基于关键指标的黄河流域近20年生态系统质量的时空变化

黄河流域生态系统质量直接关系到国家中长期生态安全和高质量发展，研究黄河流域生态系统质量时空变化，可为黄河流域的生态保护和高质量发展提供参考. 基于长时间序列MODIS数据，提取能够反映生态系统质量的归一化植被指数(NDVI)、叶面积指数(LAI)、表层水分含量指数(SWCI)和陆地表面温度(LST)4个关键指标构建遥感生态指数(remote sensing ecological index, RSEI)，结合Sen+Mann-Kendall检验和Hurst指数，分析黄河流域2000—2018年生态系统质量变化情况及变化趋势. 结果表明:2000年、2010年、2018年3个年份RSEI与各指标的平均相关系数为0.856，均高于各指标之间的平均相关系数，RSEI能够综合反映黄河流域生态系统质量. 近20年黄河流域生态系统质量存在局部改善与退化并存的现象，其中改善面积占52.84%，主要分布在湟水谷地、黄土高原、鄂尔多斯高原、河套平原和宁夏平原；退化面积占18.48%，主要分布在黄河源区、陕西关中盆地和黄河下游. Hurst指数分析表明，黄河源区生态系统质量未来呈改善趋势，黄土高原持续性改善和未来退化趋势并存，鄂尔多斯高原、阴山南麓、子午岭以未来变化不确定为主，陕西关中盆地以持续性退化为主，生态系统质量未来变化趋势不确定和持续性退化的区域仍需要持续关注. 研究显示，基于关键指标的遥感生态指数能够综合反映黄河流域生态系统质量状况，近20年黄河流域生态系统质量改善面积占52.84%，远高于退化面积(18.48%)，且黄河源区生态系统质量未来以改善为主. 

Spatial and Temporal Changes of Ecosystem Quality Based on Key Indicators in Yellow River Basin from 2000 to 2018

The ecosystem quality of the Yellow River Basin is directly related to the China's mid- and long-term ecological security and high-quality development. The study on the temporal and spatial variation of the ecosystem quality of the Yellow River Basin can provide reference for ecological protection and high-quality development in the Yellow River Basin. In this paper, the changes and trends of the ecosystem quality in the Yellow River Basin from 2000 to 2018 were analyzed by using the normalized difference vegetation Index (NDVI), leaf area index (LAI), surface water content index (SWCI) and land surface temperature (LST) retrieved from long-time series MODIS data to construct the remote sensing ecological index (RSEI), combined with the Sen+Mann-Kendall test and the Hurst index. The results showed that the average correlation coefficient between RSEI and each index was 0.856 in 2000, 2010 and 2018, which was higher than the average correlation coefficient between each indicator, and could well reflect the ecosystem quality profile. The ecosystem quality of the Yellow River Basin was high in the west and southeast, but low in the north, which was consistent with the spatial distribution pattern of the ecosystem. In the past 20 years, there was a coexistence of local improvement and degradation of ecosystem quality in the Yellow River Basin. The improved area accounts for 52.84%, which was mainly distributed in the Huangshui Valley, the Loess Plateau, Ordos Plateau, Hetao Plain and Ningxia Plain. The degraded area accounts for 18.48% and was mainly distributed in the source area of the Yellow River, the Guanzhong Basin of Shaanxi and the lower Yellow River. The results of the Hurst index indicate that the ecosystem quality of the Yellow River Basin will strongly reverse sustainability. The quality of the ecological environment in the source area of the Yellow River will show an improvement trend in the future, continue improvement and the degradation trend will coexist in the Loess Plateau in the future, and there is uncertain in the Ordos Plateau, the southern foot of the Yinshan Mountain and the Ziwuling Mountains in the future. It will continue to degradate in the Guanzhong Basin of Shaanxi. These regions with uncertain changes and continuous degradation of ecosystem quality in the future need to be focused upon and further researched. Our studies have shown that the remote sensing ecological index based on key indicators can synthesize the quality of the ecosystem of the Yellow River Basin. The improvement area of the ecosystem quality was 52.84% in the Yellow River Basin in the past 20 years, which was much higher than the degraded area (18.48%), and the ecosystem quality of the Yellow River source area will be mainly improved in the future.