The diversity of 15 ha of lowland mixed dipterocarp forest, Central Kalimantan

Fifteen hectares of primary forest in Central Kalimantan were enumerated and all trees ≥10 cm dbh tagged and identified to species as far as possible. Tree density, relative abundance of families and species diversity were calculated, as was a mean additive species/area curve for 1 ha and a species/area curve for all 15 ha. The Jaccard index of similarity was also calculated for the 15 plots. The 15 ha enumerated contain 8771 trees with a dbh of ≥10 cm, belonging to 1298 ‘morphospecies’ in 56 families. On average a single plot had 583 trees and 205 species. These figures are within the upper range of species diversity for the Malesian region as a whole. Dipterocarpaceae make up 14% of all trees in the plots, closely followed by Euphorbiaceae with 13%. A surprisingly low coefficient of similarity is found between the plots, the lowest being 3% and the highest 30%. Species/area curve construction showed that the asymptote is not reached in any of the 1 ha plots or when the 15 plots are added together.