Edge effects on recruitment of Trillium camschatcense in small forest fragments

To evaluate edge effects on recruitment of the understory perennial herb Trillium camschatcense, spatial distribution and stage-class structure based on four life-history stages were investigated within a small forest fragment in eastern Hokkaido, Japan. Seedlings were most affected by edge effects. The density of seedlings was considerably lower in the forest edges than in the interiors and was higher on the northern side of the forest. Although three stages suffered edge and orientation effects, flowering plants experienced much more moderate edge effects than juvenile stages and showed relatively uniform distribution. The results suggest that the recruitment of juvenile stages was strongly limited near forest edges. Seedling density was correlated with microclimatic conditions, not with seed production. The edge and orientation effects on stage-class structures were also observed in two other small populations, emphasizing the role of edge-related decreases in seed germination and subsequent survival for limiting the recruitment of small, fragmented populations of T. camschatcense. (C) 2003 Elsevier Ltd. All rights reserved.