石羊河下游民勤土地利用及景观格局动态分析

基于遥感（RS）和地理信息系统（GIS）平台，以石羊河下游民勤县1991和2011年遥感影像为基础数据源，分析了研究区20 a来各土地利用景观类型的变化特征，并从水土保持角度出发，利用斑块数量（NP）、斑块密度（PD）、最大斑块所占景观面积的比例（LPI）、平均斑块面积（MPS）、香农多样性指数（SHDI）、香农均匀度指数（SHEI）及分离度（F_i）7种景观指数对沙漠、重盐碱地、植被和轻盐碱地的斑块变化进行分析评价。结果表明:（1）该区域以沙漠化景观为主，且20 a来盐碱地和植被均有所减少，沙漠化扩张；（2）1991—2011年期间，区域整体景观格局的景观破碎化程度减小，景观的异质化程度呈下降趋势，表明该区整体景观格局将有利于向水土保持方向发展。（3）各土地利用类型的景观格局动态分析都显示植被破碎化程度加剧，人类活动对区域植被的干扰程度较大。

Analysis on Dynamic Characteristics of Landscape Patterns in Minqin of Shiyang River Downstream

The spatiotemporal changes of land use and cover of Minqin county in the lower reaches of Shiyang River during 1991 and 2001 were analyzed quantitatively by taking Landsat TM images as data sources and based on GIS and RS. At the same time, NP， PD，LPI ，MPS，SHDI, SHEI and Fi were used to analyze and evaluate the patch changes of desert，heavy saline soil，vegetation and saline-alkali soil. Analyses indicated that :(1) desertification landscapes counted for the largest proportion in the region, the proportion of saline-alkali soil and vegetation reduced in recent 20 years, while desertification expanded; (2) the overall regional landscape pattern and landscape fragmentation decreased and the degree of landscape heterogeneity decreased during 1991—2011, which indicated that the overall landscape pattern would be conducive to soil and water conservation; (3) various types of pattern analysis on landscape elements showed that levels of fragmentation of vegetation had been increasing, indicating that impacts of human activities on regional vegetation degree of interference were great.