Investigation of methods to determine economic recoverability of timber inventories on a regional basis

Information on the economic recoverability of timber inventories becomes increasingly important as timber harvesting approaches the extensive margin. In British Columbia, as elsewhere in North America, concern for efficient temporal allocation of timber supplies requires a greater understanding of the economic dimensions of timber inventories now and in future years. There are two general categories of problems encountered when attempting to estimate the economic recoverability of inventory. First, there has been a general confusion or misunderstanding of the meaning and measure of economic timber supply. Second, the difficulties associated with measuring inventory recoverability have either discouraged further action or resulted in fairly subjective measures being developed for large regions. In this study, two broad concepts of economic timber supply are discussed; flow, or true economic, supply and stock supply. From this discussion it is shown that a stock-flow supply measure is most suited to forest management needs. That is, periodic stocks of recoverable timber which are adjusted for inflows and outflows that occur between periods as a result of both biological and socio-economic forces. Various uses of stock-flow supply modeling and inventory estimates in forest management are then presented. Next, three alternative means of estimating stock-flow timber supplies are discussed, with reference to previous studies using each alternative: (a) experienced estimates, (b) engineering studies, and (c) statistical models. Reasons are enumerated for further developing the statistical approach, relating the operability of logging to the site, stand and tree characteristics that describes the physical timber inventory. Using data collected from logging operations in coastal British Columbia over the period 1977 to 1979, it is shown that significant relationships can be developed for predicting logging operability, using only those characteristics that are or could be included in inventory records. Specifically, equations are estimated for determining (a) the length of roads required for logging an area, (b) falling and bucking productivity, (c) yarding productivity, (d) scaled volume of logs harvested, and (e) the probability of choosing a specific harvesting system. These equations are then combined with others already developed for stumpage appraisals to illustrate how recoverable stock timber supplies could be estimated. Using current factor costs in British Columbia and log prices on the Vancouver Log Market, an estimate of the 1980 economic inventory was developed for the University of British Columbia Research Forest. Trends in logging costs and log prices in British Columbia were developed, and inventory recoverability on the Research Forest was projected through the year 2000 to illustrate how stock estimates can then be adjusted for temporal flows. It has been concluded that new developments in inventory recording and collating facilities being implemented by the British Columbia Forest Service enhance the feasibility of following simlar procedures on Timber' Supply Areas in the province.Forestry, Faculty ofGraduat