Red alder is a common component of low elevation CWH zone forests in Southwestern BC and often gr... more Red alder is a common component of low elevation CWH zone forests in Southwestern BC and often grows intimately with young conifer stands on highly productive sites. It is a strong competitor in young conifer stands and rapidly overtops juvenile conifers, often making it challenging to meet free growing obligations under current standards. Presently, many forest managers err on the side of caution and expend resources to control red alder to meet free growing requirements. Unfortunately, we are unable to determine whether these expenditures are warranted due to a lack of scientific data. This project provides preliminary best available information to assist in improving policies and practices around free-growing. This project utilises mixed alder-conifer experiments that were designed to study the competitive effects of red alder on conifers. The experimental sites are now old enough to assess the 11-yr free growing window. During the first year of this project (2004/2005) standard ...
Self-thinning or density-induced mortality is the consequence of competition between individuals ... more Self-thinning or density-induced mortality is the consequence of competition between individuals of a stand and takes place when resources for tree development become insufficient for individuals needs or for the stand as a whole. Since density by itself is not a good indicator of competition between component species, other expressions -like Reineke’s stand density index (SDI) - have been proposed as suitable indicators of site occupancy and competition. Specific objectives of this research are: a) to develop density - size relationships and relative density indexes for aspen and white spruce mixtures and, b) to investigate the effect of composition and site quality on maximum density - size relationships and stand growth rates. We are using data from permanent sample plots for trembling aspen ñ white spruce stands from western Canada (Alberta, Saskatchewan and Manitoba) to examine the usefulness of density - size relationships in mixed and pure stands of these species. Modeling of...
Establishing white spruce (Picea glauca (Moench) Voss) by planting it under established aspen (Po... more Establishing white spruce (Picea glauca (Moench) Voss) by planting it under established aspen (Populus tremuloides Michx.), stands has substantial potential as a technique for regenerating boreal mixedwood stands. The presence of an aspen overstory serves to ameliorate frost and winter injury problems and suppresses understory vegetation that may compete with white spruce. In this study we examine the growth of white spruce during the first 10 years after being planted underneath a 39-year-old stand of trembling aspen following thinning and fertilization. Results indicate successful establishment and reasonable growth rates of white spruce planted under thinned and unthinned aspen stands, even with aspen basal area of 51 m2 ha−1. Thinning of overstory aspen to 1000 or 2000 stems ha−1 did not increase light reaching seedlings, but did result in improvements in light above the shrub layer and in diameter and height growth of the underplanted seedlings. However, these increases in growth of underplanted spruce may not justify the expense of thinnings. Fertilization of these stands prior to planting had no effect on spruce growth. Growth of spruce underplanted at this site near Fort Nelson was similar to that at two other stands near Dawson Creek, B.C.Information on treatment effects on light, beam fraction, air temperature, and soil temperature are presented. Measurements of light obtained using LAI-2000 and hemispherical photography were compared with those obtained from hourly PPFD measurements. Results indicate that while both methods provide estimates of transmittance that are highly correlated with those provided by actual light measurements, they provide substantial underestimates of actual light levels.
While aspen (Populus tremuloides Michx.) cover provides protection from growing season radiative ... more While aspen (Populus tremuloides Michx.) cover provides protection from growing season radiative frosts, reduced light levels can limit growth of understory white spruce (Picea glauca (Moench) Voss). The creation of openings around individual spruce can provide more light, but the chance of radiative frost damage increases as gaps become larger. We examined the relationship between opening size and light and
On productive sites, young paper birch (Betula papyrifera Marsh.) outgrows most of the conifers w... more On productive sites, young paper birch (Betula papyrifera Marsh.) outgrows most of the conifers with which it is associated. Due to its dominant position in the canopy, and the potentially high densities of birch regeneration found on some sites, its presence may lead to a reduction in the amount of light reaching subordinate conifers. To evaluate the potential use of
Preliminary results indicate that patterns of tree growth are related to microclimatic gradients ... more Preliminary results indicate that patterns of tree growth are related to microclimatic gradients in these openings. Height growth of the various tree species reflects their tolerance to drought and shade in openings. Among the tree species evaluated, Western hemlock and Engelmann spruce were best suited at the south edge and in the intact forest, but Douglas fir performed best at
Plant size often influences shade tolerance but relatively few studies have considered the functi... more Plant size often influences shade tolerance but relatively few studies have considered the functional response of taller plants to contrasting light environments. Several boreal and sub-boreal Abies, Picea and Pinus species were studied along a light (0-90% full sunlight) and size (30-400-cm high) gradient to examine the interactive influence of tree size and light availability on aboveground biomass distribution. Sampling was conducted in two regions of Canada: (A) British Columbia, for Abies lasiocarpa (Hook.) Nutt., the Picea glauca (Moench.) Voss x P. engelmannii Parry ex. Engelm. complex and Pinus contorta Dougl. var. latifolia Engelm.; and (B) Quebec, for Abies balsamea (L.) Mill., Picea glauca (Moench. Voss) and Pinus banksiana (Lamb.). All biomass distribution traits investigated varied with size, and most showed a significant interaction with both size and light, which resulted in increasing divergences among light classes as size increased. For example, the proportion of needle mass decreased as size increased but the rate of decrease was much greater in saplings growing at below 10% full sunlight. Needle area ratio (total needle area:aboveground mass) followed a similar pattern, but decreased more rapidly with increasing tree size for small trees up to 1 m tall. The proportion of needle biomass (needle mass ratio) was always lower in taller trees (i.e., > 1 m tall) than in small trees (< 1 m tall) and increasingly so at the lowest solar irradiances (0-10% full sunlight). Thus, extrapolating the functional response to light from small seedling to taller individuals is not always appropriate.
Canadian Journal of Forest Research-revue Canadienne De Recherche Forestiere, 2003
Five years after spacing a young, 11 m tall paper birch (Betula papyrifera Marsh.) stand, we exam... more Five years after spacing a young, 11 m tall paper birch (Betula papyrifera Marsh.) stand, we examine rela- tionships between growth of understory white spruce (Picea glauca (Moench) Voss), subalpine fir (Abies lasiocarpa (Hook.) Nutt.), and level of birch retention. Our objectives were to evaluate the effectiveness of selected measures of competition for estimating the effects of the residual birch
ABSTRACT The effectiveness of competition indices for predicting light transmittance and white sp... more ABSTRACT The effectiveness of competition indices for predicting light transmittance and white spruce (Picea glauca (Moench) Voss) growth were examined across trembling aspen (Populus tremuloides Michx.) density gradients using sites from a long-term study of mixedwood growth and development in Alberta and Saskatchewan. Competition indices based on density (number of trees, basal area, and spacing factor), distance-dependent and -independent size ratio (Hegyi's and Lorimer's), and crown characteristics (crown volume, surface area, and cross-sectional area) were tested. Transmittance was effectively predicted by crown competition indices followed closely by aspen basal area and size ratio indices. Models of spruce growth indicated better results for stem volume compared with diameter or height. Competition alone accounted for less than 60% of stem growth variation, with basal area and transmittance providing some of the best models. The predictive ability of spruce growth was increased up to 93% by adding initial size as a second explanatory variable. In this respect, initial diameter was superior to initial height, crown volume, and surface area. Relationships between competition, transmittance, and spruce growth were found to differ significantly between geographical locations. These results suggest the need for local development of models relating tree growth to competition.
The influence of aspen ( Populus tremuloides Michx.) and herbaceous (forb and grass) vegetation o... more The influence of aspen ( Populus tremuloides Michx.) and herbaceous (forb and grass) vegetation on resource availability and white spruce ( Picea glauca (Moench) Voss) growth were examined as part of a long-term experiment established in 2002 near Whitecourt, Alberta, Canada. ...
ABSTRACT Vertical and horizontal patterns of light within gaps and expansion of trees into gaps w... more ABSTRACT Vertical and horizontal patterns of light within gaps and expansion of trees into gaps were examined in young stands dominated by trembling aspen (Populus tremuloides Michx.) in northeastern British Columbia and northwestern Alberta. Lateral growth of branches of aspen edge trees averaged 15.2 cm/year and was similar to crown expansion rates reported for edge trees in eastern North America. Branches growing into gaps were significantly longer than those growing away from gaps and are likely to lead to gap shrinkage and reductions in light within gaps. However, height growth of edge trees was not significantly different from that of trees within the surrounding stands. Models describing relationships between diffuse transmittance and locations within gaps and surrounding stand height were developed in this paper. Sky view angle (SVA) was found to be effective for predicting transmittance to different locations within gaps. When SVA values exceed 1.2 (at the B.C. sites), white spruce (Picea glauca (Moench) Voss) will receive <40% of full sunlight, which is less than optimal for spruce height growth.
Effectiveutilization of a patch or cluster approach to growing aspen-white spruce mixtures in the... more Effectiveutilization of a patch or cluster approach to growing aspen-white spruce mixtures in the boreal forest requires an understanding of how the faster growing aspen patches influence microclimate and spruce growth in adjacent spruce patches. In this paper we examine, how young (11- 13 year old) aspen (Populus tremuloides Michx) patches influence microclimatic conditions in adjacent openings and how these
Red alder is a common component of low elevation CWH zone forests in Southwestern BC and often gr... more Red alder is a common component of low elevation CWH zone forests in Southwestern BC and often grows intimately with young conifer stands on highly productive sites. It is a strong competitor in young conifer stands and rapidly overtops juvenile conifers, often making it challenging to meet free growing obligations under current standards. Presently, many forest managers err on the side of caution and expend resources to control red alder to meet free growing requirements. Unfortunately, we are unable to determine whether these expenditures are warranted due to a lack of scientific data. This project provides preliminary best available information to assist in improving policies and practices around free-growing. This project utilises mixed alder-conifer experiments that were designed to study the competitive effects of red alder on conifers. The experimental sites are now old enough to assess the 11-yr free growing window. During the first year of this project (2004/2005) standard ...
Self-thinning or density-induced mortality is the consequence of competition between individuals ... more Self-thinning or density-induced mortality is the consequence of competition between individuals of a stand and takes place when resources for tree development become insufficient for individuals needs or for the stand as a whole. Since density by itself is not a good indicator of competition between component species, other expressions -like Reineke’s stand density index (SDI) - have been proposed as suitable indicators of site occupancy and competition. Specific objectives of this research are: a) to develop density - size relationships and relative density indexes for aspen and white spruce mixtures and, b) to investigate the effect of composition and site quality on maximum density - size relationships and stand growth rates. We are using data from permanent sample plots for trembling aspen ñ white spruce stands from western Canada (Alberta, Saskatchewan and Manitoba) to examine the usefulness of density - size relationships in mixed and pure stands of these species. Modeling of...
Establishing white spruce (Picea glauca (Moench) Voss) by planting it under established aspen (Po... more Establishing white spruce (Picea glauca (Moench) Voss) by planting it under established aspen (Populus tremuloides Michx.), stands has substantial potential as a technique for regenerating boreal mixedwood stands. The presence of an aspen overstory serves to ameliorate frost and winter injury problems and suppresses understory vegetation that may compete with white spruce. In this study we examine the growth of white spruce during the first 10 years after being planted underneath a 39-year-old stand of trembling aspen following thinning and fertilization. Results indicate successful establishment and reasonable growth rates of white spruce planted under thinned and unthinned aspen stands, even with aspen basal area of 51 m2 ha−1. Thinning of overstory aspen to 1000 or 2000 stems ha−1 did not increase light reaching seedlings, but did result in improvements in light above the shrub layer and in diameter and height growth of the underplanted seedlings. However, these increases in growth of underplanted spruce may not justify the expense of thinnings. Fertilization of these stands prior to planting had no effect on spruce growth. Growth of spruce underplanted at this site near Fort Nelson was similar to that at two other stands near Dawson Creek, B.C.Information on treatment effects on light, beam fraction, air temperature, and soil temperature are presented. Measurements of light obtained using LAI-2000 and hemispherical photography were compared with those obtained from hourly PPFD measurements. Results indicate that while both methods provide estimates of transmittance that are highly correlated with those provided by actual light measurements, they provide substantial underestimates of actual light levels.
While aspen (Populus tremuloides Michx.) cover provides protection from growing season radiative ... more While aspen (Populus tremuloides Michx.) cover provides protection from growing season radiative frosts, reduced light levels can limit growth of understory white spruce (Picea glauca (Moench) Voss). The creation of openings around individual spruce can provide more light, but the chance of radiative frost damage increases as gaps become larger. We examined the relationship between opening size and light and
On productive sites, young paper birch (Betula papyrifera Marsh.) outgrows most of the conifers w... more On productive sites, young paper birch (Betula papyrifera Marsh.) outgrows most of the conifers with which it is associated. Due to its dominant position in the canopy, and the potentially high densities of birch regeneration found on some sites, its presence may lead to a reduction in the amount of light reaching subordinate conifers. To evaluate the potential use of
Preliminary results indicate that patterns of tree growth are related to microclimatic gradients ... more Preliminary results indicate that patterns of tree growth are related to microclimatic gradients in these openings. Height growth of the various tree species reflects their tolerance to drought and shade in openings. Among the tree species evaluated, Western hemlock and Engelmann spruce were best suited at the south edge and in the intact forest, but Douglas fir performed best at
Plant size often influences shade tolerance but relatively few studies have considered the functi... more Plant size often influences shade tolerance but relatively few studies have considered the functional response of taller plants to contrasting light environments. Several boreal and sub-boreal Abies, Picea and Pinus species were studied along a light (0-90% full sunlight) and size (30-400-cm high) gradient to examine the interactive influence of tree size and light availability on aboveground biomass distribution. Sampling was conducted in two regions of Canada: (A) British Columbia, for Abies lasiocarpa (Hook.) Nutt., the Picea glauca (Moench.) Voss x P. engelmannii Parry ex. Engelm. complex and Pinus contorta Dougl. var. latifolia Engelm.; and (B) Quebec, for Abies balsamea (L.) Mill., Picea glauca (Moench. Voss) and Pinus banksiana (Lamb.). All biomass distribution traits investigated varied with size, and most showed a significant interaction with both size and light, which resulted in increasing divergences among light classes as size increased. For example, the proportion of needle mass decreased as size increased but the rate of decrease was much greater in saplings growing at below 10% full sunlight. Needle area ratio (total needle area:aboveground mass) followed a similar pattern, but decreased more rapidly with increasing tree size for small trees up to 1 m tall. The proportion of needle biomass (needle mass ratio) was always lower in taller trees (i.e., > 1 m tall) than in small trees (< 1 m tall) and increasingly so at the lowest solar irradiances (0-10% full sunlight). Thus, extrapolating the functional response to light from small seedling to taller individuals is not always appropriate.
Canadian Journal of Forest Research-revue Canadienne De Recherche Forestiere, 2003
Five years after spacing a young, 11 m tall paper birch (Betula papyrifera Marsh.) stand, we exam... more Five years after spacing a young, 11 m tall paper birch (Betula papyrifera Marsh.) stand, we examine rela- tionships between growth of understory white spruce (Picea glauca (Moench) Voss), subalpine fir (Abies lasiocarpa (Hook.) Nutt.), and level of birch retention. Our objectives were to evaluate the effectiveness of selected measures of competition for estimating the effects of the residual birch
ABSTRACT The effectiveness of competition indices for predicting light transmittance and white sp... more ABSTRACT The effectiveness of competition indices for predicting light transmittance and white spruce (Picea glauca (Moench) Voss) growth were examined across trembling aspen (Populus tremuloides Michx.) density gradients using sites from a long-term study of mixedwood growth and development in Alberta and Saskatchewan. Competition indices based on density (number of trees, basal area, and spacing factor), distance-dependent and -independent size ratio (Hegyi's and Lorimer's), and crown characteristics (crown volume, surface area, and cross-sectional area) were tested. Transmittance was effectively predicted by crown competition indices followed closely by aspen basal area and size ratio indices. Models of spruce growth indicated better results for stem volume compared with diameter or height. Competition alone accounted for less than 60% of stem growth variation, with basal area and transmittance providing some of the best models. The predictive ability of spruce growth was increased up to 93% by adding initial size as a second explanatory variable. In this respect, initial diameter was superior to initial height, crown volume, and surface area. Relationships between competition, transmittance, and spruce growth were found to differ significantly between geographical locations. These results suggest the need for local development of models relating tree growth to competition.
The influence of aspen ( Populus tremuloides Michx.) and herbaceous (forb and grass) vegetation o... more The influence of aspen ( Populus tremuloides Michx.) and herbaceous (forb and grass) vegetation on resource availability and white spruce ( Picea glauca (Moench) Voss) growth were examined as part of a long-term experiment established in 2002 near Whitecourt, Alberta, Canada. ...
ABSTRACT Vertical and horizontal patterns of light within gaps and expansion of trees into gaps w... more ABSTRACT Vertical and horizontal patterns of light within gaps and expansion of trees into gaps were examined in young stands dominated by trembling aspen (Populus tremuloides Michx.) in northeastern British Columbia and northwestern Alberta. Lateral growth of branches of aspen edge trees averaged 15.2 cm/year and was similar to crown expansion rates reported for edge trees in eastern North America. Branches growing into gaps were significantly longer than those growing away from gaps and are likely to lead to gap shrinkage and reductions in light within gaps. However, height growth of edge trees was not significantly different from that of trees within the surrounding stands. Models describing relationships between diffuse transmittance and locations within gaps and surrounding stand height were developed in this paper. Sky view angle (SVA) was found to be effective for predicting transmittance to different locations within gaps. When SVA values exceed 1.2 (at the B.C. sites), white spruce (Picea glauca (Moench) Voss) will receive <40% of full sunlight, which is less than optimal for spruce height growth.
Effectiveutilization of a patch or cluster approach to growing aspen-white spruce mixtures in the... more Effectiveutilization of a patch or cluster approach to growing aspen-white spruce mixtures in the boreal forest requires an understanding of how the faster growing aspen patches influence microclimate and spruce growth in adjacent spruce patches. In this paper we examine, how young (11- 13 year old) aspen (Populus tremuloides Michx) patches influence microclimatic conditions in adjacent openings and how these
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Papers by Philip Comeau