都市域孤立林における偏向遷移

概要

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Communities and populations of forest plants in urban areas may be modified by human activities. The vegetation at 50 study sites in fragmented urban forests in Kamakura, Japan, was studied in 1988 and 1998. Changes in the plant community during a decade were analyzed by principal component analysis. In normal succession, vegetation usually shifts from deciduous forest to evergreen forest. However, the forest communities did not show such a shift to evergreen forest. Therefore, normal succession was not dominant in these fragmented urban forests. Some evergreen plants, pioneer trees, and forest-edge plants significantly increased in frequency during the ten-year period. No significant decrease of forest plants was observed. This change in species composition was related to the distance of the study site from the nearest road, residential area and forest edge, and to the number of zoochoric species. Invasion of zoochoric species from roads, residential areas and forest edges may have an important influence on community change. Such an edge effect on population levels should be considered in community conservation planning, in addition to the physiological edge effect caused by sunlight and wind. The effect of roads decreased with distance inside the forest.
2004-12-25