Effects of spatial grain size on landscape pattern of land use in Three Gorges Reservoir Area in 30 years

This paper is purpose to measure landscape indexes traits with changes of grain sizes, and summarize differences of landscape traits in different grain sizes. In this paper, five remote sensing images of Three Gorges Reservoir Area in 1975, 1987, 1995, 2000 and 2005 were taken as data for present study. The images were interpreted into draws of landscape pattern. In the ArcView3.3 environment, the vector draws were transformed into shatter draws according to different spatial grain size. In the same time, landscape indexes were chosen and the effects between spatial grain size and landscape indexes were measured at the scale of pattern and landscape. Then the correlation differences between landscape indexes and spatial grain size were analyzed with the method of correlation analysis. The results showed that, the traits of changes of landscape patterns were proved in 30 years. The effective sensitiveness between different landscape indexes and spatial grain size was different, such as patch density (PD), effective mesh size (MESH), standardized trait index (NSLI), aggregation index (AI), and same landscape pattern in the process of measuring was taken on different change rules, such as cultivated land (slope<25°), forestry land, grassland, urban constructive land. There were some turning points in the changes of effect, especially at 400 m. At the scale of landscape, patch density and land shape index were largely impacted by the spatial grain size. The correlation between the same index and grain shows highly consistency at the scale of pattern and time. Above all, this research can reflect the change rules of landscape indexes in different spatial grain size.