Effects of Thinning on Growth, Yield and Stem Quality of Pinus patula at Sao Hill Forest Plantation, Mufindi District, Tanzania

Abstract

Pinus patula is one of the most important plantation species grown in Eastern and Southern Africa. Its growth rate and yield vary considerably depending on site conditions, management techniques and genetic quality of the trees. It has been suspected that thinning of softwood plantations in Tanzania has been neglected resulting in lower standing volume being distributed into many small trees of poor form. This study assessed the effects of thinning on growth, yield and stem quality of Pinus patula at Sao Hill Forest Plantation located in Southern Highland part of Tanzania. In a systematically established plots; diameter of all trees, a total height of three trees and stem quality of four classes were recorded. An independent t-test was used to test for significant difference in stand parameters and Mann-Whitney U test was used to test stem quality between thinned and unthinned stand. Results showed that thinning significantly increased growth and yield of Pinus patula. Thinning improves stem quality by 9% resulting in trees having straight and good stem form. Thinned stands yielded higher volume than unthinned stands. Therefore, this study recommends that pine plantations should be timely thinned as per used thinning schedule to ensure that more volume is attained.