Landscape change and its spatial heterogeneity in Yellow River Delta based on boundary characteristics

Taking Yellow River Delta as study area,the landscape element information of August 24,1992 and August 9,2001 were extracted by supervised classification,and the boundary characteristics of various elements were acquired by using 2×2-pixel boxes skimming over the landscape map.The landscape indices such as diversity,evenness,heterogeneity,and spatial complexity were calculated based on boundary number and cumulative length,and,considering of the spatial distribution and gradient change of various landscape elements,the landscape components heterogeneity of farmland and Tamarix chinensis-Phragmites communis were analyzed by using information entropy and lacunarity index methods.The results indicated that in study period,the boundary characteristics were more complicated,reflecting the transformation from farmland to T.chinensis-P.communis as a result of town expansion,oil exploitation,and water break off in the Yellow River.Compared with those based on element area proportions,the landscape indices based on boundary characteristics could give more detailed information on landscape structure.In 1992-2001,the spatial distribution of farmland and T.chinensis-P.communis in study area showed macroscopic heterogeneity,while partly microscopic heterogeneity at smaller scales.The heterogeneity scale of T.chinensis-P.communis was 50-pixel smaller than that of farmland,and the scale gap between them enlarged with time.Information entropy and lacunarity index methods,especially used together,could well indicate the landscape heterogeneity.