A Finite Mixture Model for Characterizing the Diameter Distributions of Mixed-Species Forest Stands
Abstract:A finite mixture model is used to describe the diameter distributions of mixed-species forest stands. A three-parameter Weibull function is assumed as the component probability density function in the finite mixture model. Four example plots, each with two species, are selected to demonstrate model fitting and comparison. It appears that the finite mixture model is flexible enough to fit irregular, multimodal, or highly skewed diameter distributions. Compared with traditional methods in which a single Weibull function is fit to either the whole plot or each species component separately, the finite mixture model produces much smaller root mean square error and bias, and fits the entire distribution of the plots with extreme peaks, bimodality, or heavy-tails well. In some cases, a single Weibull function fitted to individual species separately may produce more accurate estimations for the component distributions of the two species than the finite mixture model. The summation of the two independent species results, however, may not produce a better prediction for the entire plot. This study shows that the finite mixture model is a promising alternative method for modeling the diameter distribution of multispecies mixed forest stands. For. Sci. 48(4):653–661.
Keywords: Weibull function; environmental management; forest; forest management; forest resources; forestry; forestry research; forestry science; goodness-of-fit test; maximum likelihood; model comparison; natural resource management; natural resources
Document Type: Miscellaneous
Affiliations: 1: Research Assistant Faculty of Forestry, State University of New York, College of Environmental Science and Forestry, One Forestry Drive, Syracuse, NY, 13210, Phone: (315) 446-0980 firstname.lastname@example.org 2: Associate Professor Faculty of Forestry, State University of New York, College of Environmental Science and Forestry, One Forestry Drive, Syracuse, NY, 13210, Phone: (315) 470-6558, Fax: (315) 470-6535 email@example.com 3: Professor Faculty of Forestry, State University of New York, College of Environmental Science and Forestry, One Forestry Drive, Syracuse, NY, 13210, Phone: (315) 470-6569 firstname.lastname@example.org 4: Project Leader Phone: (603) 868-7666 email@example.com 5: Research Forester Northeastern Research Station, USDA Forest Service, Durham, NH, 03824, Phone: (603) 868-7667 firstname.lastname@example.org
Publication date: November 1, 2002
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