震区植被覆盖度动态变化及其受损研究——以芦山县为例

A Study of Dynamic Variations for Vegetation Cover and the Damage of Vegetation in the Area of the Earthquake——Taking Lushan County for Example

本文探讨了利用Landsat TM和ETM影像数据建立植被受损模型,评价了植被受损的程度,运用植被覆盖度估算的像元二分模型,估算了植被覆盖度,总体上评价了芦山县经过4·20地震前后的植被覆盖度的变化情况,同时分析了其空间分布特征。研究结果显示：①2009年至2013年芦山县平均覆盖度从75.47%降低到70.22%②两个时期植被都是以较高覆盖度为主,约占总面积的36%,其中2009年高覆盖度植被面积大量的减少,减少的高覆盖度植被主要转化成了2013年中覆盖度的植被③2009年-2013年以轻度减少和稳定为主,轻度减少区和稳定区占总面积的75.66%,剧烈减少区和减少区占总面积的9.68%。这说明2009年-2013年植被有较严重的退化趋势④植被覆盖度变化存在着空间格局差异,随高程、坡度、坡向的分布特征差异显著⑤通过植被指数构建的植被受损模型评价了地震造成的植被受损情况,其中重度受损的植被大多是滑坡、崩塌的区域。通过研究植被受损的等级和覆盖度的动态变化情况,揭示了地震灾害对地表植被的破坏状况,为灾区的生态恢复提供决策依据。

In this paper,based on Landsat TM and ETM image data,the model of damage of vegetation is established to evaluate the level of the vegetation damage,and the improved model of dimidiate pixel method is used to estimate the Fraction Cover（FC） of the study area. A description is given of the changes of FC and analysis is made of characteristics of its spatial distribution. The results have shown that：①from year 2009 to 2013,the average FC of LuShan reduced from 75. 47% to 75. 47% ②Vegetation of higher coverage had the largest area in the two periods,accounting for about 36% of the total area. A substantial reduction of area of highest rank of FC occurred in 2009,which mainly changed into middle FC in 2013. ③The area of mild decrease and stable area were dominant in the change of FC from 2009 to2013,which accounted for 75. 66% of the total area and the area of obvious reduction accounted for9. 68%. ④FC changed along with the elevation,slope and aspect. ⑤ The model of vegetation damage was established on basis of NDVI to estimate the vegetation damaged by the earthquake. Most of the severely damaged area was due to the landslide and collapse caused by the earthquake. By studying the damage of vegetation and dynamic variations for Vegetation Fraction Cover,the destruction of the vegetation by the earthquake disaster was revealed in order to provide better decision-making for the ecologicalrestoration.