Complex impacts of logging residues on planted hybrid poplar seedlings in boreal ecosystems

Published in New Forests 47(6): 877–895

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 d¹³C, 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.

Forests

Scientific Article

Forestry Research, Forests, Silviculture

TROTTIER-PICARD, Amélie, Évelyne THIFFAULT, Nelson THIFFAULT, Annie DESROCHERS, David PARÉ and Christian MESSIER

2016

Available at the Direction de la recherche forestière

analyse de pistes, peuplier hybride, résidus de coupe, potentiel hydrique, nutriments foliaires, isotope du carbone, sylviculture et rendement des plantations, article scientifique de recherche forestière, populus, silviculture and yield of plantations, structural equation modelling (SEM), hybrid poplar, forest logging residues, water potential, foliar nutrients, carbon isotope