Philippe Nolet

Relationship between canopy disturbance history and current sapling density of Fagus grandifolia and Acer saccharum in a northern hardwood landscape

To shed light on the currently increasing proportion of Fagus grandifolia Ehrh. saplings in the tolerant hardwood forests of Quebec, we studied 48 Acer saccharum Marsh. dominated stands with contrasting histories of canopy disturbance: old commercial clear-cutting (CC), old fire (F), and either one or two partial cuts (1PC and 2PC). Our results indicated that higher densities of both F. grandifolia and A. saccharum saplings were associated with partial cutting histories (1PC and 2PC) than with severe canopy disturbance (CC and F). The density of F. grandifolia saplings was not related to any soil or stand characteristics in stands with a history of severe canopy disturbance. However, in stands with a history of partial canopy disturbances, the relative density of F. grandifolia saplings as compared with A. saccharum was related to soil C/N ratio and the presence of F. grandifolia overstory trees, whereas the absolute density showed a negative relationship with stand basal area. Therefore, it appears that ...

The successional status of sugar maple (Acer saccharum), revisited

Two complementary experimental designs at two contrasting scales (landscape/long term; individual tree/short term) were used for an in-depth evaluation of the successional status of sugar maple (AS: Acer saccharum Marsh.). First, forest disturbances during the 20th century and composition were mapped for two landscapes in the Du Lièvre watershed of southern Quebec. Our results show that, as well as dominating stands in the absence of fire, AS often rapidly developed dominance after fire, especially in the south of our study area. Similarly, a majority of AS-dominated stands clearcut in 1928 continued to be AS-dominated 60 years later. Second, we examined AS seedlings planted under two very contrasting light regimes. AS seedlings showed a combination of traits particularly adapted to tolerate shade under a low light regime. However, owing to a surprisingly high phenotypic plasticity, AS also exhibited efficient development under high light. This suggests the classification of AS as a late-successional species should indeed be revised and that generalist or trans-successional would be a more appropriate designation for this species. We discuss the ramifications of such a status revision, with an emphasis on the implications for its silviculture.RésuméDeux dispositifs expérimentaux complémentaires, établis à deux échelles différentes (paysage/long terme et individu/court terme), ont été utilisés afin de mieux évaluer le statut successionnel de l’érable à sucre (AS : Acer saccharum Marsh.). D’abord, une cartographie des perturbations et de la composition forestière au cours du 20e siècle a été réalisée pour deux paysages du bassin du Lièvre dans le Sud du Québec. Nos résultats ont démontré qu’en plus de dominer les peuplements en absence de perturbation du couvert, AS établissait souvent et rapidement une dominance dans les peuplements ayant brûlé, et cela, particulièrement dans le paysage le plus au sud de l’air d’étude. De la même façon, une majorité de peuplements dominés par AS et coupés à blanc en 1928 s’est révélée encore dominée par AS à peine 60 ans après coupe. Ensuite, en réalisant le suivi de semis plantés sous deux régimes lumineux très différents, AS a montré un ensemble de caractéristiques particulièrement adaptées à une bonne tolérance à l’ombre. Cependant, grâce à une étonnante plasticité phénotypique, AS a aussi démontré un développement compétitif sous des régimes lumineux plus élevés. L’ensemble de ces résultats suggère donc une remise en question du statut de fin de succession de AS, lequel répondrait mieux à une appellation d’espèce généraliste ou trans-successionnelle. Les implications d’une telle révision sur la sylviculture de cette essence sont discutées.

Potentials and limitations of ecological classification as a tool for forest management: a case study of disturbed deciduous forests in Québec

Abstract The forest ecosystems of the most southern part of Quebec have been influenced by activities of various intensities and spatial distribution (harvesting, agriculture, pastureland, etc.) since the beginning of settlement. These activities have changed the natural relationships between soil and vegetation characteristics. The aims of this study were (1) to identify, with a concrete example, the difficulties encountered by a forest ecological classification program in disturbed deciduous forests and (2) to evaluate the efficacy, for forest managers, of the products derived from that classification. We first show, by a complete linkage cluster analysis, that the forest type concept is not appropriate for the disturbed deciduous forests context because of the great variability in forest composition and the low relationships between soil and vegetation. By comparing information required to manage effectively the disturbed deciduous forest to the information provided by the Quebec Forest Ecological Classification Program (FECP), we demonstrate, in the second part of the study, some shortcomings of this program at the site scale. Three main reasons are given to explain the weaknesses encountered. The first one is that the disturbed characteristics of these forests increase the complexity of forest and ecological mapping. The second main reason is that some vegetation and soil characteristics are so variable that it is almost impossible to predict them with ecological classification. Deficiencies in the methodology used in the Quebec FECP constitute the third main reason explaining the weaknesses encountered. From these results, we propose some solutions to enhance the support that the Quebec FECP can bring to forest managers in disturbed deciduous forests. Finally, shortcomings of ecological classification at the site scale do not necessarily limit its potential at the regional scale.

Comparing the effects of even- and uneven-aged silviculture on ecological diversity and processes: A review

Abstract With an increasing pressure on forested landscapes, conservation areas may fail to maintain biodiversity if they are not supported by the surrounding managed forest matrix. Worldwide, forests are managed by one of two broad approaches—even‐ and uneven‐aged silviculture. In recent decades, there has been rising public pressure against the systematic use of even‐aged silviculture (especially clear‐cutting) because of its perceived negative esthetic and ecological impacts. This led to an increased interest for uneven‐aged silviculture. However, to date, there has been no worldwide ecological comparison of the two approaches, based on multiple indicators. Overall, for the 99 combinations of properties or processes verified (one study may have evaluated more than one property or process), we found nineteen (23) combinations that clearly showed uneven‐aged silviculture improved the evaluated metrics compared to even‐aged silviculture, eleven (16) combinations that showed the opposite, and 60 combinations that were equivocal. Furthermore, many studies were based on a limited study design without either a timescale (44 of the 76) or spatial (54 of the 76) scale consideration. Current views that uneven‐aged silviculture is better suited than even‐aged silviculture for maintaining ecological diversity and processes are not substantiated by our analyses. Our review, by studying a large range of indicators and many different taxonomic groups, also clearly demonstrates that no single approach can be relied on and that both approaches are needed to ensure a greater number of positive impacts. Moreover, the review clearly highlights the importance of maintaining protected areas as some taxonomic groups were found to be negatively affected no matter the management approach used. Finally, our review points to a lack of knowledge for determining the use of even‐ or uneven‐aged silviculture in terms of both their respective proportion in the landscape and their spatial agency.

Early-stage of invasion by beech bark disease does not necessarily trigger American beech root sucker establishment in hardwood stands

Two concomitant phenomena currently affect the dynamics of sugar maple-American beech (AB) stands in northeastern North America: beech bark disease (BBD), and increased AB understory density. Many studies suggest a causal link between the two phenomena, i.e., BBD favouring beech regeneration. But this link has yet to be experimentally demonstrated. To address the question, we compared regeneration composition between recently BBD-affected and -unaffected stands. A total of 109 stands were sampled; half were affected by BBD. Seedling and sapling density were assessed, together with the origin (seedling or sprout). While BBD affects stands in the eastern part of the study region, AB was observed in the understory across the entire region. No clear difference in AB sprout density between BBD-affected and -unaffected stands was observed while AB seedling density—as well as pooled AB seedling and sprout density were higher in unaffected stands. Findings suggests that BBD, in its early stage, is not a necessary trigger of AB understory establishment. Yet, AB sapling basal area generally was higher in stands affected by BBD, likely indicating a greater rate of AB understory development due to increased light availability beneath a more open crown canopy. That development can lead to AB understory dominance. This distinction—BBD not necessarily triggering AB root sucker establishment but favoring AB advance regeneration development—also questions the generalized perception that dense AB thickets necessarily originate from root suckers.