Calibrating a Model of Stochastic Effects on Diameter Increment for Individual-Tree Simulations of Stand Dynamics
Abstract:Stand dynamics is the expression of variation in tree and site attributes within the stand operating through the physiologic processes of establishment, accretion, and mortality. Because stand dynamics is the consequence of deviation-amplifying processes, models of stand dynamics should include both variation in processes attributable to known causes as well as to causes that can only be included by stochastic representation of the unexplainable residuum. When the magnitude and serial correlation of unexplained sources of variation in diameter increment are modeled by addition of a random variable, simulated development of both stand volume and spread of diameters are affected. In this report, we develop a model of the tree-to-tree component of unexplained variation that affects stand dynamics. This model is intended for use in individual-tree models of stand development in which time advances in intervals of unequal length. Our model combines results from published time-series analyses with original analyses of residuals from increment models and of measurement variation for diameter increment within individual trees. This eclectic approach is required because extensive data sets do not exist that include adequate samples of the factors known to affect increment and also include information required to model the error structure as well. For. Sci. 39(4):692-705.
Document Type: Journal Article
Affiliations: Research Forester, Intermountain Research Station, USDA Forest Service, Moscow, ID 83843
Publication date: November 1, 1993
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