Study On Gradient Changes Of Landscape Pattern In Urban-rural Ecotone

The paper establishes a ecological transect ,with a length of 90 km and width of 16 km, utilizing the part of Tm data on 16th August 1998, from Harbin to the natural secondary forests in Maoershan, Heilongjiang Province.with supervised classification, the TM data which had been corrected and enhanced via ERDAS , combining the data of GPS in the field, was classified by seven types including: residential area, glebe, paddy field. river. shrub. broad-leaved forests. coniferous forests, at the same time, the transect was divided 5 gradient (18 km/per) using ESRI's Arcview 3.2. To capture some of the synoptic features of the landscape, several landscape pattern metrics (i.e. landscape diversity index, landscape density index, and congregation index et al) was calculated using the raster version of FRAGSTATS. The result showed that landscape diversity index and evenness index increase along the gradient, whilst dominant index decrease along the gradient zones.in general, landscape elements present concentrative distributing patterns for great size, with landscape patch density and edged density smaller and landscape heterogeneity lower than others within closing to gradient of the city. The higher landscape heterogeneity, the closer to nature secondary forest.along the gradient, landscape congregation index exhibits descendent tendency, showing a significant relationship between the extent of patch mosaic and the extent of disturbance, according to changes of landscape mean shape index(LMSI)and landscape mean Fractal dimension index, integrated disturbance(nature disturbance, human activities, vegetational inner succession or population dynamics) tend to enhance. The proportions of large, middle and small patches were small patch>middle patch>large patch in all gradient zones.from suburbs to secondary forests, the area ratio of middle and small patches was increased, but that of large patches was significantly decreased. According to the changes of landscape index with grain and extent, the finer the grain is, the larger the landscape heterogeneity in the same spatial scope and the changes of landscape heterogeneity with the extent when gram is fixed. Therefore, the research of landscape pattern is performed in a specific spatial scale.