PATTERNS AND DETERMINANTS OF EDGE VEGETATION OF A MIDWESTERN FOREST PRESERVE

To discern the effects of edge age, orientation, and adjacent vegetati on structure on forest-edge composition, I surveyed and compared woody species composition in the forest interior and in edges located along roads encircling and bisecting Hueston Woods Nature Preserve, an old- growth beech-maple forest in southwestern Ohio. Among-habitat comparis ons of species importance values and stem size-class distributions, co upled with the results of a DCA ordination, indicated compositional di fferences between: (1) edge and interior stands and (2) edges borderin g young (35 years) open edges and older (> 60 years) closed edges. Com positional changes corresponded to an assumed microclimatic gradient b ased on the structure of the adjacent vegetation. Specifically, open e dges were dominated by shade-intolerant and highly shade-intolerant sp ecies in almost ail size classes; closed edges lacked highly intoleran t species, but contained a number of shade-intolerant species (e.g. Pr unus serotina; Fraxinus americana); interior stands were composed almo st exclusively of shade-tolerant species. Size-class distributions acc ording to shade-tolerance classes highlighted the importance of edge a ge: the older edges contained a high percentage of canopy-level shade- intolerant individuals that apparently were able to exploit the higher light conditions following edge creation. Edge composition was not co rrelated with edge orientation, however, perhaps because of other conf ounding factors such as site-specific hydrologic factors and random es tablishment patterns.