Dynamic analysis on spatial pattern of dominant tree species of cold-temperate coniferous forest in the succession process in the Pangquangou Nature Reserve FRACTAL ANALYSIS OF THE DYNAMICS OF POPULATION PATTERNS DURING VEGETATION SUCCESSION Dynamic Analysis on Spatial Pattern of Betula platyphylla and Larix principis-rupprechtii in the Succession Process in Taiyue Mountain of Shanxi Province A new landscape expansion index: definition and quantification