Dynamic Monitoring of Vegetation Coverage in Three Gorges Reservoir Area Based on MODIS NDVI | 基于MODIS NDVI的三峡库区植被覆盖度动态监测

صينى. 基于MODIS―NDVI遥感数据,采用像元二分模型估算三峡库区2000―2009年的年最大植被覆盖度,并在像元尺度上分析库区年最大植被覆盖度的时空变化规律及其驱动力。结果表明：三峡库区大部分区域处于高植被覆盖度,并随高程和坡度的增加而增大,其中年最大植被覆盖度大于60%的区域占92.35%;近10年来,库区年最大植被覆盖度总体呈微弱上升趋势,其中呈显著增加或降低趋势的像元数仅占7.16%,在20个区县中石柱、江津和丰都的植被覆盖度存在退化风险;降水是影响库区植被覆盖度年际波动的主导因子,当年5―8月降水量与年最大植被覆盖度的相关性最高,但在空间上存在差异,其中呈显著正相关区域主要分布于库区西部低山丘陵农业种植区,该区域降水增加有利于植被生长,而部分高海拔地区的年最大植被覆盖度与降水呈显著负相关,过多降水反而会抑制植被生长。

إنجليزي. Using a dimidiate pixel method, the annual maximum vegetation coverage in Three Gorges Reservoir Area （TGRA） from 2000 to 2009 was estimated based on the MODIS NDVI remote sensing data. Furthermore, the temporal-spatial variation and its driving force of annual maximum vegetation coverage were analyzed at pixel scale. The results showed that the annual maximum vegetation coverage was high in the most area of TGRA, and approximate 92% of the whole area had the annual maximum vegetation coverage greater than 60%. The annual maximum vegetation coverage increased with the increasing of elevation and slope. In recent 10 years, annual vegetation coverage of the whole area showed a weak increasing trend. The pixels with significant increase or decrease in the annual maximum vegetation coverage were only 7.16% of total pixels, and the vegetation coverage of Shizhu, Jiangjin and Fengdu had high degradation risk out of the total 20 counties. Precipitation was the dominant driving factor for annual fluctuation of vegetation coverage in TGRA. The annual maximum vegetation coverage was notably related to the accumulated precipitation from May to August. However, there was obvious spatial difference in the correlation. The significant positive correlation pixels mainly distributed in the western hilly farmland in TGRA, where the increase of precipitation can promote the vegetation growth. The precipitation was considerably negatively correlated with the vegetation coverage at the higher sea levels in the northeastern part of TGRA.