治理塔里木河下游断流河道的生态环境对维护下游整体的生态安全以及巩固近20 a的生态输水成果具有重要意义。塔里木河下游自2000年开始实施生态输水,现今已取得明显成效;但流域内的局部区域生态退化形势严峻,其支流喀然其河和纳胂河河道依然支离破碎。利用河道断流区域遥感影像和气象水文等数据,结合GIS技术和Mann-Kendall非参数检验方法,分析了生态环境要素时空变化规律,评估了其生态安全状况,提出了生态恢复对策。结果表明:(1) 气象要素方面,1971—2019年在大风日数极显著减少的情况下,沙尘暴日数仍有所增加;1957—2019年气温和降水量均呈上升趋势,2000—2018年温度植被干旱指数显著增大。(2) 植被要素方面,2000—2018年植被覆盖度和生产力均呈不显著增加趋势,但其水平均很低;河道断流区生态安全处于预警和中度预警水平。

Harnessing the ecological environment of the cutoff river in the lower reaches of Tarim River is of great significance for maintaining the overall ecological security of the downstream Tarim River and consolidating the achievements of ecological water conveyance in the past 20 years. The lower reaches of Tarim River have been involved in ecological water conveyance since 2000, and now remarkable achievements have been made. However, ecological degradation in some areas of the lower Tarim River Basin is severe, and its branches, the Karanqi River and Nashen River, are still fragmented. Remote sensing images and meteorological and hydrological data of the river cutoff area combined with GIS technology and Mann-Kendall nonparametric test method were used to analyze the temporal and spatial variation laws of ecological environment elements, to evaluate the ecological security situation, and to propose countermeasures for ecological restoration. The results show that in terms of meteorological elements, the number of sandstorm days increased under the condition of extremely significant reduction of gale days from 1971 to 2019, the temperature and precipitation showed an upward trend from 1957 to 2019, and the temperature-vegetation drought index increased greatly from 2000 to 2018. In terms of the variation law of vegetation factors, although the vegetation coverage and productivity showed no significant increasing trend from 2000 to 2018, their levels were very low. Furthermore, the ecological security of the cutoff river area is in the early and moderate warning levels.