, and water resource utilization problem needs to be solved urgently. However, the response of water use efficiency to meteorological factors is still unclear. In this paper, MODIS gross primary productivity (GPP) and evapotranspiration (ET) data sets were used to calculate water use efficiency in karst area of Southwest China. Combined with meteorological and normalized difference vegetation index (NDVI) data, the temporal and spatial variation characteristics of water use efficiency and its response to meteorological factors were revealed by using the Theil-Sen Median trend analysis and Pearson correlation analysis. The results showed that the change trend of the annual water use efficiency was similar with the active growing season water use efficiency (AGS-WUE) in the karst area of Southwest China from 2000 to 2014. In spring and autumn, water use efficiency demonstrated an upward trend and a downward trend in summer. The annual water use efficiency showed an upward trend, which was negatively correlated with precipitation, positively correlated with temperature in karst areas, while negatively correlated with temperature in non-karst areas. The growth of NDVI was the main driving factor. Annual water use efficiency and AGS-WUE increased gradually from southeast to northwest. The water use efficiency in non karst areas was higher than that in most karst areas. In general, water use efficiency in high altitude areas was higher than that in low altitude areas. Temperature, altitude and the degree of karst development affected water use efficiency in karst areas comprehensively. The results of this study can provide theoretical reference for improving the water use efficiency of karst ecosystem.