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采用1987,1995及2007年3期Landsat TM遥感影像,计算归一化植被指数(NDVI),利用像元二分法估算植被覆盖度并进行分级,分析了北洛河流域近20a的植被覆盖变化趋势,对黄土高原地区环境演变及水沙变化机理分析提供基础数据信息。研究结果表明:(1)在气候变化和人类活动双重影响下,1987—2007年北洛河流域植被呈缓慢增长—迅速增长趋势,其流域植被覆盖面积比例从41.12%,46.43%,增加至63.43%。(2)流域不同分区中,丘陵沟壑区、高塬沟壑区植被均呈缓慢增加—迅速增加的趋势,而土石山林区植被表现出较强稳定性。丘陵沟壑区植被恢复以吴旗、志丹县为主,高塬沟壑区植被恢复以洛川塬为主。
Landsat TM remote sensing images of 1987, 1995 and 2007 were used to calculate normalized vegetation index (NDVI). Vegetation coverage was estimated and classified by pixel dichotomy. The trend of vegetation cover in the recent 20 years in the Beiluohe River Basin was analyzed , Provide basic data information on the environmental evolution and the mechanism of water and sediment change in the Loess Plateau. The results show that: (1) Under the dual influence of climate change and human activities, the vegetation in the Beiluohe River Basin increased slowly from 1987 to 2007, increasing rapidly, and the proportion of its vegetation coverage area increased from 41.12% and 46.43% to 63.43 %. (2) Vegetation in the hilly and gully areas and high-upgrowth gully areas showed a slow increase-rapid increase in different sub-regions of the basin, while the vegetation in the mountainous areas of the Shushishan showed a strong stability. Vegetation recovery in hilly and gully areas is dominated by Wuqi and Zhidan, and the vegetation in highland and gully area is dominated by Luochuanyuan.