Effects of thinning on growth performance of teak (Tectona grandis) plantations in Tain II Forest Reserve, Ghana

Abstract

Although recent interest in commercial teak plantation establishment has soared, knowledge of intensive silvicultural management of residual stands is limited in most parts of West Africa. This study evaluated the effects of thinning regimes on the growth responses and pruning requirements of teak plantations, two years after thinning, in the transition zone of Ghana. The thinning trial was conducted on a 4-year-old stand with initial stocking of 1 111 trees ha⁻¹ in the Tain II Forest Reserve, Ghana. The treatments were four thinning regimes: 50%, 30%, 0% thinning intensities and 50% decrowning, arranged in a completely randomised design with four replicates. Two years after thinning, the treatments were significantly different in diameter at breast height (DBH) (p < 0.00029), total height (p = 0.017) and stem density (p < 0.0002). The 50% thinning intensity had the highest mean tree DBH, volume, height and basal area of 15.57 cm, 0.13 m³, 11.94 m and 0.02 m² respectively. The lowest was found in the control (no thinning) except height which was least in decrowned plots. Maximum mean annual increment of DBH, total height and volume were respectively 2.00 cm, 1.34 m and 9.9 m³ ha⁻¹ for the heavily thinned stand. The number of epicormic shoots per tree increased with the thinning intensity/regime, hence increasing the pruning requirement. It is concluded that 50% thinning intensity promotes positive growth of residual stand but increases the pruning requirements and possibly the pruning costs. Long-term evaluation of this trial is essential to validate the recommendations from this study.