汶川地震震中地区崩滑体的植被恢复与长期效应

Vegetation Recovery of Co-seismic Landslide and Long-Term Effect at Central Area of Wenchuan Earthquake

[目的]评估汶川地震震中地区崩滑体自然植被恢复过程,旨在为该区震后地质环境恢复、灾害防治和重建提供依据。[方法]以四川省汶川县映秀镇为研究区,以多期空间分辨率为30 m×30 m的Landsat遥感影像为数据源,分析震后崩滑体上的植被动态恢复变化,结合地形因子分析地震9 a后植被恢复的空间分布特征。[结果]研究区震后至2011年,经历植被恢复程度较差,差等水平以下占比68%,期间暴雨泥石流活动频率高,至2013年后就达到一个较好的恢复水平,差等水平以下占比32%,之后就处于一个缓慢的恢复过程,至2017年植被恢复差等以下的崩滑体仍主要处于30°~50°的坡度区间,1500~2100 m高程区间、东南坡向。[结论]四川省汶川县映秀镇总体上经过近9 a的恢复过程,植被覆盖度恢复到0.74,与震前相比差值为0.08,根据拟合模型预计2022年植被覆盖度能恢复到震前水平,但仍主要以草本和灌木为主,植被种群结构与震前差异较大。

[Objective]The vegetation recovery process of the co-seismic landslide at central area of Wenchuan earthquake was assessed in order to provide the basis for the ecological environment restoration,disaster prevention,and reconstruction after the earthquake in the study area.[Methods]Yingxiu Town of Wenchuan County,Sichuan Province was taken as a study area,and the dynamic changes of vegetation at landslide sites after the earthquake were analyzed based on multi-temporal images with a resolution of 30 m.The spatial distribution characteristics of vegetation recovery in the past nine years were analyzed based on the topographic factors.[Results]The vegetation of the landslides did not recover well from 2008 to 2011 in the study area,and 68%of the sites were below the“poor”level.During this period,the frequencies of rainstorms and debris flow activity remained high.After 2013,a better recovery level was reached overall,and the number of landsides below the poor level decreased to 32%.Then,it had been in a slow recovery process.In 2017,the landslides with a poor level of vegetation recovery were mainly located in the slope range of 30°—50°,the elevation range of 1500—2100 m,and a southeast slope aspect.[Conclusion]In the 9 years after the earthquake,the vegetation cover index increased to 0.74,and the average vegetation coverage index value was 0.08 less than that before the earthquake.Based on the statistical model,the vegetation cover index is expected to return to the pre-earthquake level in 2022.However,the population structure of vegetation with herbs and shrubs is different from that before the earthquake.