Fractal characteristics and stability of spatial structure of forest landscape along the Ming Great Wall in Beijing

In order to have an overall understanding of the fractal characteristics and stability of spatial structure of forest landscape along the Ming Great Wall in Beijing, fractal theory was applied in this paper. The census data and recent forest resource survey data for the Beijing Great Wall were used as the main data source, and the buffer width area of 3 000 m on both sides of the Ming Great Wall as the study object. Based on the statistics data of patch perimeter and area of each landscape type, and the quantitative analysis of the relationships between scale and frequency of patch shape index as well as perimeter and area of each landscape type, the fractal characteristics and stability of each landscape type were analyzed combining with the fractal dimension and stability index. The results showed that the relationships between scale and frequency of patch shape index as well as perimeter and area for each landscape type in the study area objectively exist. The statistics of perimeter and area showed that the study area was dominated by forest land and shrub land, and the sum proportion of two up to 83.38%, while the area proportion of open forest land and forest clearings was less, respectively 0.76% and 0.36%. The analysis of mean patch shape index, fractal dimension and stability index showed that agricultural land and other landscape types had the most irregular patch shapes, the highest degree of complexity, the greatest degree of space occupied, and the lowest stability, while the open forest land had the most regular patch shape and the highest stability. The landscape stability index of agricultural land was -0.087, indicating stability with complex morphology. On the whole, the natural landscape, when compared to the landscape used by humans, had more regular patch shapes and greater stability. Topography and human disturbance are the major impact factors.