SILVICULTURAL CHARACTERISTICS OF Dipterocarpus grandiflorus Blanco IN DAI THANH COMMUNE, DAI LOC DISTRICT, QUANG NAM PROVINCE

Abstract

Dipterocarpus grandiflorus is distributed mainly in evergreen broad-leaved natural forests, where the altitude is < 300 m, the average temperature is 26^oC, the precipitation ranges from 1,796 to 2,015 mm y^-1; and on the yellow-gray or red-yellow ferralite soil, light loam soil texture, slightly acidic soil; soil humus content, total nitrogen, phosphorous and kali varies from 1.68 to 2.09%, 0.11 to 0.14%, 152.26 to 183.34 mg, and 118.17 to 134.86 mg, respectively. The density of canopy layer fluctuates greatly, from 268 to 588 trees ha^-1 depending on the forest state, of which, density of D. grandiflorus is from 4 to 92 trees ha^-1, and are present in the species composition of canopy layer. This species illustrates high significance in ecological aspect with 42.57% of species composition coefficient. The density of regenerated trees of 19-32 species is from 11,000 to 15,160 trees ha^-1, of which, D. grandiflorus only participates in the formula of regenerating trees in the forest state IIIA2 with a coefficient of 7.8%. Density of D. grandiflorus regenerated trees is 480 - 720 trees ha^-1 with the tree height mainly distributes at 1­2m (for state IIA, IIB) and > 2 m (for state IIIA2). The origin of D. grandiflorus regenerated trees is maily by seeds (54.2 - 72.2%) and trees with medium to good quality account for over 70%.