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UBC Theses and Dissertations

Product yield and value, financial rotations and biological relationships of good site Douglas fir Dobie, J.


The practice of sustained-yield forest management requires the formulation of management plans designed to ensure the economic efficiency of the forest enterprise. Consequently a knowledge of the volume and value of timber in forest stands is of the utmost importance to foresters engaged in sustained-yield management. In this thesis an analysis of the quantity and value of the product yield from four natural stands of Douglas fir (Pseudotsuga menziesii (Mirb.) Franco) in British Columbia has been made. Average stand ages were 63, 86, 106 and 145 years with heights at 100 years of 160, 165, 175 and 165 feet, respectively. Logging and milling costs for what is regarded as typical coastal British Columbia operations were derived from the literature and from local sources. Lumber yields and values presented were obtained from the results of four mill studies of sample logs from the above stands. Value and volume of plywood and piling products obtainable were ascertained from the literature and from local sources. Linear programming techniques were used to determine the optimum joint-product yield from each of the stands. Financial rotations at two levels of establishment costs, and three interest rates, were examined and mathematical models of the relationship between tree value, tree volume and biological variables are presented. It was found that the net value per cubic foot of tree increased with tree size because of reduced handling costs per unit volume and better quality yield in the larger trees. At the level of costs and values used, and within limits of grade specifications, it is more profitable to produce piling from small trees, and plywood from large trees, rather than lumber. The linear programming solution to optimum product yield indicated that optimum conversion return for all stands was 5 cents per cubic foot greater than the lumber conversion return. Financial rotations, at 3 per cent compound interest on establishment costs and on the value of the growing stock, are between 60 and 70 years for these sites. At 65 years the margin for profit and risk in these stands varied from $1400 to $2000 per acre, increasing with degree of stocking. An increase in establishment costs did not affect the rotation age but reduced the net value per acre of the stand. Increasing the interest rate reduced both the rotation age and the net value per acre of the stand. Many biological variables were found to be significantly correlated with tree value and volume. However, regression models using only two or three variables were statistically as good as, and, from a practical point of view, much better than more involved models. Combinations of dbh, butt-log grade and crown class were the best two or three variable models for value prediction. Tree dbh and D²H rendered similar estimates of board-and cubic-foot volumes. It is considered that the volume and value of timber from these sites could be substantially increased by intensive forest management and complete utilisation of the productive capacity of the land.

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