Effects of low levels of dispersed retention on the growth and survival of young, planted Douglas-fir
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Issue Date
2012
Editor
Authors
Smith, Nicholas J.
Beese, William J.
License
Attribution 3.0 Unported (CC BY 3.0)
Subject
Abstract
Three large-scale, experimental, dispersed residual tree sites established in coastal
British Columbia, Canada were measured for planted Douglas-fir tree growth and survival
five to six years after planting. The dispersed trees were predominantly large diameter
(60 cm+) Douglas-fir left with a range of 0% to 30% of the original forest stand basal area
(0 m2 ha-1 to 14 m2 ha-1). Two sites had 0%, 5% and 15% retention, while one site had 0%,
5%, 10% and 30% retention. The trees were measured in sector plots established to randomly
sample the range of microsites in each treatment. There was no detectable difference between
height and basal diameter growth or mortality rates between the retention treatments over the
measurement period, except for a reduction of basal diameter growth at the 30% retention
level (p < 0.05). Thus a statistically significant impact on growth was demonstrated for the
30% retention compared to the 0% retention level. We expected intermediate growth rates
between the 0% and the other lower retention levels but were unable to demonstrate this
due to the low statistical power of the test (10 observations) and high site variability for
these very young trees.