Canadian Forest Service Publications
Complex impacts of logging residue on planted hybrid poplar seedling in boreal ecosystems. 2016. Trottier-Picard, A.; Thiffault, E.; Thiffault, N.; DesRochers, A.; Paré, D.; Messier, C. New For. 47: 877-895.
Available from: Laurentian Forestry Centre
Catalog ID: 37389
CFS Availability: PDF (request by e-mail)
We studied three hybrid poplar plantations in Quebec (Canada) established on sites with varying soil and environmental characteristics to investigate the effects of logging residues on the water potential, carbon isotope ratio and foliar nutrients of planted trees. On each site, four treatments representing different residue loads, as well as treatments aimed at manipulating specific factors of the environment (Herbicide, Geotextile) were applied to test their effects on seedling water potential, carbon isotope ratio and foliar nutrients. Along with analyses of variance, we used structural equation modelling to infer causal relationships of logging residues on height, basal diameter and foliar nutrition of trees through their effects on soil temperature, soil water content and competing vegetation cover. Logging residues decreased soil temperature at all sites and woody plants cover at one site out of three. Height, basal diameter and unit leaf mass were strongly related to each other. Foliar δ13C, N concentration and unit leaf mass increased with decreasing cover of woody plants suggesting an important role of competition for resources. Overall, logging residues had no direct influence on hybrid poplar dimensions after two growing seasons: their effects on the microenvironment of this resource demanding tree species were either cancelling out each other, or were not significant enough to have a significant impact on the growth drivers measured. For example, presence of logging residues might reduce soil temperature, impeding overall seedling performance. Our study highlights the fact that any given silvicultural method aimed at manipulating logging residues has a complex influence involving the interaction of multiple environmental drivers and that the net effect on tree productivity will depend on species and site specific conditions.
Plain Language Summary
This study shows that the residues left in logged areas have no short-term (two years) impact on the growth of hybrid poplar seedlings. Logging residues affect a number of factors linked to tree growth. However, these factors can have opposite effects on plants, thereby cancelling themselves out. For example, the presence of logging residues contributes to lowering soil temperature, which in turn stunts tree growth in boreal regions, but, it can also reduce the growth of competing vegetation around the plants, thereby cancelling out its own effects.
The researchers reached these conclusions by studying three hybrid poplar plantations in Quebec. The plantations had variable soil and environmental characteristics, which made it possible to study the impacts of logging residues on the availability of water and nutrients for seedlings.
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