Composition and diversity of tropical forest vegetation at Sibolangit tourism park, North Sumatra, Indonesia

Abstract Vegetation is an important component of preventing erosion and drought, regulating water hydrology, improving soil physical, chemical, biological properties, balancing the carbon dioxide oxygen in air, conserving biodiversity, effecting other biota ecosystem, supporting ecotourism potential. The effect varies depending on structure composition plants that comprise area's vegetation formation. Sibolangit tourism park, with area 24.85 Ha, was established 1980 by Minister Agriculture Decree No. 636/Kpts/Um/1980. This study aims to examine importance value index diversity species park area. data sampled using a simple random sampling method 5% intensity. observation plots were randomly placed cover all sites. Species, diameter, height, number each individual recorded during field observation. total 67 Tourism Park. dominant at tree stage Pterocarpus indicus IVI 28%. Mitrephora obtusa pole sapling stages 52% 35%, respectively. At seedling stage, Strombosia ceylanica 62%. site moderate range 2.71 Shannon-Wiener index.