汶川地震灾区植被覆盖度变化与地形因子的关系

Vegetation Variations and Correlations with Topographic Factors in Wenchuan Earthquake Area

[目的]分析植被覆盖度变化与高程、坡度、坡向3种地形因子关系,为汶川地震灾区环境监测及修复、水土保持、灾害评估与防治等工作提供一定依据。[方法]通过构建汶川地震灾区像元二分模型估算植被覆盖度,分析植被覆盖度与地形因子之间的关系。[结果]高程小于3 000m的各高程带、各坡度带中平均植被覆盖度、高植被覆盖度减少,低植被覆盖度增加的比例均与高程、坡度呈负相关。高程低于500m,500~1 000m区域和坡度小于5°的区域其植被受地震影响大,恢复周期更长,截至2015年5月,尚未达到震前水平。各坡向区平均植被覆盖度,高、中、低植被覆盖度比例变化趋势较为一致,无明显差异,东、南、东南、北方向各等级植被覆盖度比例已达到震前水平。[结论]植被覆盖度与地形因子之间关系密切,植被覆盖的动态监测可以从地形变化出发。

[Objective]To investigate the relationship between the vegetation coverage change and topographic factors（elevation,slope and slope aspects）in order to provide basics for environmental monitoring and restoration,soil and water conservation,and disaster assessment and prevention in Wenchuan earthquake area.[Methods]By using dimidiate pixel model to estimate vegetation fraction in the earthquake area,the relationships between vegetation fraction and topographic factors was analyzed.[Results]Vegetation fraction had negative correlations with slope and elevation（〈3 000 m）.Similar negative correlations were also found between the topographic factors and the proportion of low vegetation coverage.The effect of earthquake on the vegetation was dramatic in the area with elevation〈500 m,and area with elevation ranged from 500 to 1 000 m and slope〈5°,where the recovery period was longer.Until May 2015,vegetation recovery has not reached to the level before the earthquake.Besides,there were no significant differences between variation of vegetation coverage and proportion change of high,middle and low vegetation coverage area among different slope aspects.The proportion of high,middle and low vegetation coverage area in the east,south,north and southeast had been restored to the levels before the earthquake.[Conclusion]Vegetation fraction is closely related to topographic factors,and dynamic monitoring of vegetation status can be obtained from topographic changes.