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UBC Theses and Dissertations

The weibull function as a diameter distribution model for mixed stands of Douglas-fir and Western hemlock Little, Susan Nancy


The three-parameter Weibull function is a satisfactory model of the diameter distributions of mixed stands of western hemlock and Douglas-fir. Weibull distributions estimated by maximum likelihood (MLE) fit eighty of eighty three observed diameter distributions at the ct = .20 level of significance (Kolmogorov-Smirnov test). Weibull parameter predictors are derived by regressing stand characteristics of 42 stands against their MLE parameters. The Weibull diameter distributions predicted from stand age, mean diameter, mean height, site index and trees per acre fit 39 of 41 observed distributions in the test group at the ∞ = .20 level of significance. The results shown here compare favorably with those of other authors. The models given relating stand attributes to diameter distribution will prove useful in stand modeling and in updating forest inventories.

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