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Equations for Predicting Uncompacted Crown Ratio Based on Compacted Crown Ratio and Tree Attributes

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Equations to predict uncompacted crown ratio as a function of compacted crown ratio, tree diameter, and tree height are developed for the main tree species in Oregon, Washington, and California using data from the Forest Health Monitoring Program, USDA Forest Service. The uncompacted crown ratio was modeled with a logistic function and fitted using weighted, nonlinear regression. The models were evaluated using cross-validation. Mean squared error of predicted uncompacted crown ratio was between 0.1 and 0.15, overall bias was negligible, and correlation between the predicted and observed uncompacted crown ratio was high for most species. The sensitivity of crown fire risk to crown ratio estimation method was evaluated using the Fire and Fuels Extension of the Forest Vegetation Simulator. Torching index, an estimate of the wind speed needed for a crown fire to develop, was significantly greater when compacted crown ratio was used instead of uncompacted crown ratio. The close agreement in torching indices simulated using predicted and observed uncompacted crown ratio provides further evidence of the utility of the models developed in this study. West. J. Appl. For. 19(4):260–267.
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Keywords: Crown fire risk; cross-validation; crown base height; environmental management; forest; forest management; forest resources; forestry; forestry research; forestry science; natural resource management; natural resources

Document Type: Regular Article

Affiliations: 1: Forest Inventory and Analysis USDA Forest Service PNW Research Station P.O. Box 3890 Portland OR 97208 Phone: (503) 808-2047;, Fax: (503) 808-2020, Email: 2: Forest Inventory and Analysis USDA Forest Service PNW Research Station P.O. Box 3890 Portland OR 97208

Publication date: 2004-10-01

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  • Each regional journal of applied forestry focuses on research, practice, and techniques targeted to foresters and allied professionals in specific regions of the United States and Canada. The Western Journal of Applied Forestry covers the western United States, including Alaska, and western Canada; WJAF will also consider manuscripts reporting research in northern Mexico that has potential application in the southwestern United States.
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