Thinning compliance and effects on growth and yield of Tectona grandis at Mtibwa forest plantation, Morogoro, Tanzania

A DissertationTectona grandis L.f., a valuable hardwood grown in plantations in about 70 tropical countries. Teak long term market prospects are promising. This study assessed thinning compliance and effects on growth and yield of Teak at Mtibwa forest plantation because there is limited detailed information. Study results will be useful to TFS and other forestry stakeholders with regard to tending operations. The plantation was stratified into 4 age groups (6-10, 11-15, 16-20 and >20 years) capturing all age classes for thinning. Ninety two circular plots of 9.78 m radius were laid out in 23 purposively selected compartments. Compartment thinning history, heights for 3 fattest trees, Dbh and stem quality of all trees in a plot were recorded. Results show 57% and 43% of thinned area is overstocked and understocked respectively as opposed to the thinning schedule. On average, second and third thinnings have significantly higher (P<0.05) SPH deviations of 39% and 26% respectively whereas, first thinnings have 13% (P>0.05) deviations closer to the allowable 10%. Results show that 20% and 80% of first thinnings are delayed for one and two years respectively. Second thinnings are well-timed by 25% but delayed for one and two years by 37.5% each. Third thinnings are delayed for one and two years by 50% each. Site class I results indicate inadequate thinning affects Dbh growth by 6-10% but dominant height is unaffected. Stocking, basal area, and volume are higher by 15-69%, 4-118% and 3-149% respectively. However, VMAI results are lower by 5-26%. Results indicate 73-80% of trees in compartments have stem quality 2. The effect of thinning on stem quality is not established. Compliance to the thinning schedule is recommended to attain the projected mean 40 cm Dbh at rotation age. Future yield predictions for management planning must include relative correction factors ranging from 0.57–2.18