Structural characteristics and gap size distribution of the hill evergreen forest at Doi Pui, Chiangmai [Thailand]
1985
Mongkon Vannaprasert
Trees were divided into three categories: trees with equal or more than 4.5 cm in DBH (category I), but taller than 1.30 m in height (category II) and trees less than 4.5 cm in DBH, and below 1.30 m in height (category III). The latter two categories represented the regenerated tres in the canopy gap. The results of the study showed that the maximum number of species, basal area, average tree height and diversity were found in the category I while the highest density was found in the category III. The most important tree species as determined by IVI was Castanopsis acuminatissima in the first category I, Lisea monopetal in the category II and Phoebe lanceolata in the category III. The vertical structure of the category I was precisely divided into three layers, above 29.70 m, 21.30-29.70 m and below 21.30 m. Moreover, the third layers can be subdivided further into two sublayers at 15.75 m. Dispersion pattern of all trees in the first category was random but was contagious for the four important tree species; Castanopsis accuminatissima, Duranta repens, Ardisia vestita and Castanopsis ferox. Twenty six gaps were found in the 3 ha. study area. Their maximum size was 1236 m2 and the total gap area was 16.76 percent or 5028 m2 of the study area. The relative illuminance at ground level increased with increasing canopy gap size. The geometric mean of relative illuminance at ground level; was 3.73 percent of full sunlight. The maximum number of species and diversity of the second and the third categories were found in the small canopy gap while the highest density of the second and the third categories were found in the biggest canopy gap
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