Ivan Nielsen

A quantitative inventory of trees in one hectare of mixed dipterocarp forest in Temburong, Brunei Darussalam

One hectare of mixed dipterocarp forest in Temburong, Brunei, was studied in a square one hectare plot. A 5 × 5 metres grid (horizontal projection) was laid out and marked with stakes and strings. All trees ≥ 10 cm dbh were marked with numbered aluminium plates and, for each tree, its coordinates in the plot were marked, its dbh and height were measured, and a voucher was collected for botanical identification. For each species the total and relative densities, dominance, and frequencies, and Importance Value Index (TVI) were calculated. For each family the total and relative values for density, diversity, and dominance, and Family Importance Value (FIV) were calculated. The plot contained 550 individual trees with dbh ≥ 10 cm and these were identified as belonging to 231 species divided among 43 families. The total basal area of trees with dbh ≥ 10 cm dbh was 40.79 square metres. The average height of the trees was 22.5 m, the tallest was 62 m, and the closed canopy was found at 30–40 metres. Dipterocarpaceae ranked highest in FTV with a score of 91.0 (out of 300 possible) followed by Euphorbiaceae with an FIV score of 34.5. The remaining 41 families all had FIV scores of less than 15, the lowest being Dilleniaceae with FIV score of 0.6. Shorea parvifolia (Dipterocarpaceae), Elateriospermum tapos (Euphorbiaceae), Shorea laevis (Dipterocarpaceae) and Gluta laxiflora (Anacardiaceae) were the most important species with IVI values between 18.2 and 12.9 (of 300 possible).