Growth performance of indigenous tree species under uneven-aged forest management in Northeast Thailand

For the purpose of conversion of a fast-growing tree plantation into indigenous tree forest in monsoon Asia, growth performances of indigenous tree species under various light conditions were examined. An uneven-aged (two-aged) system in which indigenous trees were underplanted in a fast-growing tree plantation was applied for this conversion on a trial basis in the Sakaerat Silvicultural Research Station, Northeast Thailand. Experimental plots were established from 1987 to 2009 and survival rates and growth in terms of the height of indigenous tree seedlings were examined under various forestry operations (free selection thinning, stripe thinning, group selection thinning in two-aged system, and even-aged system). The results suggest that Dipterocarpus alatus, Hopea odorata, and Dalbergia conchinchinensis could be planted in an open site without a two-aged system. It was recommended that other dipterocarp species (D. turbinatus, H. ferrea, and Shorea henryana) be planted under a two-aged system. Since H. odorata and Xylia xylocarpa var. kerrii adapted to various light conditions, they could be applied to both evenand uneven-aged systems. Group selection thinning was recommended in terms of both the growth performance of the seedlings and the efficiency for logging, when a two-aged system was selected.