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Regos A.,InForest Joint Research Unit | Aquilue N.,InForest Joint Research Unit | Aquilue N.,Center Detude Of La Foret Cef | Retana J.,InForest Joint Research Unit | And 2 more authors.
Ecosystems | Year: 2016

Increases in fire impacts over many regions of the world have led to large-scale investments in fire-suppression efforts. There is increasing recognition that biomass extraction for energy purposes may become an important forest-management practice in fire-prone ecosystems. However, at present, very few studies have explicitly assessed biomass extraction as a fuel treatment at landscape scale. Here, we use a landscape fire-succession model in Catalonia (NE Spain) to quantitatively evaluate the potential effects of a biomass extraction-based strategy on essential fire-regime attributes after considering different levels of fire suppression, biomass extraction intensity, and spatial allocation of such efforts. Our simulations indicated that the effectiveness (area suppressed in relation to expected area to burn) at suppressing wildfires was determined by extraction intensity, spatial allocation of the extraction effort, and the fire-suppression levels involved. Indeed, the highest suppressed-area values were found with lower harvesting intensities, especially under high fire-suppression capabilities and strategies focused on bioenergy goals (figures close to 0.7). However, the leverage (area suppressed in relation to managed area) was higher when the treatments were based on the fire-prevention strategy and focused on high-fire-risk areas (up to 0.45) than with treatment designed for energy reasons (lower than 0.15). We conclude that biomass extraction for energy purposes has the potential to induce changes in fire regimes and can therefore be considered a cost-effective landscape-level fuel-reduction treatment. However, our results suggest that large-scale biomass extraction may be needed if significant changes in fire regimes are to be expected. © 2016 Springer Science+Business Media New York


Trottier-Picard A.,Center Detude Of La Foret Cef | Trottier-Picard A.,University of Québec | Thiffault E.,Laval University | Thiffault N.,Center Detude Of La Foret Cef | And 6 more authors.
New Forests | Year: 2016

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. © 2016 Springer Science+Business Media Dordrecht


Beguin J.,Laval University | McIntire E.J.B.,Center Detude Of La Foret Cef | McIntire E.J.B.,Natural Resources Canada | Raulier F.,Center Detude Of La Foret Cef | Raulier F.,Laval University
Journal of Environmental Management | Year: 2015

Protected area networks are the dominant conservation approach that is used worldwide for protecting biodiversity. Conservation planning in managed forests, however, presents challenges when endangered species use old-growth forests targeted by the forest industry for timber supply. In many ecosystems, this challenge is further complicated by the occurrence of natural disturbance events that disrupt forest attributes at multiple scales. Using spatially explicit landscape simulation experiments, we gather insights into how these large scale, multifaceted processes (fire risk, timber harvesting and the amount of protected area) influenced both the persistence of the threatened boreal caribou and the level of timber supply in the boreal forest of eastern Canada. Our result showed that failure to account explicitly and a priori for fire risk in the calculation of timber supply led to an overestimation of timber harvest volume, which in turn led to rates of cumulative disturbances that threatened both the long-term persistence of boreal caribou and the sustainability of the timber supply itself. Salvage logging, however, allowed some compensatory cumulative effects. It minimised the reductions of timber supply within a range of ~10% while reducing the negative impact of cumulative disturbances caused by fire and logging on caribou. With the global increase of the human footprint on forest ecosystems, our approach and results provide useful tools and insights for managers to resolve what often appear as lose-lose situation between the persistence of species at risk and timber harvest in other forest ecosystems. These tools contribute to bridge the gap between conservation and forest management, two disciplines that remain too often disconnected in practice. © 2015 Elsevier Ltd.


Trottier-Picard A.,Center Detude Of La Foret Cef | Trottier-Picard A.,University of Québec | Thiffault E.,Natural Resources Canada | DesRochers A.,Center Detude Of La Foret Cef | And 7 more authors.
Forest Ecology and Management | Year: 2014

We quantified the effects of different loads of forest logging residues on the microenvironment (soil temperature, soil volumetric water content, competing vegetation cover, and available nutrients) of planted hybrid poplars one year after planting, and assessed the corresponding seedling growth until the third growing season. In four experimental plantations across Quebec (Canada), we used a factorial design of four residue loads that were applied at the tree-level over three planted species: hybrid poplars ( Populus spp.), black spruce ( Picea mariana (Mill.) BSP), and either jack pine ( Pinus banksiana Lamb.) or white spruce ( Picea glauca (Moench) Voss), depending upon the site. Logging residues linearly decreased competing vegetation cover on two of four sites and reduced fluctuations in soil temperature on all sites. Logging residues also decreased summer soil temperatures at all sites through a negative quadratic effect. On one site, the frequency of freeze-thaw cycles increased under logging residues, while logging residues increased soil water content on another site, for certain measurement events. Logging residues did not affect available nutrients. Seedlings showed no consistent growth response to logging residues for three years after planting, except for a beneficial effect of logging residues on hybrid poplar growth on one site. Because logging residues affected seedling microclimate and competing vegetation, their maintenance and on-site spatial arrangement on site could be used to manipulate the growing conditions for planted trees. © 2013 Elsevier B.V.


Thiffault N.,Direction de la Recherche Forestiere | Thiffault N.,Center Detude Of La Foret Cef | Titus B.D.,Natural Resources Canada | Moroni M.T.,Natural Resources Canada | Moroni M.T.,Forestry Tasmania
Forestry Chronicle | Year: 2010

Successful regeneration following harvesting or natural disturbance is a fundamental prerequisite for sustainable forest management. However, some regenerating stands have poor juvenile growth rates, which compromise sustainable management objectives. In particular, the presence of some ericaceous species that proliferate after forest disturbance, such as Kalmia angustifolia, can slow succession of boreal stands to the point that ecosystem retrogression is induced. We used data from a silvicultural field trial established in central Newfoundland to evaluate how various combinations of silvicultural treatments (trench scarification, herbicide application, fertilization at planting) influenced growth of three conifer species planted on a Kalmia-dominated cutover. Ground-level diameter (GLD), height, diameter at breast height (DBH), and percent Kalmia cover were assessed at the end of 15 growing seasons after planting. We detected several interactions between silvicultural treatments and planted conifer species. Globally, height and estimates of foliar biomass of all conifer species responded positively to scarification. Fifteen-year height in both scarified and unscarified treatments was in the order Picea mariana < Pinusbanksiana < Larix laricina. Black spruce and jack pine height increased when Kalmia was controlled with herbicide, but height of tamarack was not. The use of herbicide significantly increased 15-year GLD and volume index of all three conifer species, but only black spruce responded positively to fertilization at planting. Our results confirm that species-specific responses to silvicultural treatments are to be expected when managing Kalmia-dominated sites. Although chemical vegetation management has great silvicultural potential, our results suggest that mechanical site preparation can also be effective in promoting early conifer seedling growth that leads to rapid canopy closure. It is anticipated that canopy closure will lead to exclusion of Kalmia later in the rotation through natural successional pathways. Copyright © 2010 Canadian Institute Forestry / Insitut forestier du Canada.


Graham-Sauve L.,University of Quebec at Montréal | Graham-Sauve L.,Center Detude Of La Foret Cef | Work T.T.,University of Quebec at Montréal | Work T.T.,Center Detude Of La Foret Cef | And 4 more authors.
Forest Ecology and Management | Year: 2013

Partial cutting has been proposed as a means to better conserve biodiversity in managed forest landscapes. However, partial cutting encompasses many forms of silviculture; some with implicit goals of maintaining biodiversity such as multicohort harvesting or others which may specifically focus on regeneration of stands but may still provide some additional benefits for biodiversity such as shelterwood harvesting. Here we compared ground beetle assemblages of clear cuts, shelterwoods, multicohort harvested stands and uncut stands collected using pitfall traps both 2 and 3-years post-harvest. We hypothesized that partial cutting treatments would maintain assemblages that were more similar to uncut stands than to clear cuts. We further hypothesized that among partial cuts the multicohort harvested stands, with relatively high levels of retention (66%), would maintain beetle assemblages that were more similar to uncut stands than would shelterwoods, which had lower levels of retention (50%). We collected 6692 individuals, representing 42 species. Catch rates of beetles were similar among all harvested treatments (shelterwood, multicohort and clear cuts) and lower than uncut stands. Species richness and composition was similar between shelterwood and multicohort stands. Both partial cut treatments fell between clear cuts and uncut stands in terms of species richness and compositional similarity. Compositional differences between uncut stands and partial cut stands were defined primarily by reduced abundances of forest associated species such as Agonum retractum (LeConte), Synuchus impunctatus (Say) and four Pterostichus species within partial cuts. Within partial cuts, beetle assemblages differed between machine corridors with 0% retention and adjacent partial cut strips (50% retention) and uncut vegetation corridors (100%). We conclude that both shelterwoods and multicohort harvesting stands provide at least initially similar benefits for biodiversity compared to clear cutting although neither maintains assemblages consistent with those found in uncut stands. We expect that these similarities will end once trees are removed from shelterwoods. The reductions in abundances within partial cuts may extend the time necessary for individual populations to increase to pre-harvest levels in partial cuts. For land-managers, similar initial responses of beetle assemblages in multicohort and shelterwood harvests may permit some flexibility for conservation planning whereby final removal of seed trees within shelterwoods could be delayed depending on the status of recovering beetle populations. © 2013 The Authors.


Baral S.K.,Center Detude Of La Foret Cef | Baral S.K.,University of Quebec at Rimouski | Schneider R.,Center Detude Of La Foret Cef | Schneider R.,University of Quebec at Rimouski | And 4 more authors.
Canadian Journal of Forest Research | Year: 2013

The presence of wound (strain) initiated discoloured wood columns in the core of sugar maple (Acer saccharum Marshall) stems reduces the proportion of white-coloured wood and, thus, lowers its commercial value. This study aimed to assess the relationship between tree characteristics and the extent and proportion of discoloured wood in sugar maple tree stems. Using 109 trees from three different sites in southern Quebec, we found that the proportion of discoloured wood increased with decreasing sapwood volume and increasing tree age. Younger trees showed a significantly lower proportion of discoloured wood volume. Discoloured wood volume increases disproportionately with tree diameter, while varying among sites. The third important factor affecting the amount of discolored wood was tree vigour as measured by crown characteristics and growth rate changes. A nonlinear mixed-effects model was used to predict discoloured wood taper. Height along the stem was used as a predictor, along with diameter at 1.3m(DBH), the ratio of live crown length to tree height, and tree height. Although observed injury surface area was positively correlated to discoloured wood volume, injury information did not explain a large share of discoloured wood proportion variation. Overall, older and larger trees with many injuries on less productive sites are likely to have more discoloured wood.


Baral S.K.,Center Detude Of La Foret Cef | Baral S.K.,University of Quebec at Rimouski | Baral S.K.,University of Moncton | Berninger F.,Center Detude Of La Foret Cef | And 5 more authors.
Trees - Structure and Function | Year: 2016

Key message: Discoloured heartwood proportion (DHP) decreases with an increasing rate of heartwood formation for vigorous sugar maple trees, suggesting that age-related increase in DHP is due to increasing likelihood of injuries with tree age.Abstract: Sugar maple heartwood is more susceptible to decay and discolouration than the sapwood. To understand heartwood formation, foliage, sapwood, heartwood, and discoloured wood areas as well as other biometric variables were measured on 79 trees sampled in two sites in south-eastern Quebec, Canada. Tree growth was related to heartwood formation and discolouration with a modelling approach. Heartwood formation increased with tree height, age, and crown size, but decreased with increasing leaf area to stem basal area ratio. In general, the proportion of discoloured heartwood increased with an increasing rate of heartwood formation. However, for trees visually classified as vigorous, the proportion of discoloured heartwood tended to decline with an increasing rate of heartwood formation. This indicates that the size/age-related increase in discoloured wood proportion in sugar maple is possibly due to older trees being more likely to have injuries and inoculations by fungi. Thus, residual stands composed of high vigour trees can likely maintain higher growth while minimizing discoloured wood proportion. © 2016 Springer-Verlag Berlin Heidelberg


In Québec (Canada), large planting stock are used for reforestation of high-competition sites, sometimes in combination with soil scarification. Large conifer seedlings are typically produced in containers >300 cm3, or as bare-root stock. Nursery practices are expected to influence seedling mechanical stability. We measured large containerized and bare-root black spruce (Picea mariana) seedling stability (resistance to winching), and characterized their root architecture, during their seventh growing season since planting in scarified or non-scarified plots devoid of any competing vegetation. We detected no significant stock type or scarification effect on seedling height, diameter, height/diameter ratio, stability, total number of roots and adventive roots. Occurrences of root deformations, as well as vertical and horizontal root distributions, were not influenced significantly by the treatments. The height/diameter ratio was the sole significant predictor of the resistance to winching. Our results indicate that the use of either large containerized or large bare-root stock has limited silvicultural consequences. In this context, the choice of large stock type should be based on other factors, such as handling constraints.

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