Geometrical considerations for evaluation of reserve design

Abstract

The edge effect, generated by the interaction of patch and matrix is preferably described by the interior-to-edge ratio of the patch. This ratio quantities the extent of microclimatic changes at the boundary, and influences nature reserve deign. As shown for elliptical and rectangular shapes, large and isodiametric patch designs are characterized by high interior-to-edge ratios. Different patch geometries can however lead to similar values of the ratio. A reference value, based upon the patch size, is therefore proposed to normalize the ratio to its maximum value, as observed for a perfectly isodiametric patch. The effect to patch geometry on the normalized ratio is discussed, as well as patch ranking based upon both the simple ratio and normalized interior-to-edge ratio. An example is included using forest patches in the Belgian Campine region to illustrate the usefulness of the proposed index.