Database development and application to characterize juvenile Douglas-fir (Pseudotsuga menziesii [Mirb] and understory vegetation in the Oregon and Washington Coast Range Mountains

Graduation date: 1998The Regional Vegetation Management Model (RVMM) predicts the effects of associated vegetation on the growth and yield of young Douglas-fir (age [less than or equal to] 20 years) in the Pacific Northwest, and is a 'front-end' growth model for existing rotation-age growth models. Objectives of this thesis are to: (a) document development of the Coast Range RVMM database, (b) characterize tree and vegetation attributes in the database, (c) describe static tree-level equations used to complete the Coastal RVMM database, and (d) describe a Douglas-fir juvenile-stand height potential index. Database. Development of the Coastal RVMM database is described with\ud respect to the underlying design matrix, sampling and data collection protocols,\ud extent and location of growth monitoring plots, and attributes of trees (conifer and hardwood) and associated vegetation (herb and shrub). Ninety-eight growth monitoring plots were established in the Coast Range Mountains of Oregon and Washington across a sampling matrix defined by site quality, tree-size and species, and extent and size of associated vegetation. Static Tree-Level Equations. Development of static tree-level equations to predict tree-level attributes sub-sampled during data collection is described. Equation forms have a basis in biometric literature, although each were uniquely adapted for specific tree performance. Thirty-six prediction equations are described for Douglas-fir, three other conifer species, and six hardwood species\ud for: single-stem diameter, multi-stem basal area, tree height, crown width, and dbh-d15 relationship. The prediction equations produce unbiased estimates of tree-level attributes with adjusted R² values ranging from 0.46 to 0.93. Juvenile-Stand Height Potential Index. Douglas-fir juvenile-stand height potential index (HPI) was developed using the Coastal RVMM dataset, but augmented with four other datasets to extend database stand age (1 to 36 years breast-height-age) and. site quality. The HPI equation is an algebraic-difference formulation of an exponentiated and generalized Schumacher growth equation. In comparison with existing site-index equations: (I) HPI represents greater dominant height growth to about breast-height age 20 years, and (ii) site quality\ud is predicted more consistently across the entire breast-height-age range of the\ud database