基于Landsat多光谱与PALSAR/PALSAR-2数据的汉江流域森林覆盖变化研究

Forest Cover Monitoring and Its Changes in Hanjiang River Basin Based on Landsat Multispectral and PALSAR/PALSAR-2 Data

汉江流域是南水北调中线工程的水源地,森林覆盖对于保障水源地生态安全具有重要作用。为监测汉江流域2007~2017年森林变化情况,以Landsat多光谱数据与ALOS(Advanced Land Observation Satellite)雷达遥感数据为基础,在Google Earth Engine平台上对数据进行处理分析,根据区域特点,选取9个特征指数,利用随机森林分类算法,提取2007和2017年森林分布,监测汉江流域森林覆盖变化。结果表明:结合Landsat多光谱数据与ALOS雷达遥感数据的分类精度最高,2007年森林分类整体精度为98.0%,2017年森林分类整体精度为98.6%,精度明显高于单独使用Landsat多光谱数据或ALOS雷达数据的森林分类结果;2007~2017年十年间汉江流域森林面积增加了5653.21 km2;森林呈现增多的区域主要分布在河南省的西峡县、南召县和丹江口水库附近,而森林呈现减少的区域在荆门市、十堰市和汉中市附近区域。

Hanjiang River Basin is the water source area of the Middle Route Project of South to North Water Diversion, and forest covers play an important role for the protection of ecological security at this place. In order to monitor the forest cover change of Hanjiang River Basin during 2007-2017, Google Earth Engine platform was used to deal with the Landsat multispectral images and ALOS(Advanced Land Observation Satellite)SAR data at the whole area. According to the regional characteristics, nine characteristic indexes were selected from both of the Landsat multi-spectral and ALSO SAR images, and random forest classification method was applied to extract the forest distribution in 2007 and 2017 for monitoring changes in forest cover in the Hanjiang River Basin. The results show that the overall accuracy of forest cover classification is 98.0% at 2007 and 98.6% at 2017, which is significantly higher than that of forest classification by using only Landsat multispectral data or ALOS SAR data. The forest cover area of Hanjiang River Basin increased by 5 653.21 km2 from 2007 to 2017. For the Xixia and Nanzhao of Henan Province and Danjiangkou Reservoirs, forest covers illustrated an increasing trend, while the forest covers around Jingmen City, Shiyan City and Hanzhong City showed a decreasing trend.