A diffusion model for dispersal of Opuntia imbricata (cholla) on rangeland

Overgrazing creates gaps or open spaces for cholla seeds or stems that fall to the ground to become established (passive dispersal). Also livestock or wildlife may cause stems and fruits to fall to the ground (active dispersal). A theoretical model is formulated for the dispersal of plants based on the diffusion equation which assumes one or more mechanisms of dispersal. Passive dispersal alone cannot account for the current spread of cholla on some of the pastures. -from Authors