Stand structure and dynamics of young red alder as affected by planting density

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.