Masters Degrees (Forest and Wood Science)

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Browsing Masters Degrees (Forest and Wood Science) by browse.metadata.advisor "Dash, Jonathan"

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    Calibrating rotation age for eucalyptus pellita and eucalyptus grandis x urophylla to optimize market returns for transmission poles and plywood in Ghana
    (Stellenbosch : Stellenbosch University, 2023-03) Taziwa, Gerald; Ham, Cori ; Dash, Jonathan; Stellenbosch University. Faculty of AgriSciences. Dept. of Forest and Wood Science.
    ENGLISH ABSTRACT: There has been over-reliance on Tectona grandis and Ceiba pentandra for the manufacture of utility poles and plywood in Ghana. Miro Forestry has for the past eight years been growing various tree species including Eucalyptus pellita (Pellita) and E. grandis x urophylla (GU) on large- scale plantations for the first time in Ghana. However, optimum silvicultural regimes and growth and yield models are yet to be defined since the company is in its first full rotation. In this study, the determination of optimal rotation age for Pellita and GU for poles and plywood production was investigated. A combination of the market conditions, processing technology, silviculture regimes and Miro’s existing growth and yield functions were used to determine a suitable rotation age along with appropriate silvicultural treatments. Market analysis for pole size distribution and a plymill experimental study for peeler log processing were the benchmarks used to establish the optimum pole and peeler log specification to satisfy market demand and mill configuration. A taper function was used to calculate the tree size from which these logs can be produced. Once the optimal tree was ascertained, an investigation into the best regime to follow for poles and plywood ensued. This gave guidance on optimum silviculture regimes to grow the ideal tree for poles and plywood. Miro’s existing growth and yield functions within the Microforest software package were used to simulate different thinning scenarios to investigate growth response to thinning. Stocking, thinning intensity and frequency of thinning were altered to test their effect on the growth dynamics of the trees. Rotation age was defined by diameter growth and the time it took to reach the sizes of the optimum pole or peeler log. The results from this study showed that the optimum pole tree had a DBH of 23 cm and a height of 23.3 m. The optimum plywood tree had a DBH of 31 cm and a height of 30.8 m. The simulation results in Microforest showed that a two-thinning regime of 600 stems per hectare gave more favourable results and that GU would achieve diameters of 23 cm for poles at 8.5 years. Pellita would not be able to achieve those diameters even over a much longer rotation. Both species would not achieve the dimensions for an optimum plywood tree within the range of conditions tested. However, the plymill recovery for the smaller diameter class of 15-20 cm was not significantly different from the 20-30 cm class. A tree whose DBH is 21 cm and a height of 21.5 was also ideal for plywood and it produced logs whose average diameter fell within the 15-20 cm diameter class. A two-thinning regime would achieve these dimensions at six years for GU and 11 years for Pellita. GU had a biological and economic rotation of six and seven years respectively. The slower- growing Pellita had a biological rotation of 7.3 years, and the economic rotation was seven years. This study illustrates that when markets demand very specific product dimensions, the use of biological and economic rotation ages would be subservient to technical rotation age.