Papers by Martin-Michel Gauthier
Journal of Forestry Research, 2018
We studied late-entry commercial thinning effects on growth, yield, and regeneration in a 48-year... more We studied late-entry commercial thinning effects on growth, yield, and regeneration in a 48-year-old jack pine (Pinus banksiana Lamb.) stand. Applied thinning intensities were 27, 32, and 47% of merchantable basal area (BA) excluding skidding trails. After 15 years, mean diameter at breast height of surviving trees in the 47% BA removal increased by 4.9 cm (25%) compared to the unthinned control. The 47% BA removal also increased gross merchantable volume (GMV) tree-1 by 46% compared to the control. The 27% BA removal had twice as much GMV ha-1 compared to the 47% BA removal after 15 years. Moreover, cumulative GMV ha-1 was much higher in the 27% BA removal than in the unthinned control. The highest thinning intensity produced larger trees on average, while the lowest thinning intensity maximized volume production per hectare. Maintenance of acceptable growing stock throughout the 15 year period in the 27% BA removal could provide other ecosystem functions such as biodiversity enhancement or wildlife habitat by delaying senescence. Regeneration data showed that a shift in species composition occurred in the understory. After 15 years, the understory was dominated by black spruce (Picea mariana (Mill.) B.S.P.), white birch (Betula papyrifera Marsh.), and trembling aspen (Populus tremuloides Michx.). If regenerating jack pine is an objective after final overstory removal, additional efforts will be needed to re-establish this species.
Trees, 2018
Key message Compared to in situ measurements, net photosynthesis and stomatal conductance were re... more Key message Compared to in situ measurements, net photosynthesis and stomatal conductance were reduced 3–6 min after leaf detachment in Quercus rubra and Quercus alba, and 9 min after leaf detachment in Juglans nigra.
Abstract
Collecting in situ gas-exchange measurements in canopies of mature trees is challenging, because the crown can be several meters above ground. Thus, we investigated the effect of detaching the leaf from the branch and time since detachment for three deciduous angiosperm species: black walnut (Juglans nigra), northern red oak (Quercus rubra), and white oak (Quercus alba). Results showed that net photosynthesis (A) was significantly reduced 3 min after leaf detachment in Quercus rubra, 6 min after leaf detachment in Q. alba, and 9 min after leaf detachment in J. nigra. Compared to the in situ measurement, a 72 ± 13% reduction (mean ± SE) in A occurred after 3 min in Q. rubra, a 74 ± 27% reduction in A occurred after 6 min in Q. alba, while a 41 ± 14% reduction in A occurred after 9 min in J. nigra. Furthermore, once the significant reduction in A occurred, it was maintained over the remaining time period for each species. Responses for stomatal conductance were similar to those of A. Results highlight the importance of measuring gas exchange in situ whenever possible. Otherwise, these results provide threshold time periods to carry out instantaneous gas-exchange measurements in the field for select hardwood species in which the canopy is difficult to access.
Forest Ecology and Management, 2018
While light is a primary driver of tree growth and development, other environmental variables are... more While light is a primary driver of tree growth and development, other environmental variables are also essential, including water, nutrients, and temperature. Ecophysiological studies have helped to uncover mechanisms underlying these interactive processes, but such trials have been mainly conducted on seedlings, with relatively few dealing with trees past the sapling stage. We used environmental and ecophysiological data collected on 28 trees (age 14–20 years) across three study sites in Indiana, USA for several growing seasons to identify variables that drive diameter growth of plantation-grown hardwoods past the sapling stage under non-limiting light conditions. Results showed that water stress (as reflected in leaf water potential) had the greatest influence on growth; relative diameter growth of black walnut (Juglans nigra L.), northern red oak (Quercus rubra L.), and white oak (Quercus alba L.) was reduced with increasing water stress. Compared to previous studies carried out with seedlings, results provide some evidence to suggest that ecophysiological responses to water stress may differ between seedlings, juveniles, and mature trees of the same species. Relative diameter growth of black walnut and northern red oak increased with increasing soil or leaf nitrogen. We did not find relationships between relative diameter growth of white oak and nutrient variables. Overall, these results have important implications for reforestation and forest management efforts in light of climate change.
Scandinavian Journal of Forest Research, 2018
Lack of available workforce in motor-manual operations has led to increased interest in mechanize... more Lack of available workforce in motor-manual operations has led to increased interest in mechanized precommercial thinning (PCT) treatments. We evaluated 15 years of growth and yield development of a very dense (27,000 stems ha–1) balsam fir (Abies balsamea (L.) Mill) and black spruce (Picea mariana (Mill.) B.S.P.) stand after six PCT treatments: (1) motor-manual (MAN), (2) motor-manual with crop tree release (MAN-C), (3) mechanized (MEC), (4) mechanized with residual patches (MEC-P), (5) semi-mechanized (mechanized followed by motor-manual, MEC-S), and (6) unthinned control (CON). Compared to CON, both MAN and MEC-S increased height of balsam fir study trees by 53–56% and diameter at breast height (DBH) by 57–58%. MAN-C and MEC-S increased DBH of black spruce study trees by 15–31% over all other treatments. The proportion of merchantable basal area (BA) was higher in MAN (62%) and MEC-S (56%) than in CON (22%) and MEC (25%), without a reduction in total BA. PCT treatments that provided a uniform distribution of potential crop trees (MAN, MEC-S) performed better than MAN-C and MEC-P, while MEC yielded the poorest responses. Our findings highlight the need to develop new tailored mechanized systems for high wood production and low operational cost.
Plant Ecology, 2018
We carried out a study to determine if bark type could reflect the growth potential of yellow bir... more We carried out a study to determine if bark type could reflect the growth potential of yellow birch (Betula alleghaniensis Britt.) and sugar maple (Acer saccharum Marsh.) at the northern limit of their range in Québec, Canada (47° N, 75° W). We measured a large sample of 266 trees that ranged in size from 95 to 712 mm in diameter at breast height, on two independent study sites. Our results suggest that trees with smooth bark type had mean 5-yr diameter increment 8 and 11 mm higher than trees with rough bark type, depending upon study site. Differences in growth of 8 and 11 mm represented 85% of the overall rough bark type increment in the first site and 78% of the overall rough bark type increment in the second site. The rapid identification of a tree’s growth potential using bark type could be of great use to practitioners because it avoids the need to bore trees to collect increment cores, which injures trees and may serve as an entry point for disease. Moreover, the proposed method helps protect or release the smallest trees with high growth potential and remove trees with low growth potential. While the proposed method is valuable to practitioners operating in uneven-aged forests, its applicability still needs to be tested in even-aged forests.
Forestry Chronicle, 2017
We used a permanent sample plot network established to monitor the effects of forest management p... more We used a permanent sample plot network established to monitor the effects of forest management practiced in mature northern hardwood and mixedwood stands in Québec, Canada to address two important questions related to tree mortality: (1) How does partial cutting affect tree mortality? (2) Which variables best explain tree mortality by different modes of death (standing death, uprooting or stem breakage)? Decennial tree deaths were lower after partial cutting than in unharvested plots, but the annual proportion of tree death was similar (1.25%·year-1). At the tree level, a risk-product classification demonstrated the strongest evidence on influencing total mortality, followed by species, the presence of a logging injury, and tree size. Annual temperature was the only climatic variable explaining variations in total risk of tree mortality , and always among the first three variables explaining differences among the three modes of death. The risk of standing death also increased with increasing annual precipitation, while the risk of stem breakage and, to a lesser extent, of being uprooted, decreased with increasing precipitation. Additionally, we found strong evidence to support the effect of the potassium/magnesium ratio of the humus layer on the risk of being uprooted. This information is critical to better understand tree mortality processes.
RÉSUMÉ
Nous avons utilisé les données de placettes permanentes établies pour suivre les effets de l'aménagement forestier dans des peuplements matures à dominance feuillue au Québec (Canada) dans le but de répondre à deux questions relatives à la mortalité des arbres : (1) Comment la coupe partielle affecte-t-elle le taux de mortalité des arbres? (2) Quelles variables expliquent le mieux la mortalité des arbres feuillus selon qu'ils sont morts sur pied, déracinés ou ont un tronc rompu? La mortalité décennale était moindre après une coupe partielle que dans les placettes non traitées, mais la proportion annuelle d'arbres morts était la même dans les deux (1,25 %·année-1). Parmi les variable étudiées, la classe de risque et de produit potentiel de l'arbre feuillu influençait le plus la probabilité globale de mortalité; elle était suivie par l' espèce, la présence d'une blessure de coupe, puis la dimension de l'arbre. La température annuelle était la seule variable climatique permettant d' expliquer la probabilité globale de mortalité des arbres, et l'une des trois variables les plus importantes pour les trois types de mort. Le risque de mourir sur pied augmentait aussi avec l'augmentation des précipitations annuelles, tandis que celui de rupture du tronc et, dans une moindre mesure, celui d' être déraciné diminuaient avec l'augmentation des précipitations. Finalement, nous avons observé que le risque de déracinement d'un arbre était influencé par le rapport potassium/magnésium dans la couche d'humus du sol. Ces informations sont importantes pour mieux comprendre les processus de mortalité des arbres.
Forest Science, 2016
We investigated short-term regeneration dynamics after group selection cutting with understory ve... more We investigated short-term regeneration dynamics after group selection cutting with understory vegetation control and soil scarification in a northern hardwood forest. We used three gap sizes based on mean height (H) of neighboring trees in a replicated experiment: small (0.75H), medium (1.25H), and large (1.75H) gaps. After 5 years, all gap sizes led to abundant density of yellow birch (Betula alleghaniensis Britt.) and sugar maple (Acer saccharum Marsh.) regeneration, associated with sufficient light (>38% of canopy transmittance), favorable seedbeds (50% of ground cover in disturbed leaf litter or exposed mineral soil), and reduced competition from noncommercial species due to vegetation control. We found no differences in tree species diversity patterns among gap sizes, but diversity patterns changed over time due to increased density of shade-tolerant conifers. After 5 years, yellow birch regeneration was positively influenced by increasing distance from the gap center and stand species composition, but negatively influenced by percent cover of undisturbed leaf litter, graminoid cover, and raspberry cover. The percent variation explained was relatively low (R2=0.26). Overall, group selection with soil scarification and vegetation control was successful in establishing desired tree species, especially yellow
birch and sugar maple, but further monitoring is required to determine its long-term efficacy.
Forest Ecology and Management, 2013
The introduction of the fungal pathogen Cryphonectria parasitica (Murr.) Barr. decimated American... more The introduction of the fungal pathogen Cryphonectria parasitica (Murr.) Barr. decimated American chestnut (Castanea dentata (Marsh.) Borkh.) throughout its native range in North America. A blight-resistant backcross hybrid form of American chestnut has been developed, and these backcross trees are likely to be incorporated into restoration programs in the near future. To help guide future afforestation efforts,
this study examined juvenile (five growing seasons) morphological and physiological competitive aspects of American chestnut grown in a plantation setting with northern red oak (Quercus rubra L.) and black cherry (Prunus serotina Ehrh.) in Indiana, USA. Species were grown in seven possible species combinations including both monospecific and polyspecific combinations at three densities (1x1 m, 2x2 m, and
3x3 m). Despite an initial advantage in height, American chestnut exhibited the lowest relative height growth in the 2x2 and 3x3 m spacings, resulting in less total height compared to the other two species 5 years after planting. Relative height growth, as well as final absolute heights, were comparable among species in the 1x1 m spacing. Black cherry exhibited 2–3 times greater relative ground-line diameter (GLD) growth compared to oak and chestnut at all spacings. Linear regressions showed that growth
was generally proportional to net photosynthesis (A) for all species. Increases in A likely resulted from increases in leaf nitrogen concentration. Chestnut exhibited lower A than cherry and oak in years 2 and 3, but no differences occurred in year 4. Additionally, chestnut had significantly higher predawn leaf water potential (leaf Wpd) in year 4, reflecting greater drought stress in cherry and oak. While black cherry grew most aggressively, northern red oak and American chestnut performed acceptably, with high survival rates and moderate growth, especially in the 1x1 mspacing. American chestnut had the poorest stem form overall, but fared better in the 1x1 m spacing where the crown competition factor (CCF) was highest. Hence, an intermediate spacing between 1x1 and 2x2 m could optimize chestnut’s growth and stem form. Mixture effects may be attributed mainly to individual species growth characteristics rather than inter-specific interactions during this juvenile developmental stage.
Forest Ecology and Management, 2015
We used long-term data collected from 22 study sites in northern hardwood stands comprised of sug... more We used long-term data collected from 22 study sites in northern hardwood stands comprised of sugar maple (Acer saccharum Marsh.), yellow birch (Betula alleghaniensis Britt.), and American beech (Fagus grandifolia Ehrh.) to establish relationships between sapling abundance and tree ingrowth. After 10 years, postharvest sapling density in the 6 cm diameter class (5.1–7.0 cm) showed linear relationships with ingrowth. Proportion of variation explained (r2) varied from 36% to 83% depending upon tree species and silvicultural treatment (partial cutting vs. uncut control). After 20 years, linear relationships were also established (r2 = 24–65%) between ingrowth and sapling density in the 2 cm diameter class (1.1–3.0 cm). From a wide pool of variables related to stand species composition, climate, physiography, and soil nutrients, postharvest sapling density was most strongly correlated to merchantable tree density (r = 0.43–0.75). Sugar maple sapling density was also positively correlated with base saturation and calcium saturation of the B horizon (r = 0.56 and 0.58). Over a 30-year period, the increase in American beech sapling basal area was substantial compared to mitigated increases found in sugar maple and yellow birch depending upon treatment. Our results provide useful information on integration of sapling data into forest management.
Annals of Forest Science, 2011
• Context: Walnuts (Juglans spp.) are ecologically and commercially important trees, yet synthesi... more • Context: Walnuts (Juglans spp.) are ecologically and commercially important trees, yet synthesis of past and current research findings on walnut ecophysiology is lacking, especially in terms of potential acclimation to climate change.
• Aims: This study aims to (1) investigate walnut ecophysiology by comparing its attributes to associated deciduous angiosperms, (2) address potential acclimation of walnut to climate change, and (3) identify areas for prioritization in future research.
• Results: There is considerable uncertainty regarding the magnitude of potential effects of climate change on walnut. Some studies tend to indicate walnut could be negatively impacted by climate change, while others do not. Walnut may be at a disadvantage due to its susceptibility to drought and frost injury in current growing regions given the
projected increases in temperature and extreme climatic events. Other regions that are currently considered cold for walnut growth may see increased establishment and growth depending upon the rate of temperature increase and the frequency and severity of extreme climatic events.
• Conclusion: Research investigating a combination of environmental factors, such as temperature, carbon dioxide, ozone, water, and nitrogen is needed to (1) better project climate change effects on walnut and (2) develop management strategies for walnut acclimation and adaptation to climate change.
Forest Ecology and Management, 2010
Ecophysiology of black walnut (Juglans nigra L.) along a vertical canopy gradient was studied in ... more Ecophysiology of black walnut (Juglans nigra L.) along a vertical canopy gradient was studied in a mixed species plantation for the first (2007) and second (2008) growing seasons after thinning to understand response mechanisms to increased resource availability. Parameters were affected by the thinning treatment in 2008 only. Thinned trees showed increased light-saturated maximum photosynthesis (Amax) from 2007 to 2008 compared to non-thinned trees. This response was likely due to increased light levels near thinned trees (vs. changes in water or nutrient status), because thinning did not affect midday leaf water potential (Cmd), average daily soil water content (SWC), or leaf nitrogen content per unit area (Na). Plantation thinning did not increase relative diameter growth during the experimental period. This may be due to low thinning intensity and mortality prior to thinning that reduced competition from first-tier neighbors. Certain leaf traits such as leaf mass per unit area (LMA) and Na increased from the bottom to the upper canopy position, but did not influence thinning responses. Distribution patterns of photosynthetic parameters through the vertical canopy gradient were less defined than leaf structural traits such as LMA and Na. Findings reflect black walnut’s large variability in response to thinning.
Forest Science, 2009
We studied physiological responses of mature black walnut (Juglans nigra L.) trees to determine t... more We studied physiological responses of mature black walnut (Juglans nigra L.) trees to determine the time necessary for photosynthetic adaptation to plantation thinning. Measurements were taken before treatment (July 25, 2007) and for the first 3 days after thinning (July 29, 30, and 31, 2007). Measurements did not continue in August because trees had developed leaf anthracnose and senescence was occurring, but measurements resumed on May 29, 2008 and July 29, 2008. Repeated measures of net photosynthetic rates (A) showed that thinned trees did not respond immediately to partial release, but nearly doubled in A compared with a 35% increase in control trees 1 year after thinning. Significant increases in light, leaf water status, relative humidity of the air, and nitrogen content per unit leaf area were also found in thinned trees 1 year after treatment. From these variables, light (r2 = 0.79) showed the strongest relationship with A. Results suggest that black walnut requires a full season before it responds to treatment when thinned late in the growing season. Thinning
earlier, such as in June, may trigger a more rapid adaptation in A of thinned trees that was not detected in our
study.
Northern Journal of Applied Forestry, 2010
We established a study to investigate short-term morphological responses of northern red oak (Que... more We established a study to investigate short-term morphological responses of northern red oak (Quercus rubra L.), white oak (Quercus alba L.), and black walnut (Juglans nigra L.) to a 43% basal area reduction in a mixed planting. Although the effect was not statistically confirmed, thinned northern red oak showed a 23% gain in relative diameter growth and a 25% gain in relative crown surface area expansion compared with nonthinned trees; white oak showed gains of 15 and 10%, respectively. Similar trends were found in percentage of basal area increase for northern red oak (45%) and white oak (37%). Black walnut did not appear to respond to thinning and may have been under less competition from first-tier neighbors than the oaks were. Both northern red oak and white oak were in intermediate and suppressed crown classes, whereas black walnut was in a codominant position. Trends from this study suggest that northern red oak and white oak may respond favorably to thinning when found in lower crown classes where the amount of competition from neighboring trees is high.
New Forests, 2015
We established a long-term experiment in a temperate mixedwood stand to evaluate the effectivenes... more We established a long-term experiment in a temperate mixedwood stand to evaluate the effectiveness of silvicultural treatments in regenerating a mixed-species cohort while maintaining the dominance of conifers. Silvicultural treatments included clearcutting using careful logging around advanced growth (CLAAG), uniform shelterwood (US), group shelterwood with (GS-s) or without scarification (GS), and an uncut control (control). After 10 years, height and ground-line diameter growth responses of advanced balsam fir (Abies balsamea [L.] Mill.) regeneration were substantial in CLAAG and GS compared to the control, and intermediate in US. Growth responses were proportional to increases in canopy light transmittance resulting from harvest. Advanced balsam fir regeneration had low mortality (\10 %) and a high potential for release as measured by the apical dominance ratio. At the stand level, however, a shift in species composition occurred in the regenerating cohort. Over the 10-year period, composition changed from conifer-dominated to hardwood-dominated in CLAAG, GS, and GS-s compared to the control. Scarification increased the magnitude of this shift by favoring shade-intolerant hardwoods. Results highlight the need to find a balance between releasing advance conifer regeneration and limiting competition from less desirable species.
The Forestry Chronicle, 2013
The use of gap-based silviculture and enrichment planting was tested in temperate mixedwood fores... more The use of gap-based silviculture and enrichment planting was tested in temperate mixedwood forests in eastern Canada. Four different sizes of canopy opening or patch cuts were applied to six stands in the maple–birch domain of Quebec. We evaluated the influence of opening size, cardinal quadrant within the opening, and distance from the forest edge of openings on white spruce height and ground-level diameter (GLD) five years after enrichment planting. At ≥5 m from the edge, initial canopy transmittance was generally >60% in all four canopy treatments. White spruce seedling height and GLD were lower within 10 m from the edge, and generally increased where understory light levels were higher. Seedling survival, height, and GLD in the smallest opening (0.05 ha) were comparable or higher than those found in relatively larger openings. The 0.05-ha opening that more closely emulates natural canopy gaps of temperate mixedwood forests provided satisfactory seedling development, and is therefore compatible with a gap-based stand dynamics approach to management of mixedwood stands in Quebec.
Forests, 2015
We evaluated the effectiveness of commercial thinning mainly from below (CT; 0, 26%, 32% and 40% ... more We evaluated the effectiveness of commercial thinning mainly from below (CT; 0, 26%, 32% and 40% merchantable basal area removals) in meeting wood production demands and developing structural heterogeneity in a balsam fir (Abies balsamea (L.) Mill) and spruce (Picea spp.) stand. After 10 years, 32%–40% removals showed a 12%–18% increase in mean diameter and 27%–38% increase in gross merchantable volume (GMV) per tree compared to the unthinned control. At the stand level, all thinning treatments generated as much cumulative GMV (harvested volume + GMV after 10 years) and gross sawlog volume per hectare as the unthinned control. As for stand structure, eight out of nine thinned experimental units showed increased structural heterogeneity after 10 years, i.e., irregular, positively-skewed diameter distribution with an elongated right tail toward larger trees. The diameter distribution in the unthinned control became more symmetric, unimodal and regular over time, with fewer saplings than at the beginning of the experiment and lower density of larger trees compared to CT. Regeneration density and stocking were abundant in all treatments, largely dominated by balsam fir. Results indicate that thinning can be used to meet wood production objectives and help develop structural heterogeneity in this forest.
Forests, 2015
We evaluated the effectiveness of commercial thinning mainly from below (CT; 0, 26%, 32% and 40% ... more We evaluated the effectiveness of commercial thinning mainly from below (CT; 0, 26%, 32% and 40% merchantable basal area removals) in meeting wood production demands and developing structural heterogeneity in a balsam fir (Abies balsamea (L.) Mill) and spruce (Picea spp.) stand. After 10 years, 32%-40% removals showed a 12%-18% increase in mean diameter and 27%-38% increase in gross merchantable volume (GMV) per tree compared to the unthinned control. At the stand level, all thinning treatments generated as much cumulative GMV (harvested volume + GMV after 10 years) and gross sawlog volume per hectare as the unthinned control. As for stand structure, eight out of nine thinned experimental units showed increased structural heterogeneity after 10 years, i.e., irregular, positively-skewed diameter distribution with an elongated right tail toward larger trees. The diameter distribution in the unthinned control became more symmetric, unimodal and regular over time, with fewer saplings than at the beginning of the experiment and lower density of larger trees compared to CT. Regeneration density and stocking were abundant in all treatments, largely dominated by balsam fir. Results indicate that thinning can be used to meet wood production objectives and help develop structural heterogeneity in this forest.
Forest Ecology and Management, 2012
We applied four precommercial thinning (PCT) intensities (unthinned control, 2.5, 3.0, and 3.5 m ... more We applied four precommercial thinning (PCT) intensities (unthinned control, 2.5, 3.0, and 3.5 m residual spacings) to aspen (Populus tremuloides Michx.) stems, while preserving understory balsam fir (Abies balsamea (L.) Mill.) in an even-aged stratified boreal mixedwood stand. We evaluated treatment influence on aspen and balsam fir growth, and regeneration dynamics over a 10-year period. Compared to the
unthinned control, PCT increased relative diameter increment of aspen saplings by 66–85% and relative basal area increment by 234–326%. Increases were similar among PCT treatments. Understory balsam fir regeneration >=1 m in height at time of thinning strongly benefited from PCT, with increases in height and crown width growth two to three times higher than in the control. The establishment of balsam fir regeneration, however, was not favored by PCT compared to the control. Our results show PCT increased tree size of individual aspen while promoting understory balsam fir growth in this type of stratified mixture. This approach should therefore be useful in limiting hardwood conversion in the boreal mixedwood forest at an early stage in stand development. Developing silvicultural approaches such as this one would be in line with the concept of ecosystem-based forest management.
Forest Ecology and Management, 2013
ABSTRACT We evaluated the effectiveness of the regular shelterwood system in mitigating water tab... more ABSTRACT We evaluated the effectiveness of the regular shelterwood system in mitigating water table rise and regenerating a new cohort while favoring red spruce (Picea rubens Sarg.) in an 80-year-old, red spruce – balsam fir (Abies balsamea (L.) Mill.) lowland site. We used an experimental design established in 1994, with four completely randomized blocks and five treatments (uncut control, low, moderate, and heavy shelterwood cuttings, and clearcutting). In 2006, final overstory removal was carried out in the three shelterwoods and we monitored the first five growing seasons after treatment. Results showed that final cut did not lead to significant watering-up during the 2006–2010 period compared to levels measured in 1999, but water table levels did not fully recover from shelterwood cutting or clearcutting compared to precut levels measured in 1994. Under conditions of abundant seed supply, poor drainage, and low herbaceous and noncommercial woody competition, clearcutting (0.25 ha patches) provided the best red spruce cohort in terms of regeneration density, stocking, and growth. Balsam fir and red maple (Acer rubrum L.) regeneration was abundant in both silvicultural systems. Regeneration density and stocking of red spruce, balsam fir, and all commercial broadleaf species were generally lower inside logging trails than between trails, likely due to disturbance by machinery. For poorly-drained lowland sites, findings indicate patch clearcutting may be more effective in regenerating red spruce than the regular shelterwood system.
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Papers by Martin-Michel Gauthier
Abstract
Collecting in situ gas-exchange measurements in canopies of mature trees is challenging, because the crown can be several meters above ground. Thus, we investigated the effect of detaching the leaf from the branch and time since detachment for three deciduous angiosperm species: black walnut (Juglans nigra), northern red oak (Quercus rubra), and white oak (Quercus alba). Results showed that net photosynthesis (A) was significantly reduced 3 min after leaf detachment in Quercus rubra, 6 min after leaf detachment in Q. alba, and 9 min after leaf detachment in J. nigra. Compared to the in situ measurement, a 72 ± 13% reduction (mean ± SE) in A occurred after 3 min in Q. rubra, a 74 ± 27% reduction in A occurred after 6 min in Q. alba, while a 41 ± 14% reduction in A occurred after 9 min in J. nigra. Furthermore, once the significant reduction in A occurred, it was maintained over the remaining time period for each species. Responses for stomatal conductance were similar to those of A. Results highlight the importance of measuring gas exchange in situ whenever possible. Otherwise, these results provide threshold time periods to carry out instantaneous gas-exchange measurements in the field for select hardwood species in which the canopy is difficult to access.
RÉSUMÉ
Nous avons utilisé les données de placettes permanentes établies pour suivre les effets de l'aménagement forestier dans des peuplements matures à dominance feuillue au Québec (Canada) dans le but de répondre à deux questions relatives à la mortalité des arbres : (1) Comment la coupe partielle affecte-t-elle le taux de mortalité des arbres? (2) Quelles variables expliquent le mieux la mortalité des arbres feuillus selon qu'ils sont morts sur pied, déracinés ou ont un tronc rompu? La mortalité décennale était moindre après une coupe partielle que dans les placettes non traitées, mais la proportion annuelle d'arbres morts était la même dans les deux (1,25 %·année-1). Parmi les variable étudiées, la classe de risque et de produit potentiel de l'arbre feuillu influençait le plus la probabilité globale de mortalité; elle était suivie par l' espèce, la présence d'une blessure de coupe, puis la dimension de l'arbre. La température annuelle était la seule variable climatique permettant d' expliquer la probabilité globale de mortalité des arbres, et l'une des trois variables les plus importantes pour les trois types de mort. Le risque de mourir sur pied augmentait aussi avec l'augmentation des précipitations annuelles, tandis que celui de rupture du tronc et, dans une moindre mesure, celui d' être déraciné diminuaient avec l'augmentation des précipitations. Finalement, nous avons observé que le risque de déracinement d'un arbre était influencé par le rapport potassium/magnésium dans la couche d'humus du sol. Ces informations sont importantes pour mieux comprendre les processus de mortalité des arbres.
birch and sugar maple, but further monitoring is required to determine its long-term efficacy.
this study examined juvenile (five growing seasons) morphological and physiological competitive aspects of American chestnut grown in a plantation setting with northern red oak (Quercus rubra L.) and black cherry (Prunus serotina Ehrh.) in Indiana, USA. Species were grown in seven possible species combinations including both monospecific and polyspecific combinations at three densities (1x1 m, 2x2 m, and
3x3 m). Despite an initial advantage in height, American chestnut exhibited the lowest relative height growth in the 2x2 and 3x3 m spacings, resulting in less total height compared to the other two species 5 years after planting. Relative height growth, as well as final absolute heights, were comparable among species in the 1x1 m spacing. Black cherry exhibited 2–3 times greater relative ground-line diameter (GLD) growth compared to oak and chestnut at all spacings. Linear regressions showed that growth
was generally proportional to net photosynthesis (A) for all species. Increases in A likely resulted from increases in leaf nitrogen concentration. Chestnut exhibited lower A than cherry and oak in years 2 and 3, but no differences occurred in year 4. Additionally, chestnut had significantly higher predawn leaf water potential (leaf Wpd) in year 4, reflecting greater drought stress in cherry and oak. While black cherry grew most aggressively, northern red oak and American chestnut performed acceptably, with high survival rates and moderate growth, especially in the 1x1 mspacing. American chestnut had the poorest stem form overall, but fared better in the 1x1 m spacing where the crown competition factor (CCF) was highest. Hence, an intermediate spacing between 1x1 and 2x2 m could optimize chestnut’s growth and stem form. Mixture effects may be attributed mainly to individual species growth characteristics rather than inter-specific interactions during this juvenile developmental stage.
• Aims: This study aims to (1) investigate walnut ecophysiology by comparing its attributes to associated deciduous angiosperms, (2) address potential acclimation of walnut to climate change, and (3) identify areas for prioritization in future research.
• Results: There is considerable uncertainty regarding the magnitude of potential effects of climate change on walnut. Some studies tend to indicate walnut could be negatively impacted by climate change, while others do not. Walnut may be at a disadvantage due to its susceptibility to drought and frost injury in current growing regions given the
projected increases in temperature and extreme climatic events. Other regions that are currently considered cold for walnut growth may see increased establishment and growth depending upon the rate of temperature increase and the frequency and severity of extreme climatic events.
• Conclusion: Research investigating a combination of environmental factors, such as temperature, carbon dioxide, ozone, water, and nitrogen is needed to (1) better project climate change effects on walnut and (2) develop management strategies for walnut acclimation and adaptation to climate change.
earlier, such as in June, may trigger a more rapid adaptation in A of thinned trees that was not detected in our
study.
unthinned control, PCT increased relative diameter increment of aspen saplings by 66–85% and relative basal area increment by 234–326%. Increases were similar among PCT treatments. Understory balsam fir regeneration >=1 m in height at time of thinning strongly benefited from PCT, with increases in height and crown width growth two to three times higher than in the control. The establishment of balsam fir regeneration, however, was not favored by PCT compared to the control. Our results show PCT increased tree size of individual aspen while promoting understory balsam fir growth in this type of stratified mixture. This approach should therefore be useful in limiting hardwood conversion in the boreal mixedwood forest at an early stage in stand development. Developing silvicultural approaches such as this one would be in line with the concept of ecosystem-based forest management.
Abstract
Collecting in situ gas-exchange measurements in canopies of mature trees is challenging, because the crown can be several meters above ground. Thus, we investigated the effect of detaching the leaf from the branch and time since detachment for three deciduous angiosperm species: black walnut (Juglans nigra), northern red oak (Quercus rubra), and white oak (Quercus alba). Results showed that net photosynthesis (A) was significantly reduced 3 min after leaf detachment in Quercus rubra, 6 min after leaf detachment in Q. alba, and 9 min after leaf detachment in J. nigra. Compared to the in situ measurement, a 72 ± 13% reduction (mean ± SE) in A occurred after 3 min in Q. rubra, a 74 ± 27% reduction in A occurred after 6 min in Q. alba, while a 41 ± 14% reduction in A occurred after 9 min in J. nigra. Furthermore, once the significant reduction in A occurred, it was maintained over the remaining time period for each species. Responses for stomatal conductance were similar to those of A. Results highlight the importance of measuring gas exchange in situ whenever possible. Otherwise, these results provide threshold time periods to carry out instantaneous gas-exchange measurements in the field for select hardwood species in which the canopy is difficult to access.
RÉSUMÉ
Nous avons utilisé les données de placettes permanentes établies pour suivre les effets de l'aménagement forestier dans des peuplements matures à dominance feuillue au Québec (Canada) dans le but de répondre à deux questions relatives à la mortalité des arbres : (1) Comment la coupe partielle affecte-t-elle le taux de mortalité des arbres? (2) Quelles variables expliquent le mieux la mortalité des arbres feuillus selon qu'ils sont morts sur pied, déracinés ou ont un tronc rompu? La mortalité décennale était moindre après une coupe partielle que dans les placettes non traitées, mais la proportion annuelle d'arbres morts était la même dans les deux (1,25 %·année-1). Parmi les variable étudiées, la classe de risque et de produit potentiel de l'arbre feuillu influençait le plus la probabilité globale de mortalité; elle était suivie par l' espèce, la présence d'une blessure de coupe, puis la dimension de l'arbre. La température annuelle était la seule variable climatique permettant d' expliquer la probabilité globale de mortalité des arbres, et l'une des trois variables les plus importantes pour les trois types de mort. Le risque de mourir sur pied augmentait aussi avec l'augmentation des précipitations annuelles, tandis que celui de rupture du tronc et, dans une moindre mesure, celui d' être déraciné diminuaient avec l'augmentation des précipitations. Finalement, nous avons observé que le risque de déracinement d'un arbre était influencé par le rapport potassium/magnésium dans la couche d'humus du sol. Ces informations sont importantes pour mieux comprendre les processus de mortalité des arbres.
birch and sugar maple, but further monitoring is required to determine its long-term efficacy.
this study examined juvenile (five growing seasons) morphological and physiological competitive aspects of American chestnut grown in a plantation setting with northern red oak (Quercus rubra L.) and black cherry (Prunus serotina Ehrh.) in Indiana, USA. Species were grown in seven possible species combinations including both monospecific and polyspecific combinations at three densities (1x1 m, 2x2 m, and
3x3 m). Despite an initial advantage in height, American chestnut exhibited the lowest relative height growth in the 2x2 and 3x3 m spacings, resulting in less total height compared to the other two species 5 years after planting. Relative height growth, as well as final absolute heights, were comparable among species in the 1x1 m spacing. Black cherry exhibited 2–3 times greater relative ground-line diameter (GLD) growth compared to oak and chestnut at all spacings. Linear regressions showed that growth
was generally proportional to net photosynthesis (A) for all species. Increases in A likely resulted from increases in leaf nitrogen concentration. Chestnut exhibited lower A than cherry and oak in years 2 and 3, but no differences occurred in year 4. Additionally, chestnut had significantly higher predawn leaf water potential (leaf Wpd) in year 4, reflecting greater drought stress in cherry and oak. While black cherry grew most aggressively, northern red oak and American chestnut performed acceptably, with high survival rates and moderate growth, especially in the 1x1 mspacing. American chestnut had the poorest stem form overall, but fared better in the 1x1 m spacing where the crown competition factor (CCF) was highest. Hence, an intermediate spacing between 1x1 and 2x2 m could optimize chestnut’s growth and stem form. Mixture effects may be attributed mainly to individual species growth characteristics rather than inter-specific interactions during this juvenile developmental stage.
• Aims: This study aims to (1) investigate walnut ecophysiology by comparing its attributes to associated deciduous angiosperms, (2) address potential acclimation of walnut to climate change, and (3) identify areas for prioritization in future research.
• Results: There is considerable uncertainty regarding the magnitude of potential effects of climate change on walnut. Some studies tend to indicate walnut could be negatively impacted by climate change, while others do not. Walnut may be at a disadvantage due to its susceptibility to drought and frost injury in current growing regions given the
projected increases in temperature and extreme climatic events. Other regions that are currently considered cold for walnut growth may see increased establishment and growth depending upon the rate of temperature increase and the frequency and severity of extreme climatic events.
• Conclusion: Research investigating a combination of environmental factors, such as temperature, carbon dioxide, ozone, water, and nitrogen is needed to (1) better project climate change effects on walnut and (2) develop management strategies for walnut acclimation and adaptation to climate change.
earlier, such as in June, may trigger a more rapid adaptation in A of thinned trees that was not detected in our
study.
unthinned control, PCT increased relative diameter increment of aspen saplings by 66–85% and relative basal area increment by 234–326%. Increases were similar among PCT treatments. Understory balsam fir regeneration >=1 m in height at time of thinning strongly benefited from PCT, with increases in height and crown width growth two to three times higher than in the control. The establishment of balsam fir regeneration, however, was not favored by PCT compared to the control. Our results show PCT increased tree size of individual aspen while promoting understory balsam fir growth in this type of stratified mixture. This approach should therefore be useful in limiting hardwood conversion in the boreal mixedwood forest at an early stage in stand development. Developing silvicultural approaches such as this one would be in line with the concept of ecosystem-based forest management.