三峡库区（重庆段）植被覆盖变化分析及评价

Analysis and Evaluation of the Vegetation in the Three Gorges Reservoir Region(Chongqing Section)

为分析三峡库区(重庆段)植被及植被变化,利用2000-2015年MODIS 3级归一化植被指数16日合成产品MOD13A1,分析了长江沿线重庆段22区县植被指数的时空分布特征及变化趋势,结果表明:(1)在三峡库区蓄水后,长江沿线的植被表现为向好趋势,植被生长环境也有所改善,长江沿线东部地区,植被好转尤为明显。(2)距河道越远的区域,植被覆盖和植被环境越好。从行政区划角度看,东部区域植被生态环境最好,其次是中部区域、西部区域,主城区植被及生态环境较其余3个区域略显不足。植被好的区县(地区),平均海拔高度值偏大。(3)三峡大坝完成175 m蓄水后较蓄水前(2000-2003年阶段),远离河道区域,植被指数在春、秋、冬季节呈现增加趋势,夏季植被指数呈减小趋势;近河道区域,植被指数在春季降低、秋季增加,夏、冬季有增有减。由于夏季全河道处于雨季,降雨偏多,河道会长期处于洪峰或高水位过程,河道被淹没的区域扩大;加之三峡蓄水后,夏秋季节河道上空薄云、碎云等云雾增加,即使夏半年三峡库区处于放水阶段,夏秋季节植被指数仍略有减小的趋势。冬半年河道基本不会出现高水位,河道内裸露土增加,适于植被生长。冬半年虽然处于蓄水阶段,但植被指数仍有增加趋势。

To analyze the vegetation and vegetation variation along the Yangtze River(Chongqing section), 16 days normalized vegetation index product of MODIS level 3 MOD13 A1 from 2000 to 2015 was used to analyze the temporal and spatial distribution characteristics and changing trend of vegetation index of 22 districts and counties along the Yangtze River in Chongqing. The results were shown as following.(1) After the impoundment of the Three Gorges Reservoir, the ecological vegetation and the vegetation environment along the Yangtze River showed a good trend, and were improved obviously, especially in the eastern area of the Yangtze River.(2) The vegetation cover and the vegetation environment were better farther away from the river.From administrative divisions, the ecological environment of vegetation in the eastern region was the best,followed by the central region, then the western region and the main urban. And the area(region) whose vegetation was better had higher mean altitude.(3) After the impoundment of 175 m, the vegetation index in the Yangtze River and 250 m area away from the river was obviously lower than that before the impoundment(2000-2003) in spring. Far from the Yangtze River, the vegetation index showed an increasing trend in spring,autumn and winter, and a decrease in summer, while near the Yangtze River, the vegetation index decreased in spring, and increased in autumn and had either increase or decrease in summer and winter. In summer, the whole river channel is in the rainy season and the rainfall will be more, the river will be in flood peak or with high water level that the flooded area of the river will be enlarged. After the Three Gorges water storage, thin clouds and broken clouds increased, leading to the vegetation index decrease even in the discharging stage during the summer half year. In the winter half year, there was no high water level in the river, and the bare soil in the river increased, which was suitable for vegetation growth. Although in the water storage stage, the vegetation index still had an increasing trend.