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UBC Theses and Dissertations

Determination of economically marginal tree size through the application of conventional and linear programming techniques Valg, Leonid


Various investigators of logging operation efficiency have stated that the harvesting of small trees is inevitably associated with higher operating costs. A comprehensive survey of literature has been presented to substantiate this fact. The cited information was supplemented, for the purpose of this thesis, by a time study conducted at the University Research Forest, near Haney, B. C, in June, 1961. During this study felling, bucking, yarding and loading of timber was studied at two different operations in that Forest. These studies supplied basic data for the computation of the size of the zero marginal tree. It was found that, under existing conditions, the indicated sizes were 12 and 14 in. d.b.h. for Douglas fir and hemlock trees, respectively. Further it was shown that the milling operation constituted the largest cost component, especially penalizing the small dimensions. A new schedule, with certain proposed improvements in operating efficiency, was established. Under this schedule the milling operation was omitted, and the logs were assumed to be the final, marketable product. The solution of this computation revealed that, under the assumed conditions, the zero marginal limit in terms of d.b.h. for Douglas fir and hemlock was lowered to 7 and 8 in., respectively, provided the logs from such small trees could be sold at the same price as # 3 sawlogs. The shape of the net return function suggests, however, that only around and above 15 in. d.b.h. could the operation be regarded as safely paying its way, under current market conditions and restrictions as to minimum log size and length. The technique of linear programming (LP) has been successfully employed in other sectors of manufacturing and transportation. It is demonstrated in this thesis that the LP technique may be applied to certain forest harvesting situations. Progressing through three problem situations of increasing complexity, it is shown how an optimum strategy of action may be established in terms of the economically marginal tree size. The difficulty of obtaining precise time and cost values in sufficient quantity was encountered throughout this work. Consequently, the main purpose of these computations is to illustrate the underlying principles of the application of LP, and to demonstrate its applicability to certain aspects of forest harvesting problems. This area offers wide scope for future investigation and for improvement of techniques.

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