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Fortier J.,Fiducie Of Recherche Sur La Foret Des Cantons Of Lest Eastern Townships Forest Research Trust | Truax B.,Fiducie Of Recherche Sur La Foret Des Cantons Of Lest Eastern Townships Forest Research Trust | Gagnon D.,Fiducie Of Recherche Sur La Foret Des Cantons Of Lest Eastern Townships Forest Research Trust | Gagnon D.,University of Regina | Lambert F.,Fiducie Of Recherche Sur La Foret Des Cantons Of Lest Eastern Townships Forest Research Trust
Bioenergy Research | Year: 2015

In this study, we sampled coarse root biomass of three poplar clones in four 13-year-old hybrid poplar (Populus spp.) plantations, with the objective of developing an allometric relationship between diameter at breast height (DBH) and coarse root biomass. A second objective was to test significance of site, clone and ×site clone interaction effects on coarse root biomass, using analysis of covariance (ANCOVA), with DBH as a covariate. Across the four sites, the general allometric relationship between DBH and coarse root biomass was highly significant (R2 = 0.78, p < 0.001). However, given the high significance of the site effect (p < 0.001) in the ANCOVA and the differences in data distribution between sites, two allometric relationships were developed based on the fertility class of sites (high and moderate). Environment-specific allometric relationships developed for two site fertility classes had a better fit (R2 = 0.81-0.90, p < 0.001). ANCOVA, with DBH as a covariate and site fertility class as a main effect, also showed that both of these variables significantly affected (p < 0.001) coarse root biomass allocation. Environment-specific equations showed that higher coarse root biomass was allocated in harsher environments for a given DBH, probably to improve access to growth limiting soil nutrients or to build-up larger storage sites for amino acids and non-structural carbohydrates. Consequently, poplar coarse root biomass growth is both driven by ontogeny (size) and environment, reflecting the plasticity of the root system of mature poplars. Implications of using general vs. environment-specific equations in estimating stand-level root biomass and shoot to root ratios are discussed. Shoot to root ratios calculated using environment-specific equations were more strongly correlated to key environmental variables than ratios calculated using the general equation, with soil NO3 supply rate being the strongest predictor of the ratio (R2 = 0.90, p < 0.001). © 2015 The Author(s) Source


Hamelin C.,University of Regina | Gagnon D.,University of Regina | Gagnon D.,Fiducie Of Recherche Sur La Foret Des Cantons Of Lest Eastern Townships Forest Research Trust | Truax B.,Fiducie Of Recherche Sur La Foret Des Cantons Of Lest Eastern Townships Forest Research Trust
Forests | Year: 2015

The exotic shrub glossy buckthorn (Frangula alnus) is a great concern among forest managers because it invades both open and shaded environments. To evaluate if buckthorn grows similarly across light environments, and if adopting different shapes contributes to an efficient use of light, we compared buckthorns growing in an open field and in the understory of a mature hybrid poplar plantation. For a given age, the relationships describing aboveground biomass of buckthorns in the open field and in the plantation were not significantly different. However, we observed a significant difference between the diameter-height relationships in the two environments. These results suggest a change in buckthorn's architecture, depending on the light environment in which it grows. Buckthorn adopts either an arborescent shape under a tree canopy, or a shrubby shape in an open field, to optimally capture the light available. This architectural plasticity helps explain a similar invasion success for glossy buckthorn growing in both open and shaded environments, at least up to the canopy closure level of the plantation used for this study. © 2015 by the authors; licensee MDPI, Basel, Switzerland. Source


Fortier J.,Fiducie Of Recherche Sur La Foret Des Cantons Of Lest Eastern Townships Forest Research Trust | Fortier J.,University of Quebec at Montreal | Fortier J.,University of Regina | Truax B.,Fiducie Of Recherche Sur La Foret Des Cantons Of Lest Eastern Townships Forest Research Trust | And 4 more authors.
Forestry Chronicle | Year: 2012

In the province of Quebec, approximately 12 000 ha of fast-growing poplar plantations are managed by industrials, while small private landowners have planted only 1000 ha. Most of these poplar plantations are established on clearcut forest sites (approx. 11 000 ha). What are the yields of these hybrid poplar plantations? In this article, available yield data are presented and discussed in the context of a sustainable forest zoning management system. In southern Quebec, three factors are highly correlated to yield for clones of various parentages: NO3 supply rate in riparian soils, elevation (or climate) and soil P availability in abandoned farmland soils. Many Quebec forest sites, particularly in the boreal shield ecozone, have acidic soils and harsh climate, with low mineralization rates. They generally cannot fulfill the very high nutrient requirements of hybrid poplars. Within a forest zoning management system, hybrid poplar plantations and agroforestry should be located in priority in southern Quebec landscapes, with low remaining natural forest cover, and where intensive agriculture is the dominant land-use. This strategy will increase biodiversity and the provision of ecosystem services. Elsewhere, intensive trembling aspen regeneration silviculture could be a sustainable alternative to forest conversion into hybrid poplar plantations. Source

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