Growth and biomass characteristics of a 7 - years old Acacia mangium plantation in Yen Bai province

Abstract

The study was conducted in Yen Bai province to evaluate some characteristics of growth and biomass of Acacia mangium at 7 years old. 16 sample plots (each covering 750 m2) were established and 30 sample trees representing for 5 diameter classes of the forest were cut down for this research. The results showed that, at 7 years old, the average diameter and height of Acacia mangiumplantation in Yen Bai were 13.2 ± 0.23 cm and 14.5 ± 0.14 m respectively; average forest productivity was 13.3 ± 0.57 m3 ha -1 year -1. The current average density of forests is 810 ± 31 trees/ha, of which the percentage of trees with sawn timber diameter (≥15 cm) accounts for only 37% of the total number of trees in the stand. Biomass of individuals of Acacia mangium is concentrated mainly on the trunk (70%), followed by the bark (15%), branches (11%) and the lowest was leaves (4%). The biomass of individual Acacia mangium has a closed correlation with the diameter (D1,3) of the tree (R2 ~ 0.81 ÷ 0.97, P_value <0.0001). The total biomass of Acacia mangium plantation at 7 years old reached an average of 69.9 ± 2.6 tons/ha, of which biomass of A. mangium stand accounted for 86%, litterfall accounted for 8.5% and understory vegetation accounted for 4.8% of the total biomass of the stand. The results of this study are an important scientific basis to propose suitable silvicultural solutions for sustainable management of Acacia mangiumplantation in Yen Bai in particular and Vietnam in general.