基于Landsat TM数据的潮白河流域植被覆盖变化研究

A Study on the Vegetation Cover Change in Chaobaihe Riverbasin Based on Landsat TM Images

使用经严格配准的同一时间(1991年和2002年)LandsatTM图像数据,编制归一化植被指数(NDVI)图,进而计算生成植被覆盖度图像。通过掩膜技术和变化检测等提取了北京潮白河流域中上游地区从1991～2002年的植被覆盖变化信息。研究结果表明,北京潮白河流域中上游地区11年间植被退化的总面积为1635.3km2,占该区域总面积的30.6%;其中植被覆盖度为40%～50%的类型退化的面积最多,为411.74km2,变化率为66.0%,覆盖度为90%～100%的类型退化的面积最少,为14km2,变化率为4.4%;覆盖度为30-40%的类型变化率最大,为100%,覆盖度为90%～100%的类型的变化率最小,为4.4%;从植被覆盖度变化的趋势来看,随着植被覆盖度的增加,变化率在逐渐降低;流域中游、密云水库北部和东北部以及上游的河谷地带由于受人类活动干扰的强度较大,植被退化较严重;而上游的山地区域由于人类活动干扰较少,再加上近年来采取封山育林、植树造林等措施,植被覆盖程度有所改善。

Abstract: Normalized difference vegetation index(NDVI) maps are plotted from accurate registrated images of Landsat TM in the same periods in 1991 and 2002 and vegetation coverage maps are computed and drew from them. The vegetation cover change for the Chaobaihe riverbasin of Beijing from 1991 to 2002 is derived using mask and change detection technologies. The results of research show that the total area of vegetation degradation of Chaobaihe riverbasin of Beijing is 1635.3km 2 in 11 years, which consists of percentage 30.6%; The greatest degradation is the area that coverage is between 40% and 50%, its area is 411.74 km 2, change ratio is 66.0%; The smallest degradation area is the vegetation type that coverage is between 90% and 100%, its area is 14 km 2, change ratio is 4.4%; The vegetation that coverage is between 30% and 40% has the greatest of all vegetation types and is 100%. The vegetation that coverage is between 90% and 100% has the smallest change and is 4.4%; The change ratio reduces gradually as the vegetation coverage increases; Owing to human activity, the intense vegetation degradation regions are the middle reaches of the riverbasin, the northern and northeastern part of Miyun reservoir and the river-valley part of upper reaches; The vegetation cover in the mountainous regions of the upper reaches have been improved as a result of close hillsides to facilitate afforestation and afforestation campaign.