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Data from an eastern cottonwood clonal mixing study in Mississippi and Kentucky, USA, were used to test the effects of planting locations and genetics (clonal proportions) on height–age and height–dbh functions. Planting locations, which accounted for 5.6% of the variation in observed dominant height growth ( p =0.0001), were more important than clonal proportions, which accounted for only 1.0% of the variation ( p =0.0077). Interactions between clones in mixtures were not significant ( p =0.9178), but three cases of over- and undercompensation paralleled those observed for basal area. Planting locations were associated with differences in maximum height in the height–dbh function and clonal proportions were associated with differences in height of trees with smaller than average dbh. Although statistically significant, the effects of planting locations and clonal proportions were not important enough to incorporate into the final height–dbh model.

A red alder planting spacing study was used to compare three modeling approaches that have been successfully used for other tree species. These three approaches predict stand structure and dynamics in plantations that are 7 to 16 years old, with planting densities of 976 to 13 899 trees/ha. The diameter-distribution-prediction approach tended to over-predict the diameter at breast height (dbh) for larger trees in stands planted at low density and to under-predict dbh for smaller trees in stands planted at high density. This approach may be useful for comparing planting densities when a tree list is not available. The stand-table-projection approach tended to under-predict dbh for smaller trees in young stands planted at low density and to over-predict dbh for smaller trees in young stands planted at high density. This approach, however, provided consistency between stand- and tree-level growth projections, and should be useful for comparing planting densities when a tree list is available. The individual-tree-growth approach provided the best representations of observed diameter distributions at all planting densities, stand ages, and growth intervals. This approach may be best suited for stands that have been thinned, stands with mixtures of species, and stands with heterogeneous size classes.

The response of stand structure and dynamics of young red alder ( Alnus rubra Bong.) was examined over a gradient in planting density. Data from three Nelder plots, representing ages 1–7 years and planting densities from 238 to 101 218 trees ha −1 , were used to develop biomathematical models for dominant height, diameter, and survival. The models accounted for 88–99% of the observed variation in projected height, diameter, and survival, with planting density accounting for 0.6–2.6% of the variation in diameter and height and 7.1% of the variation in survival. Height growth rate exhibited a quadratic relationship with planting density up to 24 670 trees ha −1 and a linear relationship at greater planting densities. The natural logarithm of planting density exhibited a linear relationship with change in relative diameter and quadratic mean diameter growth rates. These functional relationships between growth rates and planting density were consistent with the concepts of competition thresholds: height and diameter growth rates were more affected by planting density at lower than at higher planting density while mortality rate increased linearly with increasing density. At high planting density, annual height and quadratic mean diameter growth were less and reached a maximum at younger ages than at low planting density. The dominant height projection function depicts a temporal ripple in maximum height growth that progresses outward over time from the high planting densities in the center of Nelder plots to the lower densities near the edge of the plots.

Height-age and height-diameter models for plantations of young Douglas-fir ( Pseudotsuga menziesii [Mirb.] Franco var. menziesii ) were examined in relation to vegetation management treatments. The models were developed from 10 years of measurements in a competition release study installed on six sites in the Coast Ranges of Oregon and Washington. Analysis of height growth patterns for dominant trees indicated significant differences between the total vegetation control treatment and operational release treatments or no treatment. The resulting height-age function depicted exponential growth patterns for the total vegetation control treatment and nearly linear patterns for the operational release treatment and no treatment. The height-diameter function was compatible with dominant height growth and quadratic mean diameter prediction functions. Different height-diameter curve shapes were associated with total vegetation control and the operational release and no treatments. The resulting function implied that Douglas-fir trees of a given diameter and age were slightly taller when under interspecific competition, especially for trees with smaller diameters. The height-age and height-diameter functions may be used in conjunction with diameter distribution or stand table projection models developed for those data to predict dynamics and stand structure in young Douglas-fir plantations.

A stand table projection system based on individual-tree and stand-level models for young Douglas-fir ( Pseudotsuga menziesii (Mirb.) Franco var. menziesii ) plantations was developed from and evaluated with remeasurement data from sites in the Siskiyou Mountains of southwestern Oregon and in the Coast Ranges of Oregon and Washington. A projection equation was developed for relative tree size, defined as the ratio of individual-tree diameter at 15 or 30 cm above ground level (depending on the study location) to quadratic mean diameter. The relative size projection equation for the Coast Ranges study included the effect of total vegetation control, which indicated that diameters of Douglas-fir receiving total vegetation control tended to become more uniform over time in the Coast Ranges. An additional equation was developed to project quadratic mean diameter so that individual-tree diameters could be estimated from projected relative size. The effect of vegetation management treatments on projected quadratic mean diameters in the Siskiyou study was expressed as an interaction between proportion of cover removed by treatments (intensity) and dominant height of Douglas-fir at time of treatment relative to current dominant height. In 1- and 2-year projection periods, the stand table projection system performed similarly to a diameter distribution prediction system based on a Weibull distribution function. However, the difference between projected and predicted diameter distributions became more pronounced as the projection period increased to 5 years.