汶川地震前后茂县植被覆盖度变化研究

Vegetation Coverage Change of Maoxian County Before and After Wenchuan Earthquake

"5.12"汶川地震引起的滑坡、泥石流、崩塌等次生地质灾害对灾区的植被覆盖造成严重的破坏。茂县地处于地震重灾区,查清地震对茂县植被覆盖的破坏程度可为植被修复提供参考依据,便于防控水土流失和地质灾害隐患。选取茂县地震前后Landsat 5TM的遥感影像作为数据源,采用归一化植被指数和像元二分法为估算模型,提取地震前后茂县植被覆盖度数值。通过对数据的研究将该区植被覆盖度划分为4级:高植被覆盖区、中植被覆盖区、低植被覆盖区和无植被覆盖区,并对每种覆盖类型的变化进行统计分析。结果表明,地震对高植被覆盖区的影响最严重,中植被覆盖区的影响次之,低植被覆盖区的影响最小;植被覆盖度破坏较严重的区域主要分布在坡度大于40°的地区。

Landslides,mudslides,avalanches and other secondary geological disasters,triggered by＂5.12＂ Wenchuan earthquake,have severely damaged vegetation in the region.Maoxian County is one of the earthquake disaster areas.Identifying changes of Maoxian County′s vegetation coverage can provide a reference for vegetation restoration and is helpful to control soil erosion and geological disasters.Landsat-5TM remote sensing images for Maoxian County before and after the earthquake are selected as a data source and the normalized difference vegetation index and dimidiate pixel estimation model are used to analyze the vegetation coverage changes.Through the study of the data,the vegetation coverage is divided into high vegetation coverage,moderate vegetation coverage,low vegetation coverage and no vegetation coverage areas.Statistical analysis is made for the coverage change in each area.Results show that the earthquake has severely affected Maoxian County′s vegetation coverage,with the high vegetation coverage area being most seriously affected and the low vegetation coverage area being least affected.The more seriously damaged area is mainly distributed in the slope of more than 40°.