北洛河流域植被覆盖度时空变化的遥感动态分析

Spatiotemporal Variations of Vegetation Coverage in Beiluo River Watershed Based on Remote Sensing Data Analysis

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。

The spatiotemporal trend of vegetation coverage in Beiluo River watershed was analyzed to understand the eco-environmental evolution and runoff—sediment behaviors on the Loess Plateau.TM images of 1987,1995and 2007with a spatial resolution of 30m were employed,the normalized difference vegetation index（NDVI）was then calculated,and the dimidiate pixel model was used to get vegetation coverage degrees and its classification.Results showed that（1）under the double influences of climate change and human activities,the vegetation coverage in Beiluo River watershed experienced the process of slow to rapid increase from 1987to 2007.The vegetation coverage degrees for the whole watershed were 41.12%,46.43% and 63.43%in 1987,1995and 2007,respectively.（2）The vegetation coverage both in the hilly-gully and tablegully regions showed a slow to rapid trend from 1987to 2007,and the rocky-mountain region kept the relatively stable forest coverage.The intense vegetation restoration mainly occurred in Wuqi and Zhidan Counties and Luochuan tableland in the watershed.