Wind dispersal of seeds from a forest into a clearing

Although there are many studies of wind dispersal of seeds from a forest into an adjacent clearing, no physical model has yet been advanced. The model constructed here calculates the trajectories of seeds from individual trees in the area source to a line of seed traps (in the clearing) oriented perpendicular to the forest edge. The model uses a log-normal distribution of horizontal wind velocities at a nearby reference station to evaluate wind velocities at any point in the forest and clearing as a function of both height above the ground and distance from the forest edge. The model predicts that (1) the slope of the area source dispersal curve (seed density vs. leeward distance) approximates a negative exponential; and (2) the great majority of seed deposition in the clearing is contributed by source trees lying within a few tree heights of the forest edge. An evaluation of previously published empirical data shows that the area source model adequately characterizes the decline in seed density with leeward distance.