The diversity of forest stands may be affected by landscape fragmentation during periods of climatic change. A modified version of the Image model of the dynamic processes of establishment, growth, and death of forest trees is used in a spatially explicit framework to elucidate differences in the effects of both spatial structure and spatial processes. In cases with and without climatic change, the effects of including random or structured fragmentation and successively lower dispersal probabilities (increased chance of long-distance dispersal) are examined in simulation experiments. The exclusion of very low dispersal probability (p < 0.001) has an important effect on species richness. Barriers and random fragmentation also lower [...]