【摘要】 基于混合像元分解方法,利用Landsat TM卫星遥感数据监测了岷江上游干旱河谷区映秀\汶川段河岸带植被在汶川地震前后的植被覆盖动态变化,并结合高程、坡度及坡向数据,分析了植被受损及地震3a后植被恢复的空间分布特征。结果表明,地震造成研究区河岸带植被的受损总面积为2736.61hm2,且集中分布在海拔1100—1700m,坡度25—55°之间以及东、东南和西坡;地震3年后,受损植被与震前相比,共恢复了56.20%。更多还原

【Abstract】 Disturbances,especially large and infrequent disturbances are usually understood as events that disrupt the equilibrium state of an ecosystem by producing abrupt changes in its structural and functional characteristics that may persist for decades to centuries.Earthquake,as a typical catastrophic disturbance event,plays an important role in several ecological processes by partially or completely removing the vegetation layer.The Wenchuan Earthquake(Richter scale 8) on May 12,2008 in southwestern China caused widespread ecosystem damages in Longmenshan area.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 in the Wenchuan earthquake-hit areas 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 values 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 vegetation loss and natural recovery pattern were analyzed in relation to elevation,slope and aspect.Our study focused on the following four aspects:(1) to detect the changes in riparian vegetation cover at different stages of the Wenchuan earthquake sequence,(2) to analyze the difference/similarity in the spatial distribution and recovery trajectories of the damaged vegetation under different geomorphological conditions,(3) to understand to what extent does the vegetation cover reestablish after the earthquake and(4) to track the rate of post-earthquake vegetation recovery.Results of this study indicated that the severely damaged sites occurred mainly within the range of 1100—1700m elevation and on slopes of 25—55°.After three year of natural regeneration,56.20% of the destroyed areas were recovered.Moreover,there is a good correlation between recovery rate and both slope and elevation,and the recovery patterns are complicated in the damaged area.Our study showed that there was a high congruency between recovery rate and both slope and elevation,and the recovery patterns were complicated.Our analyses provided very useful information for decision-making and policy-planning in the arid valley of Minjiang River after the Wenchuan earthquake.Although the natural recovery for the vegetation is a slow process,most of the earthquake-induced damages can be restored to their original condition through natural succession.Thus,human assistance or disturbance may not be a good way to treat most of the damaged areas of natural vegetation regrowth capability.To assist the natural succession or original vegetation recovery,human interference and ecotechnology measures should only be introduced to areas where vegetation regrowth is difficult,such as the areas with unstable surfaces.更多还原