长江中上游地区退耕还林成效监测与评价

将长江中上游地区84个地市级区域作为一个整体,利用GIS综合解译分析归一化植被指数(NDVI)、土地利用类型和数字高程模型(DEM),揭示该区域退耕还林工程所取得的成效.结果表明: 2000-2015年,研究区域NDVI持续增长;与2000年相比,2015年长江中上游地区有2.1%的耕地不再耕种,坡度>35°坡耕地的25%实现了退耕,25°~35°坡耕地的2.7%实现了退耕,中坡度耕地绝大部分实现退耕;耕地主要转变为林地和草地.研究期间,林草覆盖度增加显著,增幅达21.9%;低植被覆盖度的土地面积大幅减少,植被覆盖度小于10%的面积减少95.3%,高植被覆盖度的土地面积显著增加;土壤侵蚀强度总体降低,轻度、强度、极强度等级土壤侵蚀的土地面积均减少10%以上,但剧烈土壤侵蚀状况未得到缓解.研究区森林覆盖率达到60%,但不同时段覆盖度的变化比例存在差异,空间分布不均匀,呈现东部高、西部低的特征,需要继续加强治理.

Monitoring and evaluation of the effects of Grain for Green Project in the upper and middle reaches of China’s Yangtze River.

Based on the comprehensive interpretation of GIS, we analyzed the normalized vegetation index (NDVI), land use types and digital elevation model (DEM), and revealed the results achieved by the Grain for Green Project in 84 prefecture-level regions in the middle and upper reaches of the Yangtze River. The results showed that the NDVI was growing in this area from 2000 to 2015. Compared with 2000, 2.1% of the farmland was no longer cultivated. 25% of the farmland with slope more than 35°, and 2.7% of the farmland with the slope of 25° to 35°, and the most part of moderate slope farmland had been converted. Arable land was mainly converted to woodland and grassland. The coverage of forest and grassland significantly increased, with an enhancement of 21.9%. The land area of low vegetation coverage was greatly reduced. The area with vegetation coverage less than 10% decreased by 95.3%, while the land area of high vegetation coverage significantly increased. The soil erosion intensity generally reduced. The land area with mild, strong, extremely strong soil erosion grade were all reduced by more than 10%, whereas severe soil erosion had not been alleviated. The proportion of forest coverage was 60% in this area. The magnitude of vegetation coverage changes varied in different periods. The spatial distribution was uneven, with higher coverage in the east than in the west. More works are needed to strenthen the management of Grain for Green Project in this area.