基于MODIS NDVI的长江中游区域植被动态及与气候因子的关系

基于1999-2015年的MODIS NDVI时间序列遥感数据,应用趋势分析、变异系数、重标极差分析和偏相关分析等方法,分析了长江中游的植被时空变化特征及其与气象因子的关系。结果表明,长江中游地区NDVI均值总体上呈上升趋势（从0.72增加到0.80）。从空间分布来看,NDVI低值区域（0.1-0.5）占1.40%,高值区域（>0.7）占87.15%;NDVI空间格局呈"西高东低、北高南低"的分布特征,低值区域表现为以三省省会城市为中心向外辐射。Hurst指数显示,研究区大部分区域（60.54%）的NDVI变化趋势具有不确定性,持续性改善区域（34.78%）主要分布在西部山地区,持续性退化区域（3.26%）主要分布在人类活动频繁的较发达城市区域。在年际尺度上,研究区NDVI与各气象因子关系均不显著;月际尺度上,NDVI与降水、相对湿度和日照时数显著相关,降水和日照时数有明显的时滞性。区域内NDVI动态趋势以不确定性发展为主,城市群周边NDVI呈现持续退化的区域应该引起关注。

Vegetation dynamics and its relationship with climate factors in the middle reaches of the Yangtze River Based on MODIS NDVI

The middle reaches of the Yangtze River (including Hubei, Hunan, and Jiangxi Province) and the "Central Triangle City Grop" are located in the center of the Yangtze River Economic Belt and are one of the key national ecological secrity areas. The dynamic change of vegetation is affected by geographical environment and climate change, which is closely related to the future regional sustainable development. Based on MODIS NDVI time series remote sensing data from 1999 to 2015, the paper analyzed the dynamic characteristics of vegetation and its relationship with climatice factors in the middle reaches of the Yangtze River from 1999 to 2015 by applyingtrend analysis, coefficient of variation, rescaled range analysis, and partial correlation analysis, etc. The results showed that the average value of NDVI in the middle reaches of the Yangtze River showed an overall upward trend (increased from 0.72 to 0.80). From the perspective of spatial distribution, the low-value area of NDVI (0.1-0.5) was 1.40%, and the high-value area (>0.7) accounted for 87.15%, overall pattern of NDVI was high in the west and and north region and low in the east and south region. The low-value areas were radiated outward from the capital cities of the three provinces. Based on hurst index, the changing trend of NDVI was uncertain in most areas (60.54%) of the study area. The continuous improvement area (34.78%) was mainly distributed in the western mountain area, and the continuous degradation area (3.26%) was mainly distributed in the more developed urban areas with frequent human activities. On the interannual scale, no significant relationship between the NDVI and the meteorological factors were observed. From the correlation between vegetation and climate factors, the relationship between NDVI and meteorological factors was not significant on the interannual scale; on the monthly scale, precipitation, relative humidity and sunshine hours were the main factors affecting NDVI change, and precipitation and sunshine hours had obvious time lag; on the spatial correlation, the area of positive correlation between vegetation change and temperature and precipitation was larger than that of negative correlation, and the area of positive correlation with relative humidity was larger than that of negative correlation The area with negative correlation to humidity and sunshine hours was larger than that with positive correlation. The dynamic trend of NDVI in the middle reaches of the Yangtze River was mainly uncertain, and the regions around the urban agglomerations showing continuous degradation of NDVI should be concerned.