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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. [ABSTRACT FROM AUTHOR]

Sugar maple (SM, Acer saccharum Marsh.) dominated forests of North America are increasingly affected by many human-induced modifications in environmental conditions. As a remedy, adapted silvicultural treatments are needed. Even though it is generally accepted that SM health is related to soil fertility and even though there is extensive literature on SM - American beech (AB, Fagus grandifolia Ehrh.) regeneration stand dynamics related to light availability, the interaction between these two factors has rarely been studied. Our main objective was thus to verify the possible role of a light-soil interaction on SM-AB stand dynamics. We used a factorial design with three factors (harvest intensity, liming, and AB sapling elimination) to test this interaction. Our results showed that the radial growth of SM and AB tree and sapling growth was positively affected by canopy opening but not by liming. Liming did not favour AB seedlings, whereas it favoured SM seedlings in specific canopy opening situations, confirming, albeit partially, the light-soil interaction hypothesis. Overall, liming had very limited effects on SM-AB stand dynamics compared with canopy opening and AB sapling elimination treatments. We do not advocate the extensive use of liming, as other silvicultural strategies tested provided more promising results to favour SM over AB. [ABSTRACT FROM AUTHOR]

Control of competing vegetation is recommended to ensure successful Yellow birch ( Betula alleghaniensis Britton) regeneration within juvenile stands that do not sustain high enough sapling densities of this species. Four contrasting vegetation control treatments were tested to determine their effect on the growth and vigor of eight-year-old B. alleghaniensis saplings regenerating after final cutting of a shelterwood seed cut. Vegetation control treatments were TC (total circular removal), PC (circular removal of codominant competing vegetation), TS (total semicircular removal on 180° section), and NC (no vegetation control). Two years after treatment application, diameter growth significantly improved in response to vegetation control treatments, whereas sapling height growth did not. This pattern of biomass allocation was directly related to sapling etiolation, which increased with decreasing severity of vegetation removal. As a result, application of vegetation control, especially TC and PC treatments, was valuable in reducing signs of stress in saplings. However, increasing the severity of vegetation removal also made saplings more conspicuous to herbivores, which increased browsing, especially in the TC and PC treatments. Browsing was sufficient in some plots of the TC and PC treatments to overcome the vigor and diameter growth enhancements observed when browsing was negligible. In contrast to the TC and PC treatments, the TS treatment kept browsing very low while largely removing competition. The results suggest that B. alleghaniensis saplings established after final cutting of a shelterwood seed cut do take advantage of vegetation control treatments, but the decision to apply these treatments must include consideration of local herbivore population densities. [ABSTRACT FROM AUTHOR]

Process-based forest growth models with spatially explicit representation are relevant tools to investigate innovative silviculture practices and/or climate change effects because they are based on key ecophysiological processes and account for the effects of local competition for resources on tree growth. Such models are rare and are often calibrated for a very limited number of species and rarely for mixed and/or uneven-aged stands, and none are suitable for the temperate forests of Québec. The aim of this study was to calibrate and evaluate HETEROFOR (HETEROgeneous FORest), a process-based and spatially explicit model based on resource sharing, for 23 functionally diverse tree species in forest stands with contrasting species compositions and environmental conditions in southern Quebec. Using data from the forest inventory of Quebec, we evaluated the ability of HETEROFOR to predict the short-term growth (5–16 years) of these species at the tree and stand levels and the long-term dynamics (120 years) of red and sugar maple stands. The comparison between the prediction quality of the calibration and evaluation datasets showed the robustness of the model performance in predicting individual-tree growth. The model reproduced correctly the individual basal area increment (BAI) of the validation dataset, with a mean Pearson's correlation coefficient of 0.56 and a mean bias of 18 %. Our results also highlighted that considering tree position is of importance for predicting individual-tree growth most accurately in complex stands with both vertically and horizontally heterogeneous structures. The model also showed a good ability to reproduce BAI at the stand level, both for monospecific (bias of - 3.7 %; Pearson's r=0.55) and multi-species stands (bias of - 9.1 %; Pearson's r=0.62). Long-term simulations of red maple and sugar maple showed that HETEROFOR was able to accurately predict the growth (basal area and height) and mortality processes from the seedling stage to the mature stand. Our results suggest that HETEROFOR is a reliable option to simulate forest growth in southern Quebec and to test new forestry practices under future climate scenarios. [ABSTRACT FROM AUTHOR]

Process-based forest growth models with spatially explicit representation are a relevant tool to investigate innovative silviculture practices and/or climate change effects because they are based on key ecophysiological processes and account for the effects of local competition for resources on tree growth. Such models are rare, often calibrated for a very limited number of species and rarely in mixed and/or uneven-aged stands, and none are suitable for the temperate forests of Québec. The aim of this study was to calibrate and evaluate HETEROFOR, a process-based and spatially explicit model based on resource sharing, for 23 functionally diverse tree species in forest stands with contrasting species compositions and environmental conditions in southern Québec. Using data from the forest inventory of Québec, we evaluated the ability of HETEROFOR to predict the short-term growth (5-16 years) of these species at the tree and stand levels, and the long-term dynamics (120 years) of red and sugar maple stands. The comparison between the prediction quality for the calibration and evaluation datasets showed the robustness of the model performance in predicting individual tree growth. The model reproduced correctly individual basal area increment (BAI) of the validation dataset with a mean Pearson’s correlation coefficient of 0.56 and a mean bias of 18%. Our results also highlighted that considering tree position is of importance for predicting individual tree growth most accurately in complex stands with both vertical and horizontal heterogeneous structure. The model also showed a good ability to reproduce BAI at the stand level, both for monospecific (bias of -3.7%, Pearson’s r = 0.55) and multi-species stands (bias of -9.1%, Pearson’s r = 0.62). Long-term simulations of red maple and sugar maple showed that HETEROFOR was able to accurately predict the growth (basal area and height) and mortality processes from the seedling stage to the mature stand. Our results suggest that HETEROFOR is a reliable option to simulate forest growth in southern Québec and test new forestry practices under future climate scenarios. [ABSTRACT FROM AUTHOR]

The area of forest plantations is increasing worldwide helping to meet timber demand and protect natural forests. However, with global change, monospecific plantations are increasingly vulnerable to abiotic and biotic disturbances. As an adaption measure we need to move to plantations that are more diverse in genotypes, species, and structure, with a design underpinned by science. TreeDivNet, a global network of tree diversity experiments, responds to this need by assessing the advantages and disadvantages of mixed species plantations. The network currently consists of 18 experiments, distributed over 36 sites and five ecoregions. With plantations 1-15 years old, TreeDivNet can already provide relevant data for forest policy and management. In this paper, we highlight some early results on the carbon sequestration and pest resistance potential of more diverse plantations. Finally, suggestions are made for new, innovative experiments in understudied regions to complement the existing network. [ABSTRACT FROM AUTHOR]

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 partial canopy disturbances favored the regeneration of F. grandifolia relative to A. saccharum, whereas severe canopy disturbances may have provided an advantage to A. saccharum. We suggest that the presence of a light threshold can explain this shift in sapling performance between these two species. Pour tenter d’élucider l’augmentation de la proportion de gaule de Fagus grandifolia Ehrh. observée dans les forêts de feuillus tolérants à l’ombre du Québec, nous avons étudié 48 peuplements dominés par Acer saccharum Marsh. Ces peuplements se distinguent par leur historique de perturbation de la canopée : vieille coupe à blanc commerciale (CC), vieux feu (F) et une ou deux coupes partielles (1CP et 2CP). Nos résultats indiquent que les fortes densités de gaules de F. grandifolia et d’A. saccharum étaient davantage associées à un historique de coupe partielle (1CP et 2CP) qu’à des perturbations plus sévères de la canopée (CC et F). La densité des gaules de F. grandifolia n’était reliée à aucune caractéristique du sol ou du peuplement dans les peuplements ayant un historique de perturbation sévère de la canopée. Cependant, dans les peuplements ayant un historique de coupe partielle, la densité relative des gaules de F. grandifolia par rapport à celles d’A. saccharum était reliée au rapport C/N et à la présence de tiges de F. grandifolia dans l’étage dominant, alors que la densité absolue était négativement reliée à la surface terrière du peuplement. Il semble donc que des perturbations partielles de la canopée favorisent la régénération de F. grandifolia par rapport à celle d’A. saccharum, alors que les perturbations sévères de la canopée procureraient un avantage à A. saccharum. Nous croyons qu’il existe un seuil de luminosité pouvant expliquer les différences de densité des gaules de ces deux espèces. [ABSTRACT FROM AUTHOR]