Plant Diversity and Community Structure of Tropical Semi-Evergreen Forests on the Southwest Coast of India

Abstract

This study examines the plant diversity and community structure of a tropical semi-evergreen forest in a sacred grove on the southwest coast of India, encompassing 0.2 hectares. A total of 102 plant species were recorded, including two unidentified orchids. The species composition was categorized into 36 trees (35.29%), 18 shrubs (17.65%), 26 herbs (25.49%), and 22 climbers (21.57%). The forest exhibited a three-layered structure: canopy (>15 m), sub-canopy (8–15 m), and under-canopy (<8 m). The Rubiaceae family was the most diverse, with 8 species, followed by Euphorbiaceae and Verbenaceae, each with 6 species. Species richness generally decreased with increasing diameter at breast height (dbh), with an exception for mature trees over 180 cm dbh. Most species displayed a clumped distribution (approximately 80%), while 6-10% had a random distribution. Tree density varied from 5 to 155 trees per hectare, with a mean of 935 trees per hectare across 36 species. Hemicyclea sepiaria was the most dominant species (Importance Value Index, IVI = 40.50), followed by Manikara hexandra (IVI = 25.19), while Psidium guajava had the lowest IVI (1.73). These results highlight the intricate structure and significant biodiversity of the sacred grove, emphasizing its ecological value and role in conserving tropical semi-evergreen forests.