Tree diversity, community structure and aboveground biomass of a lowland dipterocarp forest of Western Ghats, India

Lowland dipterocarp forests in the Western Ghats are highly biodiverse, structurally complex, and rich in carbon content. To analyse the tree community composition, structure and biomass, we established a 9.9ha permanent forest dynamics study plot in the evergreen forest in Pushpagiri Wildlife Sanctuary of the central Western Ghats, India. All trees ≥ 1 cm diameter at breast height (DBH) were inventoried following the standard of Centre for Tropical Forest Science protocols. Tree diversity across diameter classes and aboveground biomass (AGB) patterns were explored to derive the impact of topography on community composition and AGB in the plot. We recorded a total of 60,454 individuals that belonged to 145 species, 101 genera and 43 families, with Vateria indica (Dipterocarpaceae), Humboldtia brunonis (Fabaceae), and Dipterocarpus indicus (Dipterocarpaceae) being the most prevalent species. Species richness and diversity indices varied and considerably declined with increasing DBH classes. The forest stand exhibited an inverse J-shaped curve, with 90% of the trees having a DBH of less than 10 cm. Seventy-three species (50.34% of total species richness) in the plot were found endemic to the Western Ghats. Of these, Myristica beddomei displayed poor regeneration. The twenty most dominant species accounted for 74.33% of the total abundance. The plot tree density was high with 6086 individuals ha -1 , with a high basal area and AGB of 49.34 m 2 ha -1 and 560.19 Mg ha -1 , respectively. Dipterocarps constitute 39.87% of the overall basal area and 45.19% of the AGB, characterizing a typical lowland dipterocarp forest. The results revealed a significant yet minimal effect of topography on species composition and AGB in the plot. These analyses provide baseline data and crucial insights for the management of evergreen dipterocarp forests, which are rich in endemic taxa. Long-term monitoring of species, through periodic assessments, will be critical to track the ecological dynamics and ensure the effective conservation of these forests.