The Clusko aspen removal study, established in 2001 in an 11-year-old lodgepole pine-trembling aspen stand in the SBPSxc subzone, investigates the effects of five levels of aspen removal on target pine, neighbourhood competitive interactions, and stand development. Treatments include: (1) an untreated control; (2) complete aspen removal; broadcast retention of (3) 1000 and (4) 2500 aspen stems ha-1; and (5) a spatial treatment that removed aspen within a 1-m radius around target pine.
Two years after treatments were applied, 2001-2003 target pine stem diameter increment was significantly larger in the 0, 1000, and 2500 stems ha-1 removal treatments than in the uncut control. In 2003, target pine stem diameter was significantly larger in the complete aspen removal treatment than in the control, and height:diameter ratio was smaller. Aspen removal treatments had no significant effect on lodgepole pine height, leader length, or crown width within 2 years of treatment.
Regression analysis showed that when the stand was 13 years old, lodgepole pine stem diameter growth decreased with increasing density of aspen that were at least as tall as the target pine. The relationship was strongest where aspen were included within a 2.56-m radius plot, which was the largest neighbourhood examined in this study, and was not statistically significant in neighbourhoods with smaller radii. At age 13, tall aspen density accounted for a maximum of 21.2% of the variation in pine growth, with the strongest relationship occurring between 2-year pine stem diameter increment (2001-2003) and 2003 tall aspen density. At the stand level, reducing aspen density immediately changed the diameter distribution of aspen and reduced its basal area, although after 2 years aspen continued to have greater basal area than pine in all but the complete aspen removal treatment. Two years after cutting, aspen sucker density had decreased significantly with the level of aspen retention. Complete aspen removal resulted in an average density of approximately 93 000 suckers ha-1 after 2 years, compared with approximately 44 000 and 22 000 suckers ha-1 in the 1000 and 2500 stems ha-1 retention treatments, respectively.
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Updated May 11, 2007