The National Basic Research Program of China (973 Program)
格尔木作为青藏高原重要的交通枢纽城市，其生态环境的可持续发展关系到该地区的经济繁荣与社会稳定。利用长时间序列的研究在节点选择方面缺少指向性，通常采用等间隔划分的方法来确定研究时间节点。基于此，通过Google Earth Engine （GEE）平台计算了格尔木近30年（1990-2019年）的遥感生态指数（RSEI），并使用非参数统计方法——Mann-Kendall突变检验，科学的确定研究的时间节点，再进一步分析格尔木生态环境时空变化并探讨其影响因素。研究表明：（1） RSEI可以有效地评价格尔木生态环境质量，30年间RSEI均值从0.38下降至0.33，生态环境整体呈退化趋势；（2）由突变检验确定1990、2001、2006、2015、2019年为研究的时间节点。各年份RSEI以较差为主，占总面积的45%以上，主要分布在柴达木盆地北部。RSEI等级变化以下降为主，2001年下降最为明显，2015年有所减缓；（3）受气候与人类活动不同程度的影响，格尔木RSEI变化趋势以下降为主，占区域总面积的89.73%，广泛分布在柴达木地区和唐古拉山地区，受气候因素影响较大；而变化趋势上升的仅占3.24%，主要分布在格尔木人类活动密集的市区、乡镇以及柴达木盆地成矿带，受人类活动影响较大。
As an important transportation hub city in the Qinghai-Tibet Plateau, Golmud's sustainable and healthy development of the ecological environments is closely related to the local economic prosperity and social stability of the related regions. Most studies on ecological change monitoring with long-time sequence remote sensing imageries often ignore the directivity in the selection of key time nodes among the long time series, and they usually take methods such as equal interval partition to select time nodes. Based on the above situation, we first calculated the 30 year sequence data of Remote Sensing Ecological Index (RSEI) of the city of Golmud on the Google Earth Engine (GEE) platform and we scientifically defined the time nodes of the study area by a nonparametric statistical method, the Mann-Kendall mutation test method, and then further analyzed the temporal and spatial variation characteristics of the ecological environment in the city of Golmud and in the end discussions were carried out to find out the main influencing driving factors. The results showed that, (1) the index of RSEI could be used to effectively evaluate the quality of ecological environments in the city of Golmud and similar areas. The average value of RSEI in the past 30 years was gradually changed from 0.38 to 0.33, and the overall changing trend of ecological environment was degradation; (2) through the Mann-Kendall mutation test, the year nodes of 1990, 2001, 2006, 2015 and 2019 were selected as the final time nodes of the study area. For the above five time nodes, the grades of the index of RSEI are mainly in the state of poor, accounting for more than 45% of the total area of Golmud, and the regions with the state of poor were mainly distributed in the northern part of the Qaidam Basin. The changing trend of the grade of the RSEI index was mainly decreased during the whole time series, which was most obvious in the time node of 2001 and the changing trend began to slow down in 2015; (3) affected by the climate and human activities at different degrees, the changing trend of the RSEI index in Golmud was mainly decreasing, which accounted for 89.73% of the total area, and which was widely distributed in the Qaidam and Tanggula Mountains areas, was greatly affected by climate factors; While areas with increasing trend took only 3.24% of the total area. The areas with increasing changing trend of the RSEI index were mainly distributed in the urban and town areas with intensive human activities in the city of Golmud, and the metallogenic belt of Qaidam Basin, which were greatly affected by human activities.