金沙江下段植被NDVI变化趋势及其归因

基于MODIS NDVI数据及标准气象站数据、退耕还林资料,辅以空间统计、叠置分析和趋势分析等方法,研究了金沙江下段植被NDVI时空变化特征及其影响因素,结果表明:从年内来看,金沙江下段植被NDVI变化呈单峰型,3月份为最低值0.55,而9月份为最高值0.75,年际上10年以来植被覆盖总体呈现出增长趋势,且这种增长存在显著的空间异质性;研究区植被覆盖较好,植被NDVI平均值为0.65,海拔3 850m以下植被覆盖随海拔上升而增加,超过3 850m后随海拔升高呈降低趋势;年内植被NDVI受降水量的影响较气温更为明显,对两者均有2个月的滞后期,而年际上植被NDVI则受气温变化的影响较降水量更为突出,且大规模的植被恢复工程对金沙江下段植被覆盖的增加有重要贡献。

Study on the relationship between change trend of NDVI and environmental factors in the lower section of Jinsha River, China

Jinsha River is a key area for hydropower construction in China and an ecological barrier of Yangtze River. Based on the temperature and precipitation data from standard meteorological stations and MODIS data, this paper studied the spatiotemporal variation of vegetation NDVI and related influence factors in the lower section of Jinsha River through correlation analysis, spatial statistical analysis, overlay analysis, and other methods. The results showed that during a year, changes of NDVI showed a single peak, with the lowest value at 0.55 in March and the highest value at 0.75 in September. Over the 10 years, the vegetation coverage showed an overall growing trend, with an NDVI growth rate of 0.05%/10a. There was spatial heterogeneity in the NDVI growth. Below 3850-m altitude, the vegetation NDVI generally gradually escalated with altitude, but it declined above 3850-m altitude. During a year, the impact of precipitation on vegetation NDVI was more obvious than that of air temperature, and the NDVI change was two months behind the precipitation and temperature. Over the years, temperature had more prominent influence on vegetation NDVI than precipitation. Besides, the large-scale conversion of farmland to forest had important contribution to the increase of NDVI in the lower section of Jinsha River.