EFFECT OF THINNING ON GROWTH OF DIFFERENT AGES OF Eucalyptus camaldulensis Dehnh. PLANTATION

Abstract

The role of thinning in Thailand's forest village plantations, Somdet, Kalasin province, was assessed Specifically, the study sought to investigate the post-thinning situation in 4-year old and 7-year-old Eucalyptus camaldulensis plantations, particularly the response of the tree stands. In this case, tree stands with an initial spacing of 2 m x 8 m were thinned to three spacing levels 4 m x 8 m, 2 m x 16 m, and 8 m x 8 m. Application of thinning affected tree growth. Based on the growth parameters: relative growth rate (RGR), net assimilation rate (NAR), leaf area index (LAI) and crop growth rate (CGR), thinning of stands with an original spacing of 2 m x 8 m (S₀) to 4 m x 8 m (S₁), 2 m x 16 m (S₂) and 8 m x 8 m (S₃) showed better growth in both the 4-year-old and the 7-year-old plantation. However, trees in the 7-year-old plantation were found to be more sensitive to thinning than those in the 4-year-old plantation. The trees in the 4 year old plantation showed significant difference only between the highly thinned stand (S₃) and the unthinned stand (S₀), but trees in the 7 year old plantation showed significant differences between the thinned group (S₁,. S₂, S₃) and the unthinned stand (S₀). The study recommends that thinning should not be applied in 4-year-old plantation if the purpose is just to enhance growth of tree stands, but it was shown to be essential in 7-year-old plantation.