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Yves Bergeron - One of the best experts on this subject based on the ideXlab platform.
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unexpected warming induced growth decline in Thuja occidentalis at its northern limits in north america
Journal of Biogeography, 2015Co-Authors: Johann M Housset, Yves Bergeron, Martin P Girardin, Mathieu Baconnet, Christopher CarcailletAbstract:Aim - Towards the cold margins of the Northern Hemisphere boreal zone, continuing warming should theoretically provide a longer vegetative season, favouring growth and a northward shift in tree species distribution. The north- ern distribution of Thuja occidentalis L. (eastern white cedar) is marked by the presence of isolated marginal populations distant from the continuous distribu- tion. If those populations proved to be well adapted to their future local cli- matic conditions, their expansion could accelerate cedar poleward migration. We tested the hypotheses that (1) there will be a growth increase in cedar northern marginal populations as a result of global warming, and (2) the edaphic conditions and regional precipitation regimes will modulate their response to warming. Location - Canadian boreal forest, western Quebec (47–50° N, 74–80° W). Methods - We investigated radial growth using tree-ring measurements from dominant and co-dominant eastern white cedar trees (n = 723) distributed along a latitudinal gradient from the species’ northern margin to the centre of its natural range. First, low-frequency growth variations were analysed on whole chronologies (ad 1720–2010). Second, inter-annual growth variations were tested against ad 1953–2010 monthly temperature and precipitation time series with a bootstrapped correlation function. Finally, the impact of environ- mental variables on the growth–climate relationships was assessed. Results - Unexpectedly, a growth decline was observed starting in 1980 in mar- ginal sites. Dendroclimatic analyses revealed that radial growth was not only limited by short growing seasons but also by summer droughts in the marginal zone. This response was exacerbated in sites that received less summer precipi- tation. Counterintuitively, autumn and spring precipitation negatively impacted on growth, especially in wet soil stands. Main conclusions - Northern marginal populations of cedar may have already reached their optimum temperature threshold for radial growth. Our results suggest that they will probably be facing increasing hydric stress selection pres- sure under the assumptions of climate change. Their responses to future warm- ing will be highly dependent on the seasonality and magnitude of variation in precipitation regimes.
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effects of biodegradation by brown rot decay on selected wood properties in eastern white cedar Thuja occidentalis l
International Biodeterioration & Biodegradation, 2014Co-Authors: Besma Bouslimi, Ahmed Koubaa, Yves BergeronAbstract:Abstract The effects of decay on wood density, wood structure, chemical composition, and mechanical properties in eastern white cedar (Thuja occidentalis L.) were investigated. Decay stage was determined by X-ray densitometry and scanning electron microscopy (SEM). Chemical and mechanical properties of decayed and sound wood samples were also determined. SEM results showed that decay colonization varied among wood cell types and within individual cell wall layers. Growth of fungi causing brown rot decay was limited and slower in latewood than in earlywood due to the narrow cell lumen, thicker wall, and higher density of latewood. Decay-related changes in wood density were more prominent in earlywood than latewood tracheids. Brown-rot decay selectively removes structural carbohydrate components, increasing the higher lignin/carbohydrate ratio as decay progresses. The relationships between chemical composition, mechanical properties, and weight loss were highly significant, with 15% weight loss leading to 40% loss in modulus of rupture (MOR) and 30% loss in bending modulus of elasticity (MOE). The strength loss (MOR) was attributable to arabinan and galactan loss. The loss in wood stiffness was associated with cellulose (glucan) loss, and weight loss was associated with mannan and xylans losses.
Peter B. Reich - One of the best experts on this subject based on the ideXlab platform.
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Comparing the Importance of Seedbed and Canopy Type in the Restoration of Upland Thuja occidentalis Forests of Northeastern Minnesota
Restoration Ecology, 2001Co-Authors: Meredith W. Cornett, Klaus J. Puettmann, Lee E. Frelich, Peter B. ReichAbstract:In cold-temperate ecosystems of the upper Great Lakes Region, evergreen conifer-dominated forests were once common. As a result of past management practices, early-successional deciduous forests now dominate the landscape. Embedded in this matrix are stands of shade-tolerant conifers, including Thuja occidentalis . For the past several decades, large-scale T. occidentalis regeneration in remnant T. occidentalis and adjacent Betula papyrifera forests has not occurred. Using a combination of restoration experiments and field surveys at three study sites on the Lake Superior Highlands, Minnesota, U.S.A., we examined safe sites for T. occidentalis regeneration under both Thuja and Betula canopy types. This study focused on the colonization and establishment phases of regeneration, differentiating among safe-site components for T. occidentalis . Seedbed type determined colonization success, with higher rates on conifer logs than on B. papyrifera logs, mounds, or pits. Mortality rates for seedlings on natural decayed wood seedbeds were higher under Thuja canopy than under Betula canopy, but the reverse was true for seedlings on manipulated seedbeds, suggesting that seedbed type was more important than the dominant canopy type. Growth rates for seedlings on moved log segments were greater under the Betula than the Thuja canopy type, but seedlings on natural decayed wood seedbeds did not exhibit this difference. Results indicated that T. occidentalis regeneration was more limited in Betula forest by seedbed availability, while in Thuja forest canopy conditions were more limiting.
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Seedbed and moisture availability determine safe sites for early Thuja occidentalis (Cupressaceae) regeneration.
American journal of botany, 2000Co-Authors: Meredith W. Cornett, Peter B. Reich, Klaus J. Puettmann, Lee E. FrelichAbstract:Regeneration of many late-successional tree species depends on specialized safe sites. The primary objective was to investigate the roles of seedbed and moisture retention as dimensions of safe sites for the early regeneration of drought-sensitive northern white cedar (Thuja occidentalis). We hypothesized that rates of germination, survival, and growth of T. occidentalis are unlikely to differ among seedbed types under conditions of abundant water, but that differences are likely to emerge as water becomes more limited. In a 67d greenhouse experiment, cedar seeds were sown on logs, leaf litter, and soil of cedar and paper birch (Betula papyrifera) canopy origin. Seedbeds were subjected to three water treatments. Among the water treatments, highest germination rates occurred within the high water treatment, although germination on cedar litter was comparable to that of the low water treatment. Higher germination and survival rates occurred on decayed logs than other natural seedbeds for medium (P 5 0.001) and low (P , 0.0001) water treatments. Germination on birch logs occurred at higher rates than on cedar logs within the low water treatment (P 5 0.04). Seedling growth for the medium water treatment was lower on leaf litter than any other type of seedbed (P , 0.01). Results generally demonstrated that the interplay between seedbed and moisture retention is a component of safe sites for T. occidentalis regeneration.
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conservation implications of browsing by odocoileus virginianus in remnant upland Thuja occidentalis forests
Biological Conservation, 2000Co-Authors: Meredith W. Cornett, Klaus J. Puettmann, Lee E. Frelich, Peter B. ReichAbstract:Regeneration success of canopy dominants is linked to multiple factors, including the ability of their seedlings to survive browsing and to utilize available resources in the understory. In remnant upland northern white cedar Thuja occidentalis L. forests, eAects of browsing on recruitment of cedar seedlings were evaluated at 7 sites, including known deer yards, located on a portion of the Lake Superior Highlands in northeastern Minnesota. Experimental plantings and vegetation surveys were conducted inside and outside large deer exclosures constructed between 1937 and 1997. Objectives were to determine severity and intensity of browsing by Odocoileus virginianus Zimmerman, the ability of seedlings to survive browsing in environments beneath T. occidentalis and adjacent paper birch (Betula papyrifera) Marshall canopies, and potential long-term sapling recruitment under diAerent browsing scenarios. From 1994 to 1997, 76% of unexclosed planted T. occidentalis seedlings had been browsed at least once, compared with 0% of exclosed seedlings. Increased browsing intensity and decreased light availability increased T. occidentalis mortality rates. Simulation models and vegetation surveys demonstrated that the best recruitment rates occurred for seedlings planted under Betula canopy and subjected to low browsing severity, but no recruitment occurred under high browsing pressure under either canopy type. The current level of browsing in these forests has the potential to alter the future composition of canopy tree species through sustained prevention of T. occidentalis recruitment. # 2000 Published by Elsevier Science Ltd. All rights reserved.
Om P Rajora - One of the best experts on this subject based on the ideXlab platform.
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higher fine scale genetic structure in peripheral than in core populations of a long lived and mixed mating conifer eastern white cedar Thuja occidentalis l
BMC Evolutionary Biology, 2012Co-Authors: Madhav Pandey, Om P RajoraAbstract:Fine-scale or spatial genetic structure (SGS) is one of the key genetic characteristics of plant populations. Several evolutionary and ecological processes and population characteristics influence the level of SGS within plant populations. Higher fine-scale genetic structure may be expected in peripheral than core populations of long-lived forest trees, owing to the differences in the magnitude of operating evolutionary and ecological forces such as gene flow, genetic drift, effective population size and founder effects. We addressed this question using eastern white cedar (Thuja occidentalis) as a model species for declining to endangered long-lived tree species with mixed-mating system. We determined the SGS in two core and two peripheral populations of eastern white cedar from its Maritime Canadian eastern range using six nuclear microsatellite DNA markers. Significant SGS ranging from 15 m to 75 m distance classes was observed in the four studied populations. An analysis of combined four populations revealed significant positive SGS up to the 45 m distance class. The mean positive significant SGS observed in the peripheral populations was up to six times (up to 90 m) of that observed in the core populations (15 m). Spatial autocorrelation coefficients and correlograms of single and sub-sets of populations were statistically significant. The extent of within-population SGS was significantly negatively correlated with all genetic diversity parameters. Significant heterogeneity of within-population SGS was observed for 0-15 m and 61-90 m between core and peripheral populations. Average Sp, and gene flow distances were higher in peripheral (Sp = 0.023, σg = 135 m) than in core (Sp = 0.014, σg = 109 m) populations. However, the mean neighborhood size was higher in the core (Nb = 82) than in the peripheral (Nb = 48) populations. Eastern white cedar populations have significant fine-scale genetic structure at short distances. Peripheral populations have several-folds higher within-population fine-scale genetic structure than core populations. Anthropogenic disturbances and population fragmentation presumably have significant effects on fine-scale genetic structure in eastern white cedar. Core populations have higher neighborhood size than peripheral populations, whereas gene flow distances are higher in peripheral than in core populations. The results of our study contribute to the knowledge of poorly-understood spatial genetic structure of core versus peripheral populations in plants. As well, the information is of significance for conservation of genetic resources of eastern white cedar and perhaps of other long-lived forest trees with mixed-mating system.
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genetic diversity and differentiation of core vs peripheral populations of eastern white cedar Thuja occidentalis cupressaceae
American Journal of Botany, 2012Co-Authors: Madhav Pandey, Om P RajoraAbstract:PREMISE OF THE STUDY Geographically peripheral (marginal) populations are expected to have lower genetic diversity and higher genetic differentiation than geographically core (central) populations as a result of supposedly lower effective population size (N(e)) and higher genetic drift, founder effect, fragmentation, and isolation in peripheral than in core populations. Here we address this issue for a long-lived plant species, eastern white cedar (Thuja occidentalis). METHODS Genetic diversity and population structure of 13 natural populations of eastern white cedar from its Canadian eastern peripheral and core natural ranges in New Brunswick, Nova Scotia, and Prince Edward Island were studied using six nuclear microsatellite DNA markers. KEY RESULTS The core populations of eastern white cedar had significantly higher allelic diversity (mean A = 8.83, A(r) = 8.13, A(e) = 4.03) and N(e) (428) than the peripheral populations (A = 6.64, A(r) = 6.15, A(e) = 3.12, N(e) = 198). However, expected heterozygosity was similar in the core (H(e) = 0.64) and peripheral (H(e) = 0.60) populations. Genetic differentiation was significantly higher among the peripheral (F(ST) = 0.089) than among the core (F(ST) = 0.032) populations. No genetic differentiation (F(ST)/Φ(RT) = 0.000) was detected between core and peripheral regions. CONCLUSIONS Peripheral populations have significantly lower N(e) and genetic diversity in terms of allelic diversity (richness) and significantly higher genetic differentiation than the core populations of eastern white cedar in its Canadian eastern range. However, core and peripheral populations have similar levels of expected heterozygosity. Implications for conservation of eastern white cedar genetic resources are discussed.
Madhav Pandey - One of the best experts on this subject based on the ideXlab platform.
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higher fine scale genetic structure in peripheral than in core populations of a long lived and mixed mating conifer eastern white cedar Thuja occidentalis l
BMC Evolutionary Biology, 2012Co-Authors: Madhav Pandey, Om P RajoraAbstract:Fine-scale or spatial genetic structure (SGS) is one of the key genetic characteristics of plant populations. Several evolutionary and ecological processes and population characteristics influence the level of SGS within plant populations. Higher fine-scale genetic structure may be expected in peripheral than core populations of long-lived forest trees, owing to the differences in the magnitude of operating evolutionary and ecological forces such as gene flow, genetic drift, effective population size and founder effects. We addressed this question using eastern white cedar (Thuja occidentalis) as a model species for declining to endangered long-lived tree species with mixed-mating system. We determined the SGS in two core and two peripheral populations of eastern white cedar from its Maritime Canadian eastern range using six nuclear microsatellite DNA markers. Significant SGS ranging from 15 m to 75 m distance classes was observed in the four studied populations. An analysis of combined four populations revealed significant positive SGS up to the 45 m distance class. The mean positive significant SGS observed in the peripheral populations was up to six times (up to 90 m) of that observed in the core populations (15 m). Spatial autocorrelation coefficients and correlograms of single and sub-sets of populations were statistically significant. The extent of within-population SGS was significantly negatively correlated with all genetic diversity parameters. Significant heterogeneity of within-population SGS was observed for 0-15 m and 61-90 m between core and peripheral populations. Average Sp, and gene flow distances were higher in peripheral (Sp = 0.023, σg = 135 m) than in core (Sp = 0.014, σg = 109 m) populations. However, the mean neighborhood size was higher in the core (Nb = 82) than in the peripheral (Nb = 48) populations. Eastern white cedar populations have significant fine-scale genetic structure at short distances. Peripheral populations have several-folds higher within-population fine-scale genetic structure than core populations. Anthropogenic disturbances and population fragmentation presumably have significant effects on fine-scale genetic structure in eastern white cedar. Core populations have higher neighborhood size than peripheral populations, whereas gene flow distances are higher in peripheral than in core populations. The results of our study contribute to the knowledge of poorly-understood spatial genetic structure of core versus peripheral populations in plants. As well, the information is of significance for conservation of genetic resources of eastern white cedar and perhaps of other long-lived forest trees with mixed-mating system.
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genetic diversity and differentiation of core vs peripheral populations of eastern white cedar Thuja occidentalis cupressaceae
American Journal of Botany, 2012Co-Authors: Madhav Pandey, Om P RajoraAbstract:PREMISE OF THE STUDY Geographically peripheral (marginal) populations are expected to have lower genetic diversity and higher genetic differentiation than geographically core (central) populations as a result of supposedly lower effective population size (N(e)) and higher genetic drift, founder effect, fragmentation, and isolation in peripheral than in core populations. Here we address this issue for a long-lived plant species, eastern white cedar (Thuja occidentalis). METHODS Genetic diversity and population structure of 13 natural populations of eastern white cedar from its Canadian eastern peripheral and core natural ranges in New Brunswick, Nova Scotia, and Prince Edward Island were studied using six nuclear microsatellite DNA markers. KEY RESULTS The core populations of eastern white cedar had significantly higher allelic diversity (mean A = 8.83, A(r) = 8.13, A(e) = 4.03) and N(e) (428) than the peripheral populations (A = 6.64, A(r) = 6.15, A(e) = 3.12, N(e) = 198). However, expected heterozygosity was similar in the core (H(e) = 0.64) and peripheral (H(e) = 0.60) populations. Genetic differentiation was significantly higher among the peripheral (F(ST) = 0.089) than among the core (F(ST) = 0.032) populations. No genetic differentiation (F(ST)/Φ(RT) = 0.000) was detected between core and peripheral regions. CONCLUSIONS Peripheral populations have significantly lower N(e) and genetic diversity in terms of allelic diversity (richness) and significantly higher genetic differentiation than the core populations of eastern white cedar in its Canadian eastern range. However, core and peripheral populations have similar levels of expected heterozygosity. Implications for conservation of eastern white cedar genetic resources are discussed.
Meredith W. Cornett - One of the best experts on this subject based on the ideXlab platform.
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Comparing the Importance of Seedbed and Canopy Type in the Restoration of Upland Thuja occidentalis Forests of Northeastern Minnesota
Restoration Ecology, 2001Co-Authors: Meredith W. Cornett, Klaus J. Puettmann, Lee E. Frelich, Peter B. ReichAbstract:In cold-temperate ecosystems of the upper Great Lakes Region, evergreen conifer-dominated forests were once common. As a result of past management practices, early-successional deciduous forests now dominate the landscape. Embedded in this matrix are stands of shade-tolerant conifers, including Thuja occidentalis . For the past several decades, large-scale T. occidentalis regeneration in remnant T. occidentalis and adjacent Betula papyrifera forests has not occurred. Using a combination of restoration experiments and field surveys at three study sites on the Lake Superior Highlands, Minnesota, U.S.A., we examined safe sites for T. occidentalis regeneration under both Thuja and Betula canopy types. This study focused on the colonization and establishment phases of regeneration, differentiating among safe-site components for T. occidentalis . Seedbed type determined colonization success, with higher rates on conifer logs than on B. papyrifera logs, mounds, or pits. Mortality rates for seedlings on natural decayed wood seedbeds were higher under Thuja canopy than under Betula canopy, but the reverse was true for seedlings on manipulated seedbeds, suggesting that seedbed type was more important than the dominant canopy type. Growth rates for seedlings on moved log segments were greater under the Betula than the Thuja canopy type, but seedlings on natural decayed wood seedbeds did not exhibit this difference. Results indicated that T. occidentalis regeneration was more limited in Betula forest by seedbed availability, while in Thuja forest canopy conditions were more limiting.
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Seedbed and moisture availability determine safe sites for early Thuja occidentalis (Cupressaceae) regeneration.
American journal of botany, 2000Co-Authors: Meredith W. Cornett, Peter B. Reich, Klaus J. Puettmann, Lee E. FrelichAbstract:Regeneration of many late-successional tree species depends on specialized safe sites. The primary objective was to investigate the roles of seedbed and moisture retention as dimensions of safe sites for the early regeneration of drought-sensitive northern white cedar (Thuja occidentalis). We hypothesized that rates of germination, survival, and growth of T. occidentalis are unlikely to differ among seedbed types under conditions of abundant water, but that differences are likely to emerge as water becomes more limited. In a 67d greenhouse experiment, cedar seeds were sown on logs, leaf litter, and soil of cedar and paper birch (Betula papyrifera) canopy origin. Seedbeds were subjected to three water treatments. Among the water treatments, highest germination rates occurred within the high water treatment, although germination on cedar litter was comparable to that of the low water treatment. Higher germination and survival rates occurred on decayed logs than other natural seedbeds for medium (P 5 0.001) and low (P , 0.0001) water treatments. Germination on birch logs occurred at higher rates than on cedar logs within the low water treatment (P 5 0.04). Seedling growth for the medium water treatment was lower on leaf litter than any other type of seedbed (P , 0.01). Results generally demonstrated that the interplay between seedbed and moisture retention is a component of safe sites for T. occidentalis regeneration.
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conservation implications of browsing by odocoileus virginianus in remnant upland Thuja occidentalis forests
Biological Conservation, 2000Co-Authors: Meredith W. Cornett, Klaus J. Puettmann, Lee E. Frelich, Peter B. ReichAbstract:Regeneration success of canopy dominants is linked to multiple factors, including the ability of their seedlings to survive browsing and to utilize available resources in the understory. In remnant upland northern white cedar Thuja occidentalis L. forests, eAects of browsing on recruitment of cedar seedlings were evaluated at 7 sites, including known deer yards, located on a portion of the Lake Superior Highlands in northeastern Minnesota. Experimental plantings and vegetation surveys were conducted inside and outside large deer exclosures constructed between 1937 and 1997. Objectives were to determine severity and intensity of browsing by Odocoileus virginianus Zimmerman, the ability of seedlings to survive browsing in environments beneath T. occidentalis and adjacent paper birch (Betula papyrifera) Marshall canopies, and potential long-term sapling recruitment under diAerent browsing scenarios. From 1994 to 1997, 76% of unexclosed planted T. occidentalis seedlings had been browsed at least once, compared with 0% of exclosed seedlings. Increased browsing intensity and decreased light availability increased T. occidentalis mortality rates. Simulation models and vegetation surveys demonstrated that the best recruitment rates occurred for seedlings planted under Betula canopy and subjected to low browsing severity, but no recruitment occurred under high browsing pressure under either canopy type. The current level of browsing in these forests has the potential to alter the future composition of canopy tree species through sustained prevention of T. occidentalis recruitment. # 2000 Published by Elsevier Science Ltd. All rights reserved.