Thesis (Ph. D.)--University of Washington, 2005. / Vita. Includes bibliographical references (leaves 128-139).

Thesis (M.S.)--Oregon State University, 2007. / Printout. Includes bibliographical references (leaves 71-83). Also available on the World Wide Web.

Thesis (Ph.D.)--University of Florida, 2003. / Title from title page of source document. Includes vita. Includes bibliographical references.

Dissertation (doctoral)--Uppsala universitet, 1774. / At head of title: I. H. N. Reproduction of original from Kress Library of Business and Economics, Harvard University. Goldsmiths'-Kress no. 11120.0.

Thesis (doctoral)--Åbo akademi, 1792 and 1795. / Reproduction of original from Kress Library of Business and Economics, Harvard University. Goldsmiths'-Kress no. 15144.2-0.

Thesis (Ph. D.)--University of Texas at Austin, 2005. / Supervisor: Gregory W. Knapp. Vita. Includes bibliographical references.

Thesis (M.S.)--West Virginia University, 2007. / Title from document title page. Document formatted into pages; contains x, 102 p. : ill. Vita. Includes abstract. Includes bibliographical references (p. 84-90).

Thesis (M.S.)--Ohio State University, 2008. / Title from first page of PDF file. Includes bibliographical references (p. 39-43).

Over the past decade the South African forestry industry has gradually experienced the ramifications of labour scarcity, increases in labour costs, the effect of HIV and AIDS and increasing timber demand. Consequently, this has led to an increase in the mechanisation rate, especially in timber harvesting operations. Due to the labour challenges in South Africa, mechanised forestry equipment has increasingly been required to operate in complex forest conditions, such as coppiced compartments, where they have not operated before. It therefore occurs that harvesters are either used in certain coppiced compartments with uncertain productivity expectations, or the harvesters are not used in these compartments due to a lack of productivity knowledge. The influence that certain factors have on harvester productivity and stump volume loss – factors such as coppice regeneration practices and stem form – is poorly understood and has not been quantified. No scientific research exists regarding the effects of coppice compartments on the productivity of a harvester and the amount of stump volume waste. This research aimed at determining the influence of tree volume, tree form, stem felled first and distance between stems on the productivity of an excavator based harvester in coppiced double, coppiced single and planted Eucalyptus grandis pulpwood compartments. Furthermore, the research determined whether there was any stump volume waste, and quantified how much of it was due to excessive stump heights by the harvester. Through regression analysis, productivity equations were derived to make productivity predictions in both coppiced and planted compartments. All stumps were evaluated for waste and the average stump volume waste in coppiced double, coppiced single and planted trees was determined. The research results showed that planted trees had the highest productivity across all tree sizes, followed by coppiced single trees and then coppiced double stems. When harvesting a 0.2 m3 tree, the mean harvester productivity was 8.7 m3 per PMH in coppiced double trees, 13.8 m3 per PMH in coppiced single trees and 16.1 m3 per PMH in planted trees. In coppiced double stems the productivity was not significantly influence by the distance between stems. However, the productivity was significantly influenced by the stem felled first. The regression results showed that if the smaller stem was felled first, the productivity would increase if the larger stem’s volume was less than 0.18 m3; however where the larger stem was greater than 0.18 m3, the relationship was reversed. In addition, the productivity for both coppiced single trees and coppiced double stems were significantly influenced by stem form. The poorly formed trees had low productivity compared to the trees with good form. The stump volume findings showed that coppiced double stems had the highest average stump volume waste per stump, with 0.00307 m3 waste, followed by coppiced single trees (0.001954 m3) and planted trees (0.001650 m3). The average stump volume waste per stump with waste for the planted trees was negligible. This research provides forestry companies and harvesting contractors with information on the effect of tree volume, tree form and stem felled first on harvester productivity in E. grandis coppiced double, coppiced single and planted compartments. This information will assist in making equipment and system selection decisions and improve operational management and control. In addition, they will also be aware of stump volume losses that will occur in the three scenarios.

Permanent sample plots have become the main source of information for estimating models which quantify the dynamic processes of a forest. Fitted models allow for projecting inventories, used to determine timber production and many forest management decisions. The quality of these models is largely dependent on the quality of the information provided by the permanent sample plots. However, the pool of information contained in recent permanent sample plots is limited. Efficient estimation techniques must use all the information available from such plots. Current estimation techniques can be improved. Existing techniques employed in forestry have failed to recognize the random nature of the individual model characterizing each plot. On the other hand, techniques designed for remeasured entities in other scientific fields do not address particular forestry situations such as the small number of remeasurements or the irregularity of remeasurements. A framework for estimating forestry growth models which recognizes the individuality of each plot and special forestry situations is presented in this dissertation. The proposed framework is a two-stage estimation technique, in which the growth rate of a permanent sample plot is considered analogous to the interest rate on a bank account. The first stage estimates the growth rate after removing the time effect. The second stage, based on Von Bertalanffy's growth curve, relates growth rate to site index and volume at the beginning of the growing season. The proposed predictor of future growth rates, the "weighted predictor," is a weighted average between the growth rate observed on a plot and the growth rate predicted from the second-stage model. The weighted predictor is then used to compound the current volume of a plot. An estimate of the variance of the prediction can also be computed. / Forestry, Faculty of / Graduate