基于NDVI监测5.12震后岷江河谷映秀汶川段滑坡体植被恢复

Monitoring the Vegetation Recovery at Landslides along the Minjiang River Valley after 5.12 Earthquake using NDVI:a Case Study of the Yingxiu-Wenchuan Section

汶川5.12地震造成岷江流域生态环境严重受损,评估地震后自然植被恢复过程,对生态环境恢复和重建有着重要的意义。本研究以5.12地震前后(2007、2008及2011年)空间分辨率为30 m×30 m的TM遥感影像的NDVI指标为数据源,监测了岷江上游干旱河谷(映秀—汶川段)植被在地震前后的动态变化,并结合地形因子,分析了植被受损及地震3年后植被恢复的空间分布特征。结果表明:(1)地震造成的研究区滑坡体面积约5 413.95hm2,占总面积的34.74%;(2)滑坡体发育总体上与海拔呈负相关,与坡度呈正相关,与坡向无显着相关;(3)地震3年后,受损植被的平均恢复率达66.71%,其中中等及良好恢复的面积为3 942.54 hm2,占滑坡总面积的72.82%。研究结果也显示植被恢复与坡度、海拔有很高的一致性,及植被恢复的复杂性。

The Wenchuan Earthquake （ Richter scale 8） on May 12, 2008 caused widespread ecosystem dama- ges in the Minjiang River Basin. It is important to evaluate the natural vegetation recovery process and provide basic information on ecological aspects of the recovering environment after the earthquake. To circumvent weather limits of remote sensing and to meet the need for regional observation analyses, three Landsat TM images pre- and post-earthquake in the Minjiang arid valley were used for analysis. The post-earthquake vegetation cover val- ues were compared to the pre-earthquake value to determine the extent to which the vegetation was damaged in relation to the pre-earthquake pattern, and the rate of recovery was evaluated. Spatial characteristics of vegeta- tion loss and natural recovery pattern were analyzed in relation to elevation, slope and aspect. The results showed that （ 1 ） the landslides caused by the earthquake was 5 413.95 hm2, accounted for 34.74% of the total area; （2） there is a good correlation between recovery rate and both slope and elevation; （3） after three years, the average vegetation recovery rate reached 66.71%. Our study also showed that there was a high congruency be- tween recovery rate and both Slope and elevation, and the recovery patterns were complicated.