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0.5-m deep sand beds, which provided hygric, mesic, and xeric conditions for testing all species
and treatments. At the end of nursery growth, an increase in nursery temperature increased height
and height : diameter ratio in all species and shoot:root dry weight ratio in Douglas fir and
lodgepole pine. Increase in temperature also increased the number of seedlings with large wellformed
buds in white spruce, but reduced the number in Douglas fir. Drought stress reduced
height and dry weight in all species and bud length in lodgepole pine. After 9 weeks in sand beds,
low nursery temperature increased survival (19% for lodgepole pine and white spruce grown in
the xeric bed), except for Douglas fir grown in the xeric bed. Nursery drought stress also
increased survival (16% for Douglas fir and lodgepole pine in the xeric bed), but had little effect
on white spruce. Low temperature and drought stress treatments that increased survival also
reduced height and dry weight of lodgepole pine and white spruce after one growing season in
sand beds. Survival showed significant negative correlations with height, dry weight and
height:diameter and shoot : root weight ratios. Low nursery temperature continued to affect
growth 16 weeks after planting, increasing relative growth rate and allometric ratio (K) of
Douglas fir and reducing K of white spruce.
152. Driessche, R.v.-d. 1991b. Influence of container nursery regimes on drought resistance of
seedlings following planting. II. Stomatal conductance, specific leaf area, and root growth
capacity. Canadian-Journal-of-Forest-Research 21(5): 566-572.
Keywords: nursery operations
tree/stand protection
tree physiology
tree/stand health
Abstract: Seedlings of Douglas fir (Pseudotsuga menziesii), lodgepole pine (Pinus
contorta) and white spruce (Picea glauca) were grown in a container nursery from February to
July 1988 and then exposed to three temperatures and three levels of drought stress applied
factorially during mid-July to October 1988. Seedlings were retained in a shelter house until
January 1989, when they were cold-stored until early May. Measurements of stomatal
conductance (gs), transpiration (E), and specific leaf area (SLA) were made at the end of the
treatment period in September 1988 and again after growth the following year at the end of June.
Root growth capacity (RGC) was tested in early May 1989. Results were considered in
conjunction with performance of other samples of the same plants that had been planted in sand
beds in April 1989, where irrigation was regulated to provide three levels of moisture stress. Low
temperature (13 degrees C) generally reduced gs and E, which were adjusted for xylem pressure
potential, and SLA, in all species by the time nursery treatment was completed at the end of
September. No effect of nursery temperature treatment on gs or E could be detected when new
needles were measured in June and July (after 9 to 12 weeks of growth), but SLA of lodgepole
pine increased with nursery temperature treatment, and SLA of white spruce decreased with
treatment. RGC was higher for the 13 degrees C treatment than for the 16 and 20 degrees C
treatments. Survival of outplanted seedlings was mainly inversely related to nursery temperature.
Low nursery temperature reduced gs, E, and SLA and increased RGC. SLA of planted lodgepole
pine increased with level of nursery drought treatment, and severe nursery drought increased gs
under stress, when measured in June. No other effects of drought were detected, although drought
treatment was effective in increasing survival of planted seedlings. It is suggested that other
mechanisms, such as osmotic adjustment, were responsible for the results observed.
153. Driessche, R.v.-d. 1992a. Absolute and relative growth of Douglas-fir seedlings of different sizes.
Tree-Physiology 10(2): 141-152.