Masters Degrees (Forest and Wood Science)

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Browsing Masters Degrees (Forest and Wood Science) by Author "Charlton, Ryan A."

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    Higher initial planting densities for South African-grown Pinus patula sawlog trees: the effect on stem form and land expectation value
    (Stellenbosch : Stellenbosch University, 2018-03) Charlton, Ryan A.; Wessels, Brand; Ham, Cori; Stellenbosch University. Faculty of AgriSciences. Dept. of Forest and Wood Science.
    ENGLISH ABSTRACT: There are concerns that the modulus of elasticity (MOE) of Pinus patula lumber in South Africa has decreased mainly due to faster growth and reduced rotation ages. However, a number of recent studies have shown that increased planting densities can improve mean stiffness of wood from several softwood species. Additionally, stem form could possibly also improve with higher planting densities. The objectives of this study were to evaluate the effect of Pinus patula saw log management regimes, based on higher initial planting densities, on land expectation value (LEV) and stem form. Stem form has a large influence on volume and value recovery in sawmills and the influence of stem form characteristics can be considered when calculating log values using software programmes such as Simsaw. This study was conducted using an 18 year-old Pinus patula experimental spacing trial. The trial was located near Barberton on the Mpumalanga escarpment. The experiment consisted of two replications of four planting densities (403, 1 097, 1 808, and 2 981 spha). Stem form characteristics (ovality, straightness, sinuosity, butt-flare, and taper) from each spacing treatment were assessed from Lidar scanning data. The trial was felled and logs processed into structural size lumber which were destructively tested for MOE and modulus of rupture (MOR). The board MOE, together with sawing simulation results, were used to assign a log value recovery to each log class from each spacing treatment. Together with South African forestry cost data, the land expectation value for a range of planting density treatments and thinning regimes were calculated. Spacing treatment had a significant effect on all five stem form characteristics. Over the bottom nine meters of the stem, the lower spacing treatments (403 and 1 097 spha) had mean stem deviations of 132.1 mm and 109.3 mm respectively while the higher planting densities (1 808 and 2 981 spha) had mean stem deviations of 76.4 mm and 82.1 mm respectively. Taper and butt-flare also had a decreasing trend from 403 spha to 2 981 spha. Ovality, on the other hand, increased with increasing planting density and also increased with increasing height along the tree stem. There was an increase in mean MOE of lumber with increasing planting density. Similarly, the structural grade recoveries of similar board positions increased with planting density. This, in turn, resulted in increased log value recovery, for the same log sizes, with increased planting density. The best management regimes for each of the three lower planting densities (403, 1 097, and 1 808 spha) all returned LEV values relatively close to each other. The best LEV was from a spacing treatment of 1 808 spha, thinned at 12 years to 300 spha, and clearfelled at 19 years (R47 693.02/ha. The second best management regime was for the 1 097 spha planting density, thinned to 250 spha at 13 years, and clearfelled at 18 years (R46 677.59/ha). Despite the results showing that higher planting densities result in better value recoveries for the same log sizes, the best LEV was not obtained from the highest planting density but with a medium high planting density and a late thinning.