2000—2018年黄河流域生长季植被指数变化及其对气候因子的响应

黄河流域位于我国干旱、半干旱地区，生态环境脆弱，探究其植被指数变化和对气候因子的响应对该地区生态建设具有重要意义。基于黄河流域2000—2018年MODIS归一化植被指数、增加型植被指数和气象数据，利用最大值合成法、趋势分析和相关分析等方法，分析了两种植被指数的时空变化特征及受气候因子的影响机制，探讨了NDVI与EVI在反映植被变化和对气候因子响应的差异。结果表明：2000—2018年，黄河流域地区植被NDVI、EVI分别以0.059/10a、0.038/10a的变化率增加，空间上以显著改善为主，面积占比分别为77.13%和75.27%,大多分布在1000—1500 m海拔处，中游地区改善较为良好，林地改善率最高。显著退化区域较小，主要分布在巴颜喀拉山西北部、西宁市、银川市、包头市、呼和浩特市、太原市、西安市及关中盆地和洛阳市周边，建设用地退化率最高。在生长季期间，植被指数变化与气温和降水以正相关为主，气温滞后时间为1个月，降水滞后时间为3个月，都为草地最为相关；与辐射之间为负相关，滞后时间为3个月，其中林地最为相关。在0.05显著性检验水平下，驱动黄河流域生长季植被变化的主要气候因子...

Changes of NDVI and EVI and their responses to climatic variables in the Yellow River Basin during the growing season of 2000-2018

The Yellow River Basin is located in the arid and semi-arid area of China, which ecological environment is fragile. The researches about vegetation index changes and its response to climate factors were significant to the ecological construction of the region. Based on the MODIS normalized difference vegetation index (NDVI), enhanced vegetation index (EVI) and meteorological data, we mainly used Maximum Value Composite (MVC), trend analysis, and partial correlation analysis to explore the characteristics of the spatio-temporal changes of vegetation cover and driving mechanism of climatic factors in the Yellow River Basin from 2000 to 2018. At the same time, the differences between the NDVI and EVI reflected variations of vegetation and their responses to climatic factors were discussed. Results showed that the temporal change rate of NDVI and EVI in the Yellow River Basin increased at 0.059/10 a and 0.038/10 a, respectively. In terms of space, the main areas significantly improved, accounting for 77.13% and 75.27% of the area, respectively. Most of them were distributed at 1000-1500 m elevations, and the middle reaches have improved well. The improvement rate of forest land was higher than that in other areas. The degraded areas were relatively rare and mainly distributed in the northwestern Bayan Qula Mountain, Xining City, Yinchuan City, Baotou City, Hohhot City, Taiyuan City, Xi''an City, the Guanzhong Basin and the surrounding areas of Luoyang City. The degradation rate of construction land was higher compared with other areas. During the growing season, the change of vegetation index (VI) was positively correlated with air temperature and precipitation, the lag time of air temperature in the VI was one month, while in precipitation the lag time were three months. Among them, grassland showed the most significantly positive correlation. There was a negative correlation between radiation and vegetation index, and the time lag was about 3 months, among which the most relevant area was in forest land. At the significant level of 0.05, the precipitation and radiation driven the vegetation change during the growing season in the Yellow River Basin. On the whole, precipitation had a great influence on the change of vegetation in this area. In terms of temporal and spatial changes, the NDVI was more sensitive to vegetation change than EVI, and had a higher correlation with precipitation and radiation in the Yellow River Basin.