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

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