基于Landsat影像的宁夏盐池县植被景观格局变化特征

Characteristic changes of landscape pattern in Yanchi,Ningxia based on Landsat image

【目的】分析宁夏盐池县植被景观格局时空演变特征,并探讨植被与降水的相关性,为该地区生态环境恢复提供理论依据。【方法】基于景观生态学原理,利用1989-2014年(25年)4期Landsat TM/OLI遥感数据,在ArcGIS和Fragstats的支持下,对盐池县植被景观格局的变化进行分析。【结果】1989-2014年,研究区植被平均覆盖度总体较低,呈增加-减小-增加的特征,植被表现为恢复-退化-恢复的反复过程,总体处于恢复趋势,且呈现出东部植被覆盖度较高、西部植被覆盖度较低的特点。景观水平上植被斑块破碎化程度明显降低,形状趋于规则化,斑块的延展性增强、连通性提升、蔓延度增大、异质性增强,各组分要素所占比例趋于不均匀化;类型水平上各类植被景观的斑块数量和斑块密度整体呈下降趋势,表明各类景观的破碎化程度整体减轻。植被斑块重心变迁主要在西北-东南方向上,植被斑块在西北方向出现退化,而在东南、东北方向出现扩张。【结论】盐池县植被景观格局的变化是植被恢复治理措施与降水共同作用的结果,其中降水是影响盐池县植被覆盖度变化、景观格局改变以及斑块重心迁移的重要因素。

【Objective】The study analyzed the spatial-temporal evolution characteristics of regional vegetation landscape pattern and discussed the correlation of vegetation and precipitation to provide basis for eco-environmental restoration in Yanchi,Ningxia.【Method】Based on the principle of landscape ecology,Landsat TM/OLI remote sensing data at 4 periods in 25 years（1989-2014）were used and the characteristics of vegetation landscape pattern were analyzed with the support of ArcGIS and Fragstats.【Result】The average vegetation coverage was generally low and presented the characteristics of increasedecrease-increase.Correspondingly,the vegetation appeared the repetitive process of restoration-degeneration-restoration with the whole tendency of recovery.The vegetation coverage was higher in the eastand lower in the west.At pattern level,landscape fragmentation degree of vegetation patch reduced obviously,the patch shape tended to have increased connectivity,enhanced contagion,reduced diversity,increased heterogeneity and different component ratios.At class level,the patch number and patch density of vegetation landscape declined,indicating that landscape fragmentation degree was reduced.During 1989-2014,gravity center of vegetation patch moved mainly on the direction of NW-SE,and vegetation patches expanded in the southwest and northeast of the study area,but degraded in the northwest.【Conclusion】The change of vegetation landscape pattern was the consequence of vegetation restoration measures and precipitation,and precipitation was an important factor of vegetation coverage change,landscape pattern variations and vegetation patches migration.