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An application of the average diameter method of preparing growth tables for lodgepole pine Jewesson, Roy Stanley

Abstract

In the Foothills Region of Alberta lodgepole pine (Pinus contorta var. latifolia) frequently develops even-canopied, undifferentiated stands, the growth of which tends to be controlled by the density of stocking as well as by site and age. In order to consider all these factors, a method for the construction of tables to be used in the prediction of growth of lodgepole pine has been developed. A stand density factor based on basal area per acre and the average stand diameter is introduced and by means of the relationship of these two variables with age a series of basal area growth tables are devised. Similarly, by means of the relationships which stand age and the ratios of total cubic volume and number of trees per acre to basal area per acre, bear to average stand diameter, two more sets of growth tables have been constructed to show the manner in which these ratios progress with age. The site percent concept of describing site is discussed. A table showing the average stand diameter developed by a stand of given age and number of trees per acre on the regional average site was constructed, and the technique of measuring site quality of any individual area by expressing the actual stand average diameter as a percentage of the tabular value is described. The validity of using the site percent method is proven statistically and the method of using this measurement to introduce a site correction into the growth tables is shown. Site variation adds but a small refinement to the prediction of growth for this species, possibly because of an actual small variation in the quality of forest land upon which the species will develop in the Foothills region, or possibly because of a bias in the sample. The techniques discussed are based upon the data from 79 sample plots in the Foothills region of Alberta. While it is believed that the method of deriving the tables and their use is well substantiated by the discussions given, no claim is made for the accuracy of the tables themselves. The data has weaknesses in both the upper and lower classes of age and average diameter and the curves fitted therefrom have suffered accordingly.

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