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 f rom three Nelder plots, representing ages 1-7 years and planting densi ties from 238 to 101218 trees ha(-1), were used to develop biomathemat ical models for dominant height, diameter, and survival. The models ac counted for 88-99% of the observed variation in projected height, diam eter, and survival, with planting density accounting for 0.6-2.6% of t he variation in diameter and height and 7.1% of the variation in survi val. Height growth rate exhibited a quadratic relationship with planti ng density up to 24 670 trees ha(-1) and a linear relationship at grea ter planting densities. The natural logarithm of planting density exhi bited a linear relationship with change in relative diameter and quadr atic mean diameter growth rates. These functional relationships betwee n 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 hi gh planting density, annual height and quadratic mean diameter growth were less and reached a maximum at younger ages than at low planting d ensity. The dominant height projection function depicts a temporal rip ple in maximum height growth that progresses outward over time from th e high planting densities in the center of Nelder plots to the lower d ensities near the edge of the plots.