汶川大地震灾害对区域生态系统的影响——以青川、平武和茂县为例

Impacts of Wenchuan Earthquake disasters on ecosystem and its spatial pattern:case study of Qingchuan,Pingwu and Maoxian counties

利用Landsat-TM/CBERS遥感数据和1∶25万高程数据,分析汶川特大地震灾害前、后土地利用/土地覆被变化。为了研究地震对区域生态系统的影响,定量对比分析了重灾区青川、平武和茂县主要土地利用/土地覆被的特征,计算不同坡度和坡向影响下土地利用/土地覆被类型变化。得出以下结果:(1)地震后造成区域内有林地、草地和耕地面积减少;疏林地面积增加。有林地、草地和耕地分别减少了92.09、46.98km2和30.81km2;疏林地增加了98.81km2。(2)研究区自然和耕地生态系统受地震影响明显。通过对3县自然和农田生态系统分析,青川林地、草地和耕地生态影响最严重;平武和茂县也存在不同程度影响。(3)在不同的坡度下,土地利用/土地覆被类型在>35°坡度段受地震影响面积变化最大,依次是0～8°、15～25°、8～15°和25～35°坡段。这与震后诱发的崩塌、滑坡、水土流失等次生灾害,促使大量覆被携带山体、岩石整体或局部的、不规则的运动有关。在不同坡向下,土地利用/土地覆被类型在半阴坡坡向受地震影响面积变化最大,其次是半阳坡、阴坡和阳坡;这与区域内不同坡向上的土地利用/土地覆被类型优势度相关。

Based on two periods of land cover maps derived from remotely sensed date, Landsat TM, CBERS and digital elevation model （DEM） derived from 1：250 000 topographic maps. Studies on land use/land cover changes （LUCC） of Qingchuan county, Pingwu County and Maoxian county before and after Wenchuan Earthquake, and the influences of two importance cause of slope and aspect in ecosystem. The main results are as follow ： after earthquake, the area of woodland, grassland and farmland decreased obviously by 92.09km2,46.98 km2 and 30. 81 km2 respectively, open forest land increased by 98.81 km2 for area. The open forest land area changes amplitude is most, the value is 6.20%. Results indicated the ecosystem is degenerating and in study regions after earthquake, especially Qingchuan county. Topographic conditions are of great importance to the distribution of land use/land cover and the process of land cover changes. Under different slopes, there are large area changes of LUCC great than 35° because of earthquake. The order are 0 --8°, 15 --25°, 8 -- 15° and 25 -- 35°. These changes have obviously relation with earthquake and the secondary mountain disasters such as rock fall, landside, and debris flow. Aspect has a large influence on the distribution of land cover types, especially in half-shady slope ; the order is half-sunny slope, shady slope and sunny slope. The area changes amplitude of land cover types are obviously in different aspect.