An experiment was established at Meldrum Creek in the IDFxm subzone of the Cariboo-Chilcotin region in 1998 to study the effects of reducing aspen density to 0, 1000, 2500, or 4000 stems ha-1 on lodgepole pine performance. After 4 years, when the stand was 10 years old, the treatments had resulted in no significant differences in mean lodgepole pine stem diameter, diameter increment, height, leader length, crown width, or height:diameter ratio (HDR). Survival was at least 92% in all treatments, including the untreated control. One of the objectives of the study was to test and refine competition thresholds for aspen retention on dry-belt IDF sites that had been defined in an earlier study in the Cariboo-Chilcotin (Newsome et al. 2003).
Regression analysis showed that aspen within a 1 m radius of target pine were more important competitors with the pine than aspen farther away. However, aspen competition was relatively unimportant when the stand was 10 years old. The density of aspen that was as tall as, or taller than, target pine predicted, at best, 14.6% of the variation in pine stem diameter increment. At the stand level, reducing aspen density immediately changed the diameter distribution of aspen and reduced its basal area (BA); and, after 4 years, aspen continued to have less basal area than pine in the 0 and 1000 stems ha-1 treatments. Two years after cutting, aspen sucker density ranged from 16 623 stems ha-1 in the 4000 stems ha-1 treatment to 33 599 stems ha-1 in the 0 stems ha-1 treatment. Because of substantial variability in the numbers of suckers counted, however, these differences between treatments were not statistically significant. Sucker densities naturally declined by one-third to one-half between years 2 and 4 after cutting, but still exceeded 8500 stems ha-1.
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Updated May 11, 2007