基于MODIS-NDVI汶川震中区域十年后植被恢复的时空变化特征分析

Temporal and Spatial Variation Characteristics of Vegetation Restoration Based on MODIS-NDVI Wenchuan Earthquake Region in Ten Years

为分析研究受汶川地震影响下茂县、汶川以及都江堰三县的植被动态恢复状况,通过对中分辨率成像光谱仪-植被指数(MODIS-NDVI)时间序列数据计算2007~2017年各年的植被覆盖度,进一步计算2009~2012年以及2013~2017年植被覆盖恢复率,并结合地形地貌、地质构造、地质灾害、植被类型和人类活动等影响因素探讨该地区植被恢复的时空差异变化。结果表明:研究区植被在2007~2017年这10年内随着时间逐渐恢复,且恢复较好,但震中区域差异明显;结合实地调查滑坡数据,得知研究区与滑坡区植被恢复都表现出明显的滞后性;海拔和道路距离与植被恢复面积比分别存在显著的相关性;不同坡向上的植被恢复面积比也存在差异;研究区内地质构造复杂的区域地质灾害频发,灾害密度越大,植被恢复显著点较少;由于各种植被类型的特性不同,导致植被恢复的快慢不同,其中草甸、针叶林、阔叶林及灌丛自然恢复速率较快。可见,研究区内植被恢复受到自然与人为等多种因素影响,震后绝大部分区域植被在10年内恢复到震前水平,但部分区域需要人类进行政策保护,研究结果可为地震灾后植被恢复的决策干预提供理论支撑。

In order to analyze and study the dynamic restoration of vegetation in Maoxian,Wenchuan and Dujiangyan counties under the influence of Wenchuan earthquake.They calculated the vegetation coverage of each year from 2007 to 2017 by using MODIS-NDVI time series data,further calculated the vegetation coverage recovery rate from 2009 to 2012 and 2013 to 2017,based on the influencing factors such as topography,geological structure,geological hazard,vegetation type and human activities,the temporal and spatial differences of vegetation restoration in this area were discussed.The results show that the vegetation in the study area gradually recovered over time in the past 10 years,and the recovery was better,but the epicenter area was significantly different.Combined with the field investigation of landslide data,it is known that the vegetation restoration in the study area and the landslide area has shown obvious hysteresis.There was a significant correlation between altitude and road distance and vegetation restoration area ratio;there was also a difference in vegetation restoration area ratio between different slopes;In the study area,geological disasters with complex geological structures were frequent,The more disaster density,the less significant point of vegetation restoration;Due to the different characteristics of various vegetation types,the speed of vegetation restoration was different,and the natural recovery rate of meadow,coniferous forest,broad-leaved forest and shrub was faster.It is concluded that the vegetation restoration in the study area is affected by many factors such as nature and man-made,after the earthquake,most of the vegetation can be restored to the pre-earthquake level within 10 years,but some regions need human policy protection,the results can provide theoretical support for decision-making interventions for vegetation restoration after earthquakes.