Diversity and Ecology of Tree Species on Netaji Subash Chandra Bose Island (Ross Island), Andaman Islands, India

ABSTRACT This study documents the diversity, structure, and ecological characteristics of tree species on Nataji Subash Chandra Bose Island, Andaman Islands, India. A total of 23 tree species, representing 17 genera and 11 families, were recorded from 20 m × 20 m quadrats. The tree flora is dominated by dicotyledonous species, with only two monocotyledonous species; the genus Ficus is particularly well represented, with seven species, while the remaining 16 genera are monospecific. Climatic observations during the study period indicate deviations from long‑term records, including reduced rainfall coinciding with slightly increased mean temperature, which may affect the ecological balance of the island’s tropical evergreen forests. Sediment properties showed persistently acidic pH and marked seasonal variation in nutrients: nitrogen, phosphorus, and potassium reached minimum levels during the monsoon, likely due to leaching, and peaked in the post‑monsoon months when accumulated litter and biomass decomposed, consistent with trends in organic carbon. Phytosociological analysis revealed that Casuarina equisetifolia and Cocos nucifera attained the highest Importance Value Index (IVI), reflecting their ecological dominance, while Cocos nucifera, Azadirachta indica, Casuarina equisetifolia, and Terminalia catappa showed the highest Total Importance Values (TIV), indicating multiple uses to local communities. Shannon diversity (H′) for tree species was 3.46 and Gleason species richness (SR) was 3.98, indicating relatively high diversity and richness for a small island, although lower than values reported for larger Andaman islands. Notably, seedlings and saplings of the recorded tree species were absent, probably due to low light under a dense canopy combined with heavy browsing by spotted deer. The tree population is dominated by long‑lived individuals, and opportunities for further forest expansion are limited by topography and shoreline erosion. These findings highlight the need for integrated conservation and shoreline protection measures to maintain the ecological integrity of Nataji Subash Chandra Bose Island’s forests. Keywords: tropical evergreen forest; phytosociology; species diversity; coastal erosion; regeneration; Andaman and Nicobar Islands