Spatial Distribution Pattern and Interspecific Association of Main Tree Species in Pinus tabulaeformis Forest in Ziwuling Mountains Spatial-temporal variability of land use with terrain gradient in Taihang Mountain, Hebei Province Spatial distribution index and its applicability evaluation for single-type landscape Gradient analysis on the influence of terrain on the forest landscape pattern in the burned blanks of the north slope of Mt. Daxing‘anling