Struktur dan Komposisi Vegetasi Pohon Berdasarkan Ketinggian Kawasan Batuan Intrusif Gunung Tanggul Kabupaten Tulungagung

Abstract

Mount Tanggul was formed by a diorite intrusion penetrating limestone, containing quartz, plagioclase, and feldspar minerals that present potential for economic, educational, and tourism utilization. The vegetation in this region serves as an essential biotic element that maintains ecosystem balance. This study aimed to analyze the structure and composition of tree vegetation in the intrusive rock area of Mount Tanggul. The research was conducted in Besuki District from August to September 2022 using a purposive sampling method at three elevation levels: 100, 200, and 300 meters above sea level. At each station, observations were carried out within a 60 m × 20 m transect. Vegetation data for the tree layer were collected using the line method, while pole, sapling, and seedling layers were examined using the line-plot method. Data analysis included the Important Value Index (IVI) and Shannon-Wiener Diversity Index (H′). A total of 21 species from 14 families were identified, with different dominant species at each site: Cocos sp. (Arecaceae) at Station 1, Albizia chinensis (Fabaceae) at Station 2, and Durio sp. (Malvaceae) together with Syzygium aromaticum (Myrtaceae) at Station 3. Diversity values (H′) showed a consistent increase from tree to seedling strata, with the lowest at tree level (H′ = 0.00–1.09) and the highest at seedling level (H′ = 1.62–1.72). These results indicate moderate diversity in regenerative strata but low diversity in the canopy due to species dominance. Vegetation stratification between strata C and B suggests that the community remains at an intermediate successional stage.