Canadian Forest Service Publications
Effect of species composition on the production rate and efficiency of young Picea glauca-Populus tremuloides forests. 2014. Groot, A.; Adhikary, S.; Sharma, M.; Luckai, N.; Bell, F.W.; Larocque, G.R. Forest Ecology and Management 315:1-11.
Issued by: Canadian Wood Fibre Centre
Catalog ID: 35499
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Stand stem volume growth, aboveground tree biomass growth, and site occupancy were measured in 20-year-old mixed stands dominated by white spruce (Picea glauca [Moench] Voss) and trembling aspen (Populus tremuloides Michx.) to examine the effects of species composition on the rate and efficiency of forest production. Measures of site occupancy derived from Plant Canopy Analyzer data indicated that sample plots were fully occupied, and that leaf area index and light interception increased with increasing softwood (SW) proportion. Relationships between site occupancy and SW proportion differed among occupancy metrics, suggesting that basal area, stand density index, and crown area index do not adequately represent use of the light resource. No significant effect of species proportion on the rate of volume or biomass production was detected, contradicting the hypothesis that competitive reduction and facilitation might increase the production of mixed stands. Production efficiency based on light interception for both stand components combined varied weakly with SW proportion. Efficiency metrics based on surrogates for light interception showed differing patterns with SW proportion, underscoring the need for caution in interpreting these metrics in relation to resource use.
Plain Language Summary
We examined 20-year-old white spruce—trembling aspen stands to determine whether the rate and efficiency of forest production was influenced by species proportion. Current ecological theory suggests that mixedwood stands may have a greater productivity because each species uses site resources differently. We measured stand stem volume growth, aboveground tree biomass growth and site occupancy, using a variety of metrics. We found that volume and biomass production did not vary significantly with species proportion because both total light-use efficiency and light interception were similar. We were also able to examine the long-term effects of herbicide application, because our study plots were originally created to test herbicide treatments. We concluded that these herbicide applications did not reduce productivity of the existing aspen component.