锡林河流域上游河谷湿地景观格局演变及其驱动力

Driving force analysis and landscape pattern evolution in the up stream valley of Xilin River Basin

为全面揭示锡林河流域上游河谷湿地格局变化过程及驱动因素,选取1989-2015年12景Landsat卫星影像为数据源,采用质心迁移模型和景观指数方法,研究了区域湿地景观的组成及演变趋势,并探讨了湿地景观变化的主要驱动因子。结果表明:①1989-2015年,锡林河上游湿地面积整体呈减小趋势,变化率为-1. 21 km^2·a^-1;湿地面积占比在2. 55%~3. 75%。湿地质心整体向西北方向迁移,斑块面积在南北方向呈缩小趋势,而在东西方向呈延长趋势。②类型水平上,1995-2006年流域湿地斑块数量变化剧烈,1989-2000年斑块数量增加,表明景观破碎度增大,2011-2015年斑块数量呈下降趋势,景观斑块向规则化和集中化趋势发展;景观水平上,湿地最大斑块所占比例减少,斑块趋于复杂化,景观破碎度增大,香农多样性、香农均匀度指数整体呈减少趋势,湿地景观分布向均衡方向发展。③湿地面积对人口数量和牲畜量响应较为敏感,过度放牧是导致该区域湿地不断萎缩、景观多样性改变的关键驱动力。

In order to evaluate the evolution and driving factors of wetland patterns in the upstream valley of the Xilin River Basin,12 Landsat images from 1989 to 2015 were analyzed. The landscape composition and evolution trend of regional wetland landscapes were studied by the centroid shifting method and landscape index,and the major driving factors of regional wetland changes were also determined. The results allow the following conclusions to be made. (1) The area of the wetland in the upstream of the Xilin River decreased during 1989-2015 at a rate of-1. 21 km^2·a^-1. The proportion of wetland area ranged from 2. 55% to 3. 75%. The wet centroid migrated to the northwest,and the plaque area showed a narrowing trend in the south-north,while prolonging in the east-west direction. (2) At the class level,the number of wetland patches in the basin changed drastically during 1995-2006. The number of patches increased from 1989 to 2000,indicating an increase in landscape fragmentation,before showing a downtrend in 2011-2015,such that landscape patches developed toward regularization and centralization. At the landscape level,the percentage of the largest plaque in the wetland decreased,and the shape of patches tended to be complex,leading to increased landscape fragmentation. The SHDI and SHEI showed an overall decreasing trend,and the distribution of wetland landscape developed toward equilibrium. (3) The wetland area is sensitive to population and the number of livestock. Overgrazing is the key driving force in the shrinking of wetlands and changes in landscape diversity.