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UBC Theses and Dissertations

The impact of altitude, soil geology, and soil depth on Pinus patula solid wood properties for structural timber and plywood production van der Merwe, Jaco-Pierre


Climate is known to impact the growth of plantation forests in South Africa. To characterize the conditions, this study developed temperature and rainfall models for specific plantations in the Lowveld Escarpment and Highveld forestry regions of South Africa. The local climate models use a finer scale than world climate models, and they improve the understanding of how terrain features impact regional climate and historic tree growth. In addition, the finer scale models give insights into the relationship between the local terrain condition and regional climate. Plantation forests were originally established in South Africa to meet an increasing demand for solid wood products as there was a limited supply from native forests. The majority of the commercial softwood plantations were established with Mexican Pinus patula. Since growing conditions are known to impact tree growth, tree form, and wood quality of P. patula, sample plots were established over a cross-section of plantations in the Lowveld Escarpment and Highveld forestry regions of South Africa that covered an array of geologies and altitudes. Soil, growing days, and temperature were found to have little impact on tree form and wood properties. However, rainfall and specifically, spring rainfall, was found to have a highly significant impact on late wood formation, proportion of juvenile core, and wood density. In addition, tree height was found to be strongly correlated with maximum annual temperature. Veneer derived from Lowveld trees had more splitting, which was largely related to defects. Larger trees also had a greater volumetric heartwood percentage and had a smaller live crown height portion, compared to smaller trees. Highveld trees also had greater net veneer recovery and produced better quality veneer than trees grown on the Lowveld. Annual maximum temperature and tree height had a negative relationship with the recovered lumber properties and dimensional stability. Spring rainfall appears to be the most important factor influencing lumber twist and this was possibly due to the associated larger juvenile core present in the trees.

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