The Experts below are selected from a list of 225 Experts worldwide ranked by ideXlab platform
Douglas A Maguire - One of the best experts on this subject based on the ideXlab platform.
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sources of within and between stand variability in specific leaf area of three ecologically distinct conifer species
Annals of Forest Science, 2008Co-Authors: Aaron R Weiskittel, Hailemariam Temesgen, Duncan S Wilson, Douglas A MaguireAbstract:Specific leaf area (SLA) is an important ecophysiological variable, but its variability within and between stands has rarely been simultaneously examined and modeled across multiple species. Extensive datasets on SLA in coastal Douglas-fir (Pseudotsuga menziesii var. menziesii (Mirb.) Franco), hybrid Spruce (Picea engelmannii Parry × Picea glauca (Moench) Voss × Picea sitchensis (Bong.) Carr.), and ponderosa pine (Pinus ponderosa Dougl. ex P. & C. Laws.) were used to estimate variability of SLA within a canopy and its relationship to Tree- and stand-level covariates, and to predict SLA at various locations in Tree crowns. Also, in the case of hybrid Spruce, variation in SLA due to different relative horizontal lengths from the bole was examined. In all species, SLA systematically increased from Tree tip to crown base and decreased with foliage age class. Cardinal direction did not have a highly significant influence in either Douglas-fir or hybrid Spruce, but SLA did significantly decrease from branch tip to bole in hybrid Spruce. Tree- and stand-level (e.g. density, site index) factors had relatively little influence on SLA, but stand age did have a significant positive influence. For ponderosa pine, a significant relationship between canopy mean current-year SLA and carbon isotope discrimination was also found, suggesting the importance of water stress in this species. An equation was fitted to estimate SLA at various points in the canopy for each species and foliage age class using absolute height in the canopy, relative vertical height in the Tree, and stand age.
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Sources of within- and between-stand variability in specific leaf area of three ecologically distinct conifer species
Annals of Forest Science, 2008Co-Authors: Aaron R Weiskittel, Hailemariam Temesgen, Duncan S Wilson, Douglas A MaguireAbstract:Specific leaf area (SLA) is an important ecophysiological variable, but its variability within and between stands has rarely been simultaneously examined and modeled across multiple species. Extensive datasets on SLA in coastal Douglas-fir ( Pseudotsuga menziesii var. menziesii (Mirb.) Franco), hybrid Spruce ( Picea engelmannii Parry × Picea glauca (Moench) Voss × Picea sitchensis (Bong.) Carr.), and ponderosa pine ( Pinus ponderosa Dougl. ex P. & C. Laws.) were used to estimate variability of SLA within a canopy and its relationship to Tree- and stand-level covariates, and to predict SLA at various locations in Tree crowns. Also, in the case of hybrid Spruce, variation in SLA due to different relative horizontal lengths from the bole was examined. In all species, SLA systematically increased from Tree tip to crown base and decreased with foliage age class. Cardinal direction did not have a highly significant influence in either Douglas-fir or hybrid Spruce, but SLA did significantly decrease from branch tip to bole in hybrid Spruce. Tree- and stand-level (e.g. density, site index) factors had relatively little influence on SLA, but stand age did have a significant positive influence. For ponderosa pine, a significant relationship between canopy mean current-year SLA and carbon isotope discrimination was also found, suggesting the importance of water stress in this species. An equation was fitted to estimate SLA at various points in the canopy for each species and foliage age class using absolute height in the canopy, relative vertical height in the Tree, and stand age. La surface spécifique des feuilles (SLA) est un paramètre écophysiologique important mais sa variabilité intra et inter-peuplements n’a jamais été examinée et modélisée sur des gammes larges d’espèces. Des jeux de données très détaillés de SLA de Douglas côtiers [ Pseudotsuga menziesii var. menziesii (Mirb.) Franco], d’épicéas hybrides ( Picea engelmannii Parry × Picea glauca (Moench) Voss × Picea sitchensis (Bong.) Carr), et de pins ponderosa ( Pinus ponderosa Dougl. ex P. & C. Laws.) ont été mobilisés pour évaluer la variabilité de SLA dans une canopée. Les relations entre SLA et des covariables à l’échelle de l’arbre ou du peuplement ont été précisées, un modèle prédictif de SLA à différents niveaux dans les couronnes a été construit. Dans le cas de l’épicéa, l’impact de la distance de branche entre l’aiguille et le tronc a également été testé. Dans toutes les espèces, SLA augmentait systématiquement du sommet des arbres à la base de la couronne, et diminuait avec la classe d’âge des aiguilles. La direction cardinale n’avait guère d’influence sur SLA ni dans le cas du Douglas ni dans celui de l’épicéa; mais SLA diminuait systématiquement depuis l’extrémité des branches vers le tronc. Les facteurs arbre et peuplement (comme la densité, l’indice de productivité de la station) n’avaient que peu d’impact sur SLA alors que l’âge du peuplement avait un effet significatif et positif. Pour le pin ponderosa, une relation significative a été détectée entre la valeur moyenne de SLA des aiguilles de l’année et la discrimination isotopique du carbone, ce qui suggère l’impact des contraintes hydriques pour cette espèce. Un modèle de prédiction de SLA à différentes positions dans la canopée a été ajusté sur les données de chaque espèce et classe d’âge, en se basant sur la hauteur dans la canopée, la hauteur relative dans l’arbre et l’âge du peuplement.
Aaron R Weiskittel - One of the best experts on this subject based on the ideXlab platform.
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sources of within and between stand variability in specific leaf area of three ecologically distinct conifer species
Annals of Forest Science, 2008Co-Authors: Aaron R Weiskittel, Hailemariam Temesgen, Duncan S Wilson, Douglas A MaguireAbstract:Specific leaf area (SLA) is an important ecophysiological variable, but its variability within and between stands has rarely been simultaneously examined and modeled across multiple species. Extensive datasets on SLA in coastal Douglas-fir (Pseudotsuga menziesii var. menziesii (Mirb.) Franco), hybrid Spruce (Picea engelmannii Parry × Picea glauca (Moench) Voss × Picea sitchensis (Bong.) Carr.), and ponderosa pine (Pinus ponderosa Dougl. ex P. & C. Laws.) were used to estimate variability of SLA within a canopy and its relationship to Tree- and stand-level covariates, and to predict SLA at various locations in Tree crowns. Also, in the case of hybrid Spruce, variation in SLA due to different relative horizontal lengths from the bole was examined. In all species, SLA systematically increased from Tree tip to crown base and decreased with foliage age class. Cardinal direction did not have a highly significant influence in either Douglas-fir or hybrid Spruce, but SLA did significantly decrease from branch tip to bole in hybrid Spruce. Tree- and stand-level (e.g. density, site index) factors had relatively little influence on SLA, but stand age did have a significant positive influence. For ponderosa pine, a significant relationship between canopy mean current-year SLA and carbon isotope discrimination was also found, suggesting the importance of water stress in this species. An equation was fitted to estimate SLA at various points in the canopy for each species and foliage age class using absolute height in the canopy, relative vertical height in the Tree, and stand age.
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Sources of within- and between-stand variability in specific leaf area of three ecologically distinct conifer species
Annals of Forest Science, 2008Co-Authors: Aaron R Weiskittel, Hailemariam Temesgen, Duncan S Wilson, Douglas A MaguireAbstract:Specific leaf area (SLA) is an important ecophysiological variable, but its variability within and between stands has rarely been simultaneously examined and modeled across multiple species. Extensive datasets on SLA in coastal Douglas-fir ( Pseudotsuga menziesii var. menziesii (Mirb.) Franco), hybrid Spruce ( Picea engelmannii Parry × Picea glauca (Moench) Voss × Picea sitchensis (Bong.) Carr.), and ponderosa pine ( Pinus ponderosa Dougl. ex P. & C. Laws.) were used to estimate variability of SLA within a canopy and its relationship to Tree- and stand-level covariates, and to predict SLA at various locations in Tree crowns. Also, in the case of hybrid Spruce, variation in SLA due to different relative horizontal lengths from the bole was examined. In all species, SLA systematically increased from Tree tip to crown base and decreased with foliage age class. Cardinal direction did not have a highly significant influence in either Douglas-fir or hybrid Spruce, but SLA did significantly decrease from branch tip to bole in hybrid Spruce. Tree- and stand-level (e.g. density, site index) factors had relatively little influence on SLA, but stand age did have a significant positive influence. For ponderosa pine, a significant relationship between canopy mean current-year SLA and carbon isotope discrimination was also found, suggesting the importance of water stress in this species. An equation was fitted to estimate SLA at various points in the canopy for each species and foliage age class using absolute height in the canopy, relative vertical height in the Tree, and stand age. La surface spécifique des feuilles (SLA) est un paramètre écophysiologique important mais sa variabilité intra et inter-peuplements n’a jamais été examinée et modélisée sur des gammes larges d’espèces. Des jeux de données très détaillés de SLA de Douglas côtiers [ Pseudotsuga menziesii var. menziesii (Mirb.) Franco], d’épicéas hybrides ( Picea engelmannii Parry × Picea glauca (Moench) Voss × Picea sitchensis (Bong.) Carr), et de pins ponderosa ( Pinus ponderosa Dougl. ex P. & C. Laws.) ont été mobilisés pour évaluer la variabilité de SLA dans une canopée. Les relations entre SLA et des covariables à l’échelle de l’arbre ou du peuplement ont été précisées, un modèle prédictif de SLA à différents niveaux dans les couronnes a été construit. Dans le cas de l’épicéa, l’impact de la distance de branche entre l’aiguille et le tronc a également été testé. Dans toutes les espèces, SLA augmentait systématiquement du sommet des arbres à la base de la couronne, et diminuait avec la classe d’âge des aiguilles. La direction cardinale n’avait guère d’influence sur SLA ni dans le cas du Douglas ni dans celui de l’épicéa; mais SLA diminuait systématiquement depuis l’extrémité des branches vers le tronc. Les facteurs arbre et peuplement (comme la densité, l’indice de productivité de la station) n’avaient que peu d’impact sur SLA alors que l’âge du peuplement avait un effet significatif et positif. Pour le pin ponderosa, une relation significative a été détectée entre la valeur moyenne de SLA des aiguilles de l’année et la discrimination isotopique du carbone, ce qui suggère l’impact des contraintes hydriques pour cette espèce. Un modèle de prédiction de SLA à différentes positions dans la canopée a été ajusté sur les données de chaque espèce et classe d’âge, en se basant sur la hauteur dans la canopée, la hauteur relative dans l’arbre et l’âge du peuplement.
Lauriane Dinis - One of the best experts on this subject based on the ideXlab platform.
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Tree-ring stable isotopes for regional discharge reconstruction in eastern Labrador and teleconnection with the Arctic Oscillation
Climate Dynamics, 2019Co-Authors: Lauriane Dinis, Christian Bégin, Martine Savard, Joëlle Marion, Pierre Brigode, Cristian AlvarezAbstract:In northeastern Canada (Labrador), instrumental climatic data cover less than 70 years and long reconstructions from natural archives are non-existent. This study specifically aims at helping filling this gap of knowledge by testing the possibility of reconstructing the regional 1800–2009 discharge of the lower Churchill River from black Spruce Tree-ring δ13C and δ18O series. The results illustrate direct relationships of summer climatic variables/derived parameter (maximum temperature, total precipitation and vapor pressure deficit) with Tree-ring isotope values. Importantly, they show an inverse correlation between combined Tree-ring isotope series and regional river discharge due to common climate forcing. To a lesser extent, transpiration also affects the river discharge and Tree-ring isotopic compositions. The reconstructed river discharge series agrees with an independent reconstruction based on the ANATEM method (1880–2009 period). The agreement between the two reconstructions validates the two approaches for reconstructing regional hydroclimatic conditions at high latitudes. Moreover, the reconstructions suggest that summer discharge has decreased over the past 200 years in eastern Labrador and more broadly at the Québec-Labrador peninsula scale. This trend correlates with the long-term summer Arctic Oscillation (AO) that influences summer regional climatic conditions. This research contributes with other studies to build up observations linking summer AO and eastern Canada climatic conditions, and calls for research on mechanisms explaining these relationships during summer.
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Tree ring stable isotopes for regional discharge reconstruction in eastern labrador and teleconnection with the arctic oscillation
Climate Dynamics, 2019Co-Authors: Lauriane Dinis, Martine M. Savard, Christian Bégin, Joëlle Marion, Pierre Brigode, Cristian AlvarezAbstract:In northeastern Canada (Labrador), instrumental climatic data cover less than 70 years and long reconstructions from natural archives are non-existent. This study specifically aims at helping filling this gap of knowledge by testing the possibility of reconstructing the regional 1800–2009 discharge of the lower Churchill River from black Spruce Tree-ring δ13C and δ18O series. The results illustrate direct relationships of summer climatic variables/derived parameter (maximum temperature, total precipitation and vapor pressure deficit) with Tree-ring isotope values. Importantly, they show an inverse correlation between combined Tree-ring isotope series and regional river discharge due to common climate forcing. To a lesser extent, transpiration also affects the river discharge and Tree-ring isotopic compositions. The reconstructed river discharge series agrees with an independent reconstruction based on the ANATEM method (1880–2009 period). The agreement between the two reconstructions validates the two approaches for reconstructing regional hydroclimatic conditions at high latitudes. Moreover, the reconstructions suggest that summer discharge has decreased over the past 200 years in eastern Labrador and more broadly at the Quebec-Labrador peninsula scale. This trend correlates with the long-term summer Arctic Oscillation (AO) that influences summer regional climatic conditions. This research contributes with other studies to build up observations linking summer AO and eastern Canada climatic conditions, and calls for research on mechanisms explaining these relationships during summer.
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Puzzling Zn isotopes in Spruce Tree-ring series
Chemical Geology, 2018Co-Authors: Lauriane Dinis, Paul R. Gammon, Martine M. Savard, Christian Bégin, Isabelle Girard, Judy E. VaiveAbstract:Abstract Zinc (Zn) isotopes have shown promise for investigating biogeochemical processes and tracing sources of Zn for environmental studies. This study, the first in its kind, investigates Zn isotopic ratios in Tree rings and soils of two sites in the Northern Athabasca Oil Sands Region (NAOSR) of Alberta, Canada. To this end, we have developed an appropriate protocol to analyze Tree-ring δ66Zn values by pooling year-equivalent Tree rings of four individual Trees for both sites. The results of combined Tree-ring Zn concentrations show minimal variation in heartwood, with a statistically significant decrease after 1979 and 1986 for site 1 and site 2, respectively. For site 1, Tree-ring δ66ZnJMC Lyon ratios vary between 0.83 ± 0.08 to 0.54 ± 0.07‰ with a statistically significant decrease from 1877 to 2008. For site 2, δ66ZnJMC Lyon ratios range from 0.78 ± 0.02 to 0.59 ± 0.07‰ with the lowest values obtained for the outermost ring closest to the bark. However, this site does not display statistically significant long-term trend. In comparison to the Tree rings, adsorbed Zn within soil organic horizons is relatively enriched in heavy isotopes (δ66ZnJMC Lyon of 1.00 ± 0.20 to 1.12 ± 0.10 and 0.81 ± 0.10 to 0.86 ± 0.06‰ for sites 1 and 2, respectively). Tree-ring and soil organic horizons δ66Zn values are also substantially heavier than the value reported for adsorbed Zn in NAOSR tailing sands (δ66ZnJMC Lyon = 0.35 ± 0.06‰). The heavy signature in the organic horizons may be a product of Zn biogeochemical cycling through soil processes and uptake by Trees, although Zn atmospheric deposition from the NAOSR cannot be discounted. On the other hand, Tree physiological processes, particularly radial translocation, could have potentially influenced the studied Tree-ring Zn concentration and isotopic characteristics. However, this mechanism has not received substantial research. The δ66Zn analyses in different wood components are required before its influence on δ66Zn values can be properly assessed and Tree-ring δ66Zn can be used as environmental indicators.
Cristian Alvarez - One of the best experts on this subject based on the ideXlab platform.
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Tree-ring stable isotopes for regional discharge reconstruction in eastern Labrador and teleconnection with the Arctic Oscillation
Climate Dynamics, 2019Co-Authors: Lauriane Dinis, Christian Bégin, Martine Savard, Joëlle Marion, Pierre Brigode, Cristian AlvarezAbstract:In northeastern Canada (Labrador), instrumental climatic data cover less than 70 years and long reconstructions from natural archives are non-existent. This study specifically aims at helping filling this gap of knowledge by testing the possibility of reconstructing the regional 1800–2009 discharge of the lower Churchill River from black Spruce Tree-ring δ13C and δ18O series. The results illustrate direct relationships of summer climatic variables/derived parameter (maximum temperature, total precipitation and vapor pressure deficit) with Tree-ring isotope values. Importantly, they show an inverse correlation between combined Tree-ring isotope series and regional river discharge due to common climate forcing. To a lesser extent, transpiration also affects the river discharge and Tree-ring isotopic compositions. The reconstructed river discharge series agrees with an independent reconstruction based on the ANATEM method (1880–2009 period). The agreement between the two reconstructions validates the two approaches for reconstructing regional hydroclimatic conditions at high latitudes. Moreover, the reconstructions suggest that summer discharge has decreased over the past 200 years in eastern Labrador and more broadly at the Québec-Labrador peninsula scale. This trend correlates with the long-term summer Arctic Oscillation (AO) that influences summer regional climatic conditions. This research contributes with other studies to build up observations linking summer AO and eastern Canada climatic conditions, and calls for research on mechanisms explaining these relationships during summer.
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Tree ring stable isotopes for regional discharge reconstruction in eastern labrador and teleconnection with the arctic oscillation
Climate Dynamics, 2019Co-Authors: Lauriane Dinis, Martine M. Savard, Christian Bégin, Joëlle Marion, Pierre Brigode, Cristian AlvarezAbstract:In northeastern Canada (Labrador), instrumental climatic data cover less than 70 years and long reconstructions from natural archives are non-existent. This study specifically aims at helping filling this gap of knowledge by testing the possibility of reconstructing the regional 1800–2009 discharge of the lower Churchill River from black Spruce Tree-ring δ13C and δ18O series. The results illustrate direct relationships of summer climatic variables/derived parameter (maximum temperature, total precipitation and vapor pressure deficit) with Tree-ring isotope values. Importantly, they show an inverse correlation between combined Tree-ring isotope series and regional river discharge due to common climate forcing. To a lesser extent, transpiration also affects the river discharge and Tree-ring isotopic compositions. The reconstructed river discharge series agrees with an independent reconstruction based on the ANATEM method (1880–2009 period). The agreement between the two reconstructions validates the two approaches for reconstructing regional hydroclimatic conditions at high latitudes. Moreover, the reconstructions suggest that summer discharge has decreased over the past 200 years in eastern Labrador and more broadly at the Quebec-Labrador peninsula scale. This trend correlates with the long-term summer Arctic Oscillation (AO) that influences summer regional climatic conditions. This research contributes with other studies to build up observations linking summer AO and eastern Canada climatic conditions, and calls for research on mechanisms explaining these relationships during summer.
Hailemariam Temesgen - One of the best experts on this subject based on the ideXlab platform.
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sources of within and between stand variability in specific leaf area of three ecologically distinct conifer species
Annals of Forest Science, 2008Co-Authors: Aaron R Weiskittel, Hailemariam Temesgen, Duncan S Wilson, Douglas A MaguireAbstract:Specific leaf area (SLA) is an important ecophysiological variable, but its variability within and between stands has rarely been simultaneously examined and modeled across multiple species. Extensive datasets on SLA in coastal Douglas-fir (Pseudotsuga menziesii var. menziesii (Mirb.) Franco), hybrid Spruce (Picea engelmannii Parry × Picea glauca (Moench) Voss × Picea sitchensis (Bong.) Carr.), and ponderosa pine (Pinus ponderosa Dougl. ex P. & C. Laws.) were used to estimate variability of SLA within a canopy and its relationship to Tree- and stand-level covariates, and to predict SLA at various locations in Tree crowns. Also, in the case of hybrid Spruce, variation in SLA due to different relative horizontal lengths from the bole was examined. In all species, SLA systematically increased from Tree tip to crown base and decreased with foliage age class. Cardinal direction did not have a highly significant influence in either Douglas-fir or hybrid Spruce, but SLA did significantly decrease from branch tip to bole in hybrid Spruce. Tree- and stand-level (e.g. density, site index) factors had relatively little influence on SLA, but stand age did have a significant positive influence. For ponderosa pine, a significant relationship between canopy mean current-year SLA and carbon isotope discrimination was also found, suggesting the importance of water stress in this species. An equation was fitted to estimate SLA at various points in the canopy for each species and foliage age class using absolute height in the canopy, relative vertical height in the Tree, and stand age.
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Sources of within- and between-stand variability in specific leaf area of three ecologically distinct conifer species
Annals of Forest Science, 2008Co-Authors: Aaron R Weiskittel, Hailemariam Temesgen, Duncan S Wilson, Douglas A MaguireAbstract:Specific leaf area (SLA) is an important ecophysiological variable, but its variability within and between stands has rarely been simultaneously examined and modeled across multiple species. Extensive datasets on SLA in coastal Douglas-fir ( Pseudotsuga menziesii var. menziesii (Mirb.) Franco), hybrid Spruce ( Picea engelmannii Parry × Picea glauca (Moench) Voss × Picea sitchensis (Bong.) Carr.), and ponderosa pine ( Pinus ponderosa Dougl. ex P. & C. Laws.) were used to estimate variability of SLA within a canopy and its relationship to Tree- and stand-level covariates, and to predict SLA at various locations in Tree crowns. Also, in the case of hybrid Spruce, variation in SLA due to different relative horizontal lengths from the bole was examined. In all species, SLA systematically increased from Tree tip to crown base and decreased with foliage age class. Cardinal direction did not have a highly significant influence in either Douglas-fir or hybrid Spruce, but SLA did significantly decrease from branch tip to bole in hybrid Spruce. Tree- and stand-level (e.g. density, site index) factors had relatively little influence on SLA, but stand age did have a significant positive influence. For ponderosa pine, a significant relationship between canopy mean current-year SLA and carbon isotope discrimination was also found, suggesting the importance of water stress in this species. An equation was fitted to estimate SLA at various points in the canopy for each species and foliage age class using absolute height in the canopy, relative vertical height in the Tree, and stand age. La surface spécifique des feuilles (SLA) est un paramètre écophysiologique important mais sa variabilité intra et inter-peuplements n’a jamais été examinée et modélisée sur des gammes larges d’espèces. Des jeux de données très détaillés de SLA de Douglas côtiers [ Pseudotsuga menziesii var. menziesii (Mirb.) Franco], d’épicéas hybrides ( Picea engelmannii Parry × Picea glauca (Moench) Voss × Picea sitchensis (Bong.) Carr), et de pins ponderosa ( Pinus ponderosa Dougl. ex P. & C. Laws.) ont été mobilisés pour évaluer la variabilité de SLA dans une canopée. Les relations entre SLA et des covariables à l’échelle de l’arbre ou du peuplement ont été précisées, un modèle prédictif de SLA à différents niveaux dans les couronnes a été construit. Dans le cas de l’épicéa, l’impact de la distance de branche entre l’aiguille et le tronc a également été testé. Dans toutes les espèces, SLA augmentait systématiquement du sommet des arbres à la base de la couronne, et diminuait avec la classe d’âge des aiguilles. La direction cardinale n’avait guère d’influence sur SLA ni dans le cas du Douglas ni dans celui de l’épicéa; mais SLA diminuait systématiquement depuis l’extrémité des branches vers le tronc. Les facteurs arbre et peuplement (comme la densité, l’indice de productivité de la station) n’avaient que peu d’impact sur SLA alors que l’âge du peuplement avait un effet significatif et positif. Pour le pin ponderosa, une relation significative a été détectée entre la valeur moyenne de SLA des aiguilles de l’année et la discrimination isotopique du carbone, ce qui suggère l’impact des contraintes hydriques pour cette espèce. Un modèle de prédiction de SLA à différentes positions dans la canopée a été ajusté sur les données de chaque espèce et classe d’âge, en se basant sur la hauteur dans la canopée, la hauteur relative dans l’arbre et l’âge du peuplement.