| dc.description.abstract | The objectives were: to review the successional behaviour of
white spruce (Picea glauca (Moench) Voss) - trembling aspen (Populus
tremuloides Michxt) stands in the literature, to conduct field studies
of the successional behaviour of planted white spruce in aspen stands,
and to test hexazinone herbicide as a means of modifying the postlogging
environment to release white spruce and other conifers.
Five and 13 year old white spruce plantations were selected
for study. Fifty square random plots were established in each
plantation. Total and mean aspen and white spruce volumes per plot
were calculated. Each plantation was stratified into 3 components
or "Situation Types" based on aspen density. Five plots were
established at both plantations in each of these Types. These
"Situation Plots" were circular and selected so that a white spruce
tree was located at each plot centre. The central white spruce and
the mean aspen tree on each "Situation Plot" were cut down for stem
analysis. The number of frost damaged tips per m[superscript 2] crown area on each central white spruce tree were calculated.
The mean and total aspen volumes per plot are not related to
the white spruce volumes per plot in either plantation. The current
annual increment curves of the paired central white spruce and the
mean aspen tree from each "Situation Plot" do not show any trends
for the 5 year old plantation. Current annual volume increment
curves from the 13 year old plantation show that a rapidly growing
aspen tree will suppress its white spruce neighbour. The number of
frost damaged tips per m [superscript 2] white spruce crown area significantly decreases as the number of aspen trees per plot increases at the 5 year old plantation. This relationship was not strong at the 13
year old plantation.
This information is used to make recommendations for releasing
white spruce from trembling aspen competition with hexazinone
herbicide.
Factorial herbicide trials were established in the field and
greenhouse to evaluate the effect of hexazinone herbicide on white
spruce and trembling aspen. Trials were also established to evaluate
the effect of hexazinone on black spruce (Picea mariana (Mill.)
B.S.P.), jack pine (Pinus banksiana Lamb.), willow (Salix spp.) and
beaked hazel (Corylus cornuta Marsh.) , Various hexazinone rates,
forms, spacings and spray positions were tested. Hexazinone
'Gridball' pellets and hexazinone concentrated solution (DPX-LX or
LE) were the herbicide forms used.
White spruce, black spruce and jack pine were found to be quite
tolerant to hexazinone herbicide. Hexazinone did not reduce the
survival or height growth of the white spruce significantly except
in the greenhouse trial. Jack pine and black spruce were only
significantly affected at the highest rates. In the greenhouse
trial, the high hexazinone rates applied to the foliage and soil
significantly reduced the survival and the foliage dry weight of
both white spruce and jack pine. Most rates of hexazinone applied
caused a significant reduction in height growth, survival and
foliage dry weight of the aspen, willow and hazel.
These results suggest that hexazinone can be used effectively
to control weed species in conifer plantations. | |
