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Featured researches published by Marilou Beaudet.


Forest Ecology and Management | 2003

Use of a spatially explicit individual-tree model (SORTIE/BC) to explore the implications of patchiness in structurally complex forests

K. David Coates; Charles D. Canham; Marilou Beaudet; Donald L. Sachs; Christian Messier

The discipline of silviculture is evolving rapidly, moving from an agricultural model that emphasized simple stand structures toward a natural disturbance- or ecosystem-based model where stands are managed for multiple species and complex structures. Predicting stand dynamics and future yields in mixed-species complex structured stands cannot be easily accomplished with traditional field experiments. We outline the development and structure of SORTIE/BC, a descendent of the SORTIE model. SORTIE/BC is a light-mediated, spatially explicit, mixed-species forest model that makes population dynamic forecasts for juvenile and adult trees. We use the model to simulate partial cutting prescriptions in temperate deciduous, boreal and temperate coniferous mixed-species forests. The species, amount and spatial pattern of canopy tree removal had a major influence on understory light environments. Low and uniform removal of canopy trees were less successful in favouring the growth and survival of regenerating trees of intermediate to shade intolerant species and the growth of retained canopy trees than patch removal. In the boreal mixedwood, strip-cutting can maintain mixed stands but careful attention must be paid to buffer and strip management to optimize stand growth. We conclude that SORTIE/ BC can be very useful to explore and explain the silvicultural implications of complex silvicultural prescriptions for which there are no existing long-term experiments.


Agricultural and Forest Meteorology | 2002

Variation in canopy openness and light transmission following selection cutting in northern hardwood stands: an assessment based on hemispherical photographs

Marilou Beaudet; Christian Messier

The objective of this study was to determine how canopy openness (CO) and light transmission are affected by selection cutting, and how they vary over time following harvesting in northern hardwood stands. We sampled five sugar maple—yellow birch—beech (Acer saccharum—Betula alleghaniensis—Fagus grandifolia) stands in Quebec (Canada). The stands had been logged, using the selection system, at different times (2–14 years) before the study, and were used as a chronosequence. We also sampled portions of each stand which had been kept as uncut controls. Ten 1 ha plots were sampled (five cuts and five paired controls). We took 20 hemispherical photographs per plot, at 5 m above-ground, which was above most understory vegetation. The CO, light transmission (gap light index (GLI) sensu Canham (1988)), sunflecks characteristics, and angular distribution of openings from the zenith were calculated for each photograph. Selection cutting increased CO, especially within 60 ◦ of the zenith. The greater CO in the cuts allowed a greater light transmission (GLI), longer sunflecks, and a longer cumulative daily sunflecks duration (CDSD). The differences observed between the cuts and the control plots in terms of CO, GLI, and CDSD were greatest in the more recent cuts, and decreased as a function of time since logging. The relationships were best described by negative logarithmic (CO) and negative exponential (GLI, CDSD) models. In the youngest cut (2 years old), the CO, GLI, and CDSD were on average 2.3–2.5 times higher than in the control, while in the oldest cut (14 years old), the same variables were 1.6–1.7 times higher than in the control. The results of this study emphasize the importance of taking into account the temporal variation in canopy openness and light transmission after canopy disturbances such as selection cutting because that variation will likely have an important influence on regeneration dynamics.


Forest Ecology and Management | 2002

Predictions of understorey light conditions in northern hardwood forests following parameterization, sensitivity analysis, and tests of the SORTIE light model

Marilou Beaudet; Christian Messier; Charles D. Canham

We parameterized the light model of SORTIE for northern hardwoods in eastern Canada, and performed a sensitivity analysis and validation tests of the model before using it to predict the effect of various types of partial cutting on understorey light conditions. The parameterization was done by characterizing the crown geometry and openness of sugar maple (Acer saccharum Marsh.), yellow birch (Betula alleghaniensis Britt.), and beech (Fagus grandifolia Ehrh.). Those results indicated that beech casts a deeper shade than sugar maple and yellow birch. The sensitivity analysis showed that the model predictions were more sensitive to variations in the crown geometry parameters, especially the crown radius parameter, than to variations in crown openness. Validation tests of the model were performed in both mapped and unmapped plots by comparing light predicted by SORTIE to light measured in the field using hemispherical photographs and sensor-based measurements. In mapped stands, the model provided reasonably accurate predictions of the overall variation in understorey light levels between 2 and 30% full sunlight, but the predictions tended to lack spatial precision. In unmapped stands, SORTIE accurately predicted stand-level mean light availability at 5 m aboveground for stands ranging in basal area from 19 to 27 m2/ha. At heights lower than 5 m, SORTIE accurately predicted the light availability in a recent selection cut with a low density of understorey vegetation, but tended to overestimate light availability in stands with relatively dense undergrowth. Finally, a demonstration of the possible usefulness of the SORTIE light model is presented by using the model to compare the proportion of various light microsites created by a variety of selection cutting systems in use in eastern Canada (selection cutting with different harvesting intensities, group selection, and patch selection).


Ecoscience | 1999

Possible mechanisms of sugar maple regeneration failure and replacement by beech in the Boisé-des-Muir old-growth forest, Québec

Marilou Beaudet; Christian Messier; David Paré; Jacques Brisson; Yves Bergeron

AbstractTo better understand the causes of sugar maple (Acer saccharum Marsh.) replacement by beech (Fagus grandifolia Ehrh.) in the Boise-des-Muir old-growth forest (Quebec), we studied, i) the ef...


Archive | 2009

Functional Relationships Between Old-Growth Forest Canopies, Understorey Light and Vegetation Dynamics

Christian Messier; Juan M. Posada; Isabelle Aubin; Marilou Beaudet

The distinct structural and compositional features, understorey light conditions and understorey vegetation of old-growth forests in boreal, temperate and tropical biomes are discussed. Old-growth forests are characterised by gap dynamics that create a structurally complex and dynamic vertical and horizontal crown and understorey light environment. In both temperate and tropical forests, gaps tend to close quickly from both regrowth of lateral crown and understorey vegetation. In boreal forests, gaps tend to last longer and fill mainly from understorey vegetation. Understorey light is generally below 5% near the forest floor in all biomes, with very few microsites having high light levels. Above the main understorey vegetation, however, light is more variable and can reach up to 65% in some old-growth boreal forests. This heterogeneous, complex and unpredictable understorey light environment acts as a selective filter that promotes unique understorey plant adaptations.


Archive | 1999

SORTIE: a resource mediated, spatially-explicit and individual-tree model that simulates stand dynamics in both natural and managed forest ecosystems

Christian Messier; K. Coates; Marilou Beaudet; Charles D. Canham; Donald L. Sachs

SORTIE was originally developed in the early 1990s for mixed deciduous forests in eastern North America. One of the major distinctive features of SORTIE, compared to the JABOWA-FORET family of gap models, is that the model structure originated from field experiments and heavily relies on the input of data from field studies. During the past four years, the model has been extensively modified for the temperate mixed-species forests of northwestern British Columbia (SORTIE/BC). Significant changes were made to the original SORTIE model to take into account unique features of western forests and unique challenges posed by use of the model for management planning. Currently, work is underway to use SORTIE for southern hardwood forests in Quebec, boreal mixedwood and black spruce forests of Canada, temperate forests of New Zealand and tropical forests of Puerto Rico. The SORTIE model consists of a mixture of mechanistically and empirically-derived relationships (i.e. hybrid model) and is comprised of four basic submodels: (1) seedling recruitment – a function of parent tree proximity and seedbed substrate; (2) resource availability – predicts understory light dynamics as a function of species specific light extinction coefficients; (3) subcanopy tree growth – function of light availability and previous growth history and; (4) tree mortality – function of recent growth rates. We are currently working to add an understory vegetation submodel and to improve our prediction of growth and mortality of mature canopy trees. The model is ideal for examining stand dynamic and succession after smallto intermediate-scale disturbance in structurally complex mixed or single-species stands. From a forest management perspective, the model has a very flexible user-interface to allow incorporation of a wide range of partial cutting strategies (e.g., understory protection, diameter limit, shelterwood, variable retention). The model easily simulates prescriptions that retain complex stand structures, especially the influence of retained canopy trees on recruitment, growth and mortality of sub-canopy trees. Current model predictions include: (1) spatial distribution and sizes of all individuals in a simulated stand; (2) DBH and height distributions by species; (3) changes in basal area and density, by species, over time; (4) tables of basal area and densities of both adult and juvenile trees and; (5) distribution of subcanopy light levels. Three examples are provided that demonstrate the ecological and silvicultural questions that can be addressed by SORTIE in both the temperate and boreal forests of North America. We are currently re-engineering the model in order to facilitate and improve the continuously changing requirements of the SORTIE users and developers.


Ecology Letters | 2006

Reconciling niche and neutrality: the continuum hypothesis

Dominique Gravel; Charles D. Canham; Marilou Beaudet; Christian Messier


Canadian Journal of Forest Research | 1998

Growth and morphological responses of yellow birch, sugar maple, and beech seedlings growing under a natural light gradient

Marilou Beaudet; Christian Messier


Forest Ecology and Management | 2005

Comparing composition and structure in old-growth and harvested (selection and diameter-limit cuts) northern hardwood stands in Quebec

Viriginie Arielle Angers; Christian Messier; Marilou Beaudet; Alain Leduc


Canadian Journal of Forest Research | 2000

Light extinction coefficients specific to the understory vegetation of the southern boreal forest, Quebec

Isabelle Aubin; Marilou Beaudet; Christian Messier

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Christian Messier

Université du Québec à Montréal

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Alain Leduc

Université du Québec à Montréal

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Brian D. Harvey

Université du Québec en Abitibi-Témiscamingue

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Daniel Kneeshaw

Université du Québec à Montréal

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Yves Bergeron

Université du Québec en Abitibi-Témiscamingue

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K. David Coates

United States Forest Service

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Isabelle Aubin

Natural Resources Canada

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