STRUCTURE CHARACTERISTICS OF HIGH TREE LAYERS OF THE FOREST STANDS WITH Cinnamomum bejolghota (Buch-Ham) Sweet DISTRIBUTION IN SOME NORTHERN MOUNTAINOUS PROVINCES

Abstract

Cinnamomum bejilghota (Buch-Ham) Sweet was naturally distributed in 2 forest status: medium and rich forests with tree density of averagely 755 trees/ha (of which the species had an average of 46 trees/ha) with the number of species ranged from 34 - 85 species and forest volumes from 194.96 to 296.40 m³/ha. The composition of tree layers in the forest status where Cinnamomum bejilghota distributed had 2 dominant communities, which was of Barringtonia macrostachya (Jack) Kurz + Vatica subglabra Merr + Gironniera subaequalis Planch + Terminalia myriocarpa Heurck & Muell. Arg + Cryptocarya densiflora Blume + Cinnamomum bejolghota, and Caryodaphnopsis tonkinensis + Cinnamomum bejolghota + Nephelium chryseum + Pometia pinata, in both of which Cinnamomum bejilghota did not have the largest proportion. The layer structure in the studied forest stands was quite uniform with ( ) varying from 7.07 - 24.30 m, the highest was layer A1 > 20m to layer A2: 10 - 20m and the lowest was A3 layer < 10m. In Hoa Binh and Phu Tho, the species appeared in all 3 layers but was mainly concentrated in A2, then A3 and lowest in A1; in Son La, the species only appeared in A2 but not in A1 and A3. The distribution of Cinnamomum bejilghota by diameter size was simulated by Weibull distribution for forests with its distribution as a decreasing distribution with significance level α = 0.05 (χ_t² < χ₀₅²) with alpha parameter (α) from 0.7 - 1.0"