Effect of thinning on growth and yield of Acacia mangium-Dipterocarpus alatus mixed plantation

Wachrinrat, Chongrak and Khlangsap, Somphat and Paungchit, Ladawan and Teejuntuk, Sakhan and Jamroenprucksa, Monton (2005) Effect of thinning on growth and yield of Acacia mangium-Dipterocarpus alatus mixed plantation. [Conference or Proceeding]

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Abstract

A study on the effect of thinning on the growth and yield of Acacia mangium and Dipteocarpus alatus was carried out in mixed stand of 5-year-old A. mangium and D. alatus at the Forest Industry Organization Takum Plantation, Trat Province. The data was collected in 2003, 2004 and 2005. The experimental design is randomized completely block design with three treatments and three replications: no thinning, 50% thinning and clearcutting. Each plot was 15 m x 30 m. The sample trees were cut to estimate various parts of aboveground biomass through allometric correlation to estimation of stand biomass. The growth of trees were measured and calculated two tears after thinning. The results showed that the average total stem biomass, commercial stem biomass, branch biomass and leaf biomass of 5-year-old A. mangium were 128.9, 127.2, 19.1 and 7.4 kg tree-1 or 59.7, 58.9, 8.8 and 3.4 t ha-1, respectively. The average total stem volume and commercial stem volume were 0.236 and 0.227 m3 ha-1 or 109.3 and 105.2 m3 ha-1, respectively. Thinning levels affected the growth of trees in terms of current annual increment (CAI) and relative growth rate (RGR) of diameter at breast height and height. It was showed that CAI and RGR in thinning plots were higher than no thinning plots. In addition, RGR of biomass of A. mangium also showed the same trend. However, D. alatus was found to be more sensitive to thinning levels than A. mangium. The study concluded that for short and long rotation species mixed planting, the thinning of 5 to 6-year-old short rotation species is recommended for increasing the growth rate and yield of trees.

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