Vegetation Structure and Environmental Conditions of Forest Edges in Panama

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Abstract
Micro-environmental conditions, vegetation structure and tree mortality in five forest edges ten months to twelve years old were studied in the tropical premontane wet forest of Panama. Along transects from clearings to the interior of the forest, the greatest change in temperature and relative humidty occurred between 2.5 and 1.5 m into the forest. The forest canopy was most open at the clearing-forest border. At the most recently cleared site, this open canopy extended farther into the forest edge than at sites where clearing took place earlier. Density and basal area of trees (< 10 cm diameter at 1.3 m high) were twice as great at the forest edges compared with the interior of forests at the sites where the boundaries were created five to twelve-years previously. Floristic composition was unchanged along transects from the forest boundaries to the interior of forests and light-demanding species were not more abundant in forest edges compared with the forest interior. The edge:interior ratio of trees that died after the edges were created was 14:1. Beyond 15-25 m into the forest, neither environmental conditions nor the forest structure and and tree mortality were influenced by proximity to the forest boundary. Between 0 and 15 m, however, vegetation structure changed with both distance from the forest boundary and time elapsed since clearing. This study indicates the ecological significance of edge vegetation as a buffer protecting forest vegetation from conditions in adjacent clearings.