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A simulation of the tree component of the forest fuel complex to aid in planning for fire control and use McGreevy, Michael G.

Abstract

A model was formulated to estimate tree component weight by geometrically describing the tree with basic tree parameters such as diameter, height, crown width, and crown length and the shape equations that relate them. The stem is divided into three sections with shape equations to describe the wood and bark in each section. The crown is divided into three sections with three equations. The main branch stems are described in three sections by six equations as in the stem. The shapes and their defining parameters provide a volume estimate for the tree components. The density of the wood and bark in each section of the stem and branches is estimated as a random variable. The density of the crown is defined by estimates of interwhorl distances and numbers of branches per whorl, both of which are random variables. The length of the branches also Influences the density of the crown because the weight of the needles and branchlets is a function of branch length. The density and volume of the components combine to give estimates of the weight of the components. In addition to this indirect calculation of tree component weight, the model calculates-the weight of individual tree components with equations having specific tree parameters as independent variables. The estimates of weight are used to calculate the quantity of slash per tree and the center of mass of each major tree component. The weights of the stump and the unmerchantable top are also calculated in conjunction with the slash calculations. The weights and centers of mass are produced in tabular form. The accuracy of the model is limited by the accuracy of the input data. The model was verified for Douglas-fir, western hemlock, and western redcedar. The verification procedure included manual calculations and comparison with other estimates of weight. The model in its present form can aid in understanding the quantitative effects on the tree of variation in the parameters which describe the tree. Because the weight and volume of the tree components influence their combustibility, the model can aid in describing the tree component of the forest fuel complex. New data and further analyses would be needed to determine the full potential and practical utility of the model described herein.

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