| dc.description.abstract | This study was the -first study designed specifically to
analyse the competitive effects of density and species mixture
for both Pinus banksiana and Populus tremuloides
seedlings during the initial stages of growth and development.
To this end, replacement series experiments with jack pine and
trembling aspen seedlings were used in both a greenhouse and
field study. In a 12~week greenhouse pot study species ratios
of 100/0, 75/25, 50/50, 25/75, and 0/100 were planted at
densities of 729, 2,344, and 10,000 pi ants/m In a. field
study, similar mixes were planted at densities of 17, 83, 204,
494, and 2,500 plants/m[superscript]2. This field test will be continued
for a period of three to four growing seasons.
In the greenhouse study, jack pine assumed a dominant
role at the highest density (10,000 plants/m[superscript]2). As the
density was lowered, trembling aspen gained dominance over the
pine in the mixtures. This relationship was reflected in
relative crowding coefficients, as well as in replacement
series diagrams for relattive yield. Also, it was determined
that an adjustment in allocation of biomass with respect to
the dominant competitor occurred. Trembling aspen increased
its percentage biomass allocated to leaf weight, when jack
pine was the dominant competitor. However, the aspen
seedlings allocated a greater percentage to stem weight in
response to aspen assuming the dominant role, A final
observation included the lowering of aspen survival as the
percentage of aspen in mixture increased. Increased density
further accentuated this relationship , Jack pine survival was
consistently high across the range of treatments..
From the preliminary measurements carried out on the
field trial, it was found that both aspen height growth and
crown development were affected by species composition. In
general, as the percentage of aspen decreased at a given
density, both height and crown volume increased. Furthermore,
both height growth and crown volume for jack pine decreased,
as density decreased. The cause for this response to density
was related to the influence of environmental factors. | |
