see also: Fraver, S. 1994. Vegetation responses along edge-to-interior gradients in the mixed hardwood forests of the Roanoke River basin, North Carolina. Conservation Biology 8(3):822-832.
When compared to forest interiors, forest edges typically have an altered plant species composition and community structure, a phenomenon known as "edge effect." Edge effects make the functional interior of a forest smaller than its actual area. The objective of this study was to estimate how far the effects of agriculturally maintained edges penetrate the mixed hardwood forests of the Roanoke River Basin, North Carolina. I determined percent cover for all vascular plant species in 10 x 100 m belt transects on north-facing or south-facing edges of four relatively undisturbed forests. Changes in the percent cover of individual species, the relative cover of exotic species, and species richness indicated that edge effects penetrate deeper on south-facing edges (to 60 m) than on north-facing edges (to 20 m). Mid-day air temperatures were higher and relative humidities were lower near the edge than in the interior, with temperatures stabilizing at 20 m inside the forest and relative humidities at 10 m for both north and south orientations. Analyses of species responses to the edges showed a number of species to be edge oriented; however, no species were found to be interior oriented. The results of multivariate analyses (ordination and cluster analysis) suggested that edge effects could be detected to 50 m on south facing edges and 10-30 m on north-facing edges. These results allow us to better understand the difference between a forest's actual area and its functional interior area.
See a graphic of what all of this means
WHEN I HEARD THE LEARN'D ASTRONOMER
When I heard the learn'd astronomer,
(Walt Whitman, Leaves of Grass)