Boundary Form Effects on Woody Colonization of Reclaimed Surface Mines

Abstract

Woody plants and evidence of browsing were measured on eight reclaimed strip mines in Maryland and West Virginia to see whether revegetation patterns differed adjacent to concave, straight, and convex forest boundaries. Two clonal species predom- inated (Rubus allegheniensis and Robinia pseudoacacia), followed in abundance by three wind-dispersed species (Fraxinus americana, Acer rubrum, Betula lenta), and a variety of animal-dispersed species. Mine transects adjacent to concave forest boundaries had 2.5 times as many colonizing stems as those next to convex boundaries. Stems of colonizing species extended > 61 m from concave boundaries, but rarely > 13 m from convex bound- aries. Stem density of all the common animal-dispersed species was correlated with their abundance in the adjacent forest edge, whereas no relationship existed for Robinia or the wind-dispersed species. Evidence of browsing was greater adjacent to concave boundaries than opposite convex boundaries. These strikingly different colonization patterns appear to be primarily the result of the immigration process interacting directly with shape as a spatial characteristic. Through time, a "concave-convex reversal" in boundary form is evident. This results from a "cove concentration effect" where the greatest boundary ex- pansion rate is in coves being colonized. Almost all patterns next to straight boundaries were intermediate between those opposite concave and convex boundaries. We conclude that boundary form may exert a powerful control over adjacent ecosystems in a landscape. This presents significant opportunities for planning and managing surface mines and other colonizing areas.