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Eric Dufrêne - One of the best experts on this subject based on the ideXlab platform.
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comparing the intra annual wood formation of three european species fagus sylvatica Quercus Petraea and pinus sylvestris as related to leaf phenology and non structural carbohydrate dynamics
Tree Physiology, 2012Co-Authors: Eric Dufrêne, Alice Michelot, Claire Damesin, Sonia Simard, Cyrille B K RathgeberAbstract:Monitoring cambial phenology and intra-annual growth dynamics is a useful approach for characterizing the tree growth response to climate change. However, there have been few reports concerning intra-annual wood formation in lowland temperate forests with high time resolution, especially for the comparison between deciduous and coniferous species. The main objective of this study was to determine how the timing, duration and rate of radial growth change between species as related to leaf phenology and the dynamics of non-structural carbohydrates (NSC) under the same climatic conditions. We studied two deciduous species, Fagus sylvatica L. and Quercus Petraea (Matt.) Liebl., and an evergreen conifer, Pinus sylvestris L. During the 2009 growing season, we weekly monitored (i) the stem radial increment using dendrometers, (ii) the xylem growth using microcoring and (iii) the leaf phenology from direct observations of the tree crowns. The NSC content was also measured in the eight last rings of the stem cores in April, June and August 2009. The leaf phenology, NSC storage and intra-annual growth were clearly different between species, highlighting their contrasting carbon allocation. Beech growth began just after budburst, with a maximal growth rate when the leaves were mature and variations in the NSC content were low. Thus, beech radial growth seemed highly dependent on leaf photosynthesis. For oak, earlywood quickly developed before budburst, which probably led to the starch decrease quantified in the stem from April to June. For pine, growth began before the needles unfolding and the lack of NSC decrease during the growing season suggested that the substrates for radial growth were new assimilates of the needles from the previous year. Only for oak, the pattern determined from the intra-annual growth measured using microcoring differed from the pattern determined from dendrometer data. For all species, the ring width was significantly influenced by growth duration and not by growth rate, which differs from previous studies. The observed between-species difference at the intra-annual scale is key information for anticipating suitability of future species in temperate forests.
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differing growth responses to climatic variations and soil water deficits of fagus sylvatica Quercus Petraea and pinus sylvestris in a temperate forest
Forest Ecology and Management, 2012Co-Authors: Nathalie Bréda, Eric Dufrêne, Alice Michelot, Claire DamesinAbstract:Abstract In addition to global warming, the frequency and the intensity of droughts will probably increase in central and southern Europe. Resulting climate changes and soil water deficits could alter tree growth, according to sensitivity of each species. The aim of this study was to compare the growth response of three European species (Fagus sylvatica, Quercus Petraea and Pinus sylvestris) to climatic variations and soil water deficits in the same temperate forest. Three mature stands per species were sampled to obtain earlywood, latewood and total ring chronologies from 1960 to 2007. Climate–growth relationships were established by bootstrapped correlations and response function analysis. Monthly bioclimatic regressors were simulated by a physiological water balance model that used daily climatic data and stand parameters to estimate soil water deficits. Our results highlighted a common sensitivity to precipitation from May to July for the dominant tree growth of the three species but also differences in the species vulnerability to climate and soil water deficits. Beech was the most sensitive species to the climatic conditions of the current growing season. Beech growth was positively correlated with precipitation from May to July and negatively with maximal temperatures in June and July. Oak growth was negatively correlated with minimal temperatures in the previous August and September and positively with precipitation in the previous October and December during pointer years. This led to long-term consequences for growth, probably due to carbon reserve depletion. Pine growth was positively influenced by warm December but was also vulnerable to maximal temperatures and soil water deficits from June to August. The climate in August only influenced the pine growth probably because the growing season of pine was longer than that of the deciduous species. For both oak and pine, latewood was the component that was most sensitive to climatic variations and soil water deficits. According to the study findings, an increase in the frequency and the intensity of droughts could affect the three species. Maximum summer temperatures could have negative impacts for beech and pine growth. Dry and warm autumns could lead to long-term consequences and decrease the oak growth.
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age related variation in carbon allocation at tree and stand scales in beech fagus sylvatica l and sessile oak Quercus Petraea matt liebl using a chronosequence approach
Tree Physiology, 2010Co-Authors: Helene Genet, Nathalie Bréda, Eric DufrêneAbstract:Two types of physiological mechanisms can contribute to growth decline with age: (i) the mechanisms leading to the reduction of carbon assimilation (input) and (ii) those leading to modification of the resource economy. Surprisingly, the processes relating to carbon allocation have been little investigated as compared to research on the processes governing carbon assimilation. The objective of this paper was thus to test the hypothesis that growth decrease related to age is accompanied by changes in carbon allocation to the benefit of storage and reproductive functions in two contrasting broad-leaved species: beech (Fagus sylvatica L.) and sessile oak (Quercus Petraea (Matt.) Liebl.). Age-related changes in carbon allocation were studied using a chronosequence approach. Chronosequences, each consisting of several even-aged stands ranging from 14 to 175 years old for beech and from 30 to 134 years old for sessile oak, were divided into five or six age classes. In this study, carbon allocations to growth, storage and reproduction were defined as the relative amount of carbon invested in biomass increment, carbohydrate increment and seed production, respectively. Tree-ring width and allometric relationships were used to assess biomass increment at the tree and stand scales. Below-ground biomass was assessed using a specific allometric relationship between root:shoot ratio and age, established from the literature review. Seasonal variations of carbohydrate concentrations were used to assess carbon allocation to storage. Reproduction effort was quantified for beech stands by collecting seed and cupule production. Age-related flagging of biomass productivity was assessed at the tree and stand scales, and carbohydrate quantities in trees increased with age for both species. Seed and cupule production increased with stand age in beech from 56 gC m(-)(2) year(-1) at 30 years old to 129 gC m(-2) year(-1) at 138 years old. In beech, carbon allocation to storage and reproductive functions increased with age to the detriment of carbon allocation to growth functions. In contrast, the carbon balance between growth and storage remained constant between age classes in sessile oak. The contrasting age-related changes in carbon allocation between beech and sessile oak are discussed with reference to the differences in growing environment, phenology and hydraulic properties of ring-porous and diffuse-porous species.
Nathalie Bréda - One of the best experts on this subject based on the ideXlab platform.
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differing growth responses to climatic variations and soil water deficits of fagus sylvatica Quercus Petraea and pinus sylvestris in a temperate forest
Forest Ecology and Management, 2012Co-Authors: Nathalie Bréda, Eric Dufrêne, Alice Michelot, Claire DamesinAbstract:Abstract In addition to global warming, the frequency and the intensity of droughts will probably increase in central and southern Europe. Resulting climate changes and soil water deficits could alter tree growth, according to sensitivity of each species. The aim of this study was to compare the growth response of three European species (Fagus sylvatica, Quercus Petraea and Pinus sylvestris) to climatic variations and soil water deficits in the same temperate forest. Three mature stands per species were sampled to obtain earlywood, latewood and total ring chronologies from 1960 to 2007. Climate–growth relationships were established by bootstrapped correlations and response function analysis. Monthly bioclimatic regressors were simulated by a physiological water balance model that used daily climatic data and stand parameters to estimate soil water deficits. Our results highlighted a common sensitivity to precipitation from May to July for the dominant tree growth of the three species but also differences in the species vulnerability to climate and soil water deficits. Beech was the most sensitive species to the climatic conditions of the current growing season. Beech growth was positively correlated with precipitation from May to July and negatively with maximal temperatures in June and July. Oak growth was negatively correlated with minimal temperatures in the previous August and September and positively with precipitation in the previous October and December during pointer years. This led to long-term consequences for growth, probably due to carbon reserve depletion. Pine growth was positively influenced by warm December but was also vulnerable to maximal temperatures and soil water deficits from June to August. The climate in August only influenced the pine growth probably because the growing season of pine was longer than that of the deciduous species. For both oak and pine, latewood was the component that was most sensitive to climatic variations and soil water deficits. According to the study findings, an increase in the frequency and the intensity of droughts could affect the three species. Maximum summer temperatures could have negative impacts for beech and pine growth. Dry and warm autumns could lead to long-term consequences and decrease the oak growth.
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age related variation in carbon allocation at tree and stand scales in beech fagus sylvatica l and sessile oak Quercus Petraea matt liebl using a chronosequence approach
Tree Physiology, 2010Co-Authors: Helene Genet, Nathalie Bréda, Eric DufrêneAbstract:Two types of physiological mechanisms can contribute to growth decline with age: (i) the mechanisms leading to the reduction of carbon assimilation (input) and (ii) those leading to modification of the resource economy. Surprisingly, the processes relating to carbon allocation have been little investigated as compared to research on the processes governing carbon assimilation. The objective of this paper was thus to test the hypothesis that growth decrease related to age is accompanied by changes in carbon allocation to the benefit of storage and reproductive functions in two contrasting broad-leaved species: beech (Fagus sylvatica L.) and sessile oak (Quercus Petraea (Matt.) Liebl.). Age-related changes in carbon allocation were studied using a chronosequence approach. Chronosequences, each consisting of several even-aged stands ranging from 14 to 175 years old for beech and from 30 to 134 years old for sessile oak, were divided into five or six age classes. In this study, carbon allocations to growth, storage and reproduction were defined as the relative amount of carbon invested in biomass increment, carbohydrate increment and seed production, respectively. Tree-ring width and allometric relationships were used to assess biomass increment at the tree and stand scales. Below-ground biomass was assessed using a specific allometric relationship between root:shoot ratio and age, established from the literature review. Seasonal variations of carbohydrate concentrations were used to assess carbon allocation to storage. Reproduction effort was quantified for beech stands by collecting seed and cupule production. Age-related flagging of biomass productivity was assessed at the tree and stand scales, and carbohydrate quantities in trees increased with age for both species. Seed and cupule production increased with stand age in beech from 56 gC m(-)(2) year(-1) at 30 years old to 129 gC m(-2) year(-1) at 138 years old. In beech, carbon allocation to storage and reproductive functions increased with age to the detriment of carbon allocation to growth functions. In contrast, the carbon balance between growth and storage remained constant between age classes in sessile oak. The contrasting age-related changes in carbon allocation between beech and sessile oak are discussed with reference to the differences in growing environment, phenology and hydraulic properties of ring-porous and diffuse-porous species.
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Carbon isotope discrimination and wood anatomy variations in mixed stands of Quercus robur and Quercus Petraea
Plant Cell & Environment, 2001Co-Authors: Stéphane Ponton, Jean-luc Dupouey, Nathalie Bréda, F. Feuillat, Catherine Bodénès, Erwin DreyerAbstract:The two most common oak species in western Europe, Quercus robur and Quercus Petraea, display different ecological behaviours, particularly with respect to their responses to drought. The ecophysiological basis of this niche difference is not understood well. Here we test the hypothesis that these two species present distinct water use efficiencies (WUEs), using the carbon isotope discrimination approach. Leaves and 13 dated ring sequences were sampled in 10 pairs of adult trees growing side by side. Carbon isotope composition was measured on cellulose extracts. In addition, relationships between carbon isotope discrimination and wood anatomy were assessed at the tree level. Quercus robur displayed a 1.0‰ larger isotopic discrimination than Q. Petraea, and therefore a lower intrinsic WUE (-13%). This interspecific difference of isotopic discrimination was quite stable with time and independent of tree radial growth and climate fluctuations. A strong positive correlation was observed between average tree values of earlywood vessel surface area and 13 C isotopic discrimination. This correlation was even higher with 13 C of the 1976 dry year (r = 0.86). These observations led to the hypothesis that hydraulic properties of xylem could exert a constraint on leaf gas exchange, resulting in a larger WUE for individuals with smaller vessel cross-section area.
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effects of thinning on soil and tree water relations transpiration and growth in an oak forest Quercus Petraea matt liebl
Tree Physiology, 1995Co-Authors: Nathalie Bréda, A Granier, G AussenacAbstract:Summary To quantify the effects of crown thinning on the water balance and growth of the stand and to analyze the ecophysiological modifications induced by canopy opening on individual tree water relations, we conducted a thinning experi ment in a 43-year-old Quercus Petraea stand by removing trees from the upper canopy level. Soil water content, rainfall inter ception, sap flow, leaf water potential and stomatal conduc tance were monitored for two seasons following thinning. Seasonal time courses of leaf area index (LAI) and girth increment were also measured. Predawn leaf water potential was significantly higher in trees in the thinned stand than in the closed stand, as a conse quence of higher relative extractable water in the soil. The improvement in water availability in the thinned stand resulted from decreases in both interception and transpiration. From Year 1 to Year 2, an increase in transpiration was observed in the thinned stand without any modification in LAI, whereas changes in transpiration in the closed stand were accompanied by variations in LAI. The different behaviors of the closed and open canopies were interpreted in terms of coupling to the atmosphere. Thinning increased inter-tree variability in sap flow density, which was closely related to a leaf area competi tion index. Stomatal conductance varied little inside the crown and differences in stomatal conductance between the treat ments appeared only during a water shortage and affected mainly the closed stand. Thinning enhanced tree growth as a result of a longer growing period due to the absence of summer drought and higher rates of growth. Suppressed and dominant trees benefited more from thinning than trees in the codomi nant classes.
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field comparison of transpiration stomatal conductance and vulnerability to cavitation of Quercus Petraea and Quercus robur under water stress
Annals of Forest Science, 1993Co-Authors: Nathalie Bréda, Erwin Dreyer, Herve Cochard, Agnes GranierAbstract:in adult oaks (Quercus Petraea and Q robur) during a period of water shortage in a simplified lysimeter. Sap flux densities and stomatal conductance were reduced by = 70% at maximal drought intensity. Predawn leaf water potential then ranged from -1.7 to -2.0 MPa. The slightly lower transpiration observed in pedunculate oaks could be ascribed to their smaller crown development. Nevertheless, no significant difference in stomatal conductance could be observed between the two species. They also had the same percent loss of conductivity (= 80%) in petioles at maximal drought intensity when midday leaf water potential had dropped to = -3.0 MPa. Finally, good agreement was found between observed losses of hydraulic conductivity during in situ dehydration and the vulnerability curves obtained under laboratory conditions. The shifts in maximal conductivity observed in some droughted trees probably accentuated discrepancies between field and laboratory data. However, a correction procedure helped overcome these artifacts.
Claire Damesin - One of the best experts on this subject based on the ideXlab platform.
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comparing the intra annual wood formation of three european species fagus sylvatica Quercus Petraea and pinus sylvestris as related to leaf phenology and non structural carbohydrate dynamics
Tree Physiology, 2012Co-Authors: Eric Dufrêne, Alice Michelot, Claire Damesin, Sonia Simard, Cyrille B K RathgeberAbstract:Monitoring cambial phenology and intra-annual growth dynamics is a useful approach for characterizing the tree growth response to climate change. However, there have been few reports concerning intra-annual wood formation in lowland temperate forests with high time resolution, especially for the comparison between deciduous and coniferous species. The main objective of this study was to determine how the timing, duration and rate of radial growth change between species as related to leaf phenology and the dynamics of non-structural carbohydrates (NSC) under the same climatic conditions. We studied two deciduous species, Fagus sylvatica L. and Quercus Petraea (Matt.) Liebl., and an evergreen conifer, Pinus sylvestris L. During the 2009 growing season, we weekly monitored (i) the stem radial increment using dendrometers, (ii) the xylem growth using microcoring and (iii) the leaf phenology from direct observations of the tree crowns. The NSC content was also measured in the eight last rings of the stem cores in April, June and August 2009. The leaf phenology, NSC storage and intra-annual growth were clearly different between species, highlighting their contrasting carbon allocation. Beech growth began just after budburst, with a maximal growth rate when the leaves were mature and variations in the NSC content were low. Thus, beech radial growth seemed highly dependent on leaf photosynthesis. For oak, earlywood quickly developed before budburst, which probably led to the starch decrease quantified in the stem from April to June. For pine, growth began before the needles unfolding and the lack of NSC decrease during the growing season suggested that the substrates for radial growth were new assimilates of the needles from the previous year. Only for oak, the pattern determined from the intra-annual growth measured using microcoring differed from the pattern determined from dendrometer data. For all species, the ring width was significantly influenced by growth duration and not by growth rate, which differs from previous studies. The observed between-species difference at the intra-annual scale is key information for anticipating suitability of future species in temperate forests.
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differing growth responses to climatic variations and soil water deficits of fagus sylvatica Quercus Petraea and pinus sylvestris in a temperate forest
Forest Ecology and Management, 2012Co-Authors: Nathalie Bréda, Eric Dufrêne, Alice Michelot, Claire DamesinAbstract:Abstract In addition to global warming, the frequency and the intensity of droughts will probably increase in central and southern Europe. Resulting climate changes and soil water deficits could alter tree growth, according to sensitivity of each species. The aim of this study was to compare the growth response of three European species (Fagus sylvatica, Quercus Petraea and Pinus sylvestris) to climatic variations and soil water deficits in the same temperate forest. Three mature stands per species were sampled to obtain earlywood, latewood and total ring chronologies from 1960 to 2007. Climate–growth relationships were established by bootstrapped correlations and response function analysis. Monthly bioclimatic regressors were simulated by a physiological water balance model that used daily climatic data and stand parameters to estimate soil water deficits. Our results highlighted a common sensitivity to precipitation from May to July for the dominant tree growth of the three species but also differences in the species vulnerability to climate and soil water deficits. Beech was the most sensitive species to the climatic conditions of the current growing season. Beech growth was positively correlated with precipitation from May to July and negatively with maximal temperatures in June and July. Oak growth was negatively correlated with minimal temperatures in the previous August and September and positively with precipitation in the previous October and December during pointer years. This led to long-term consequences for growth, probably due to carbon reserve depletion. Pine growth was positively influenced by warm December but was also vulnerable to maximal temperatures and soil water deficits from June to August. The climate in August only influenced the pine growth probably because the growing season of pine was longer than that of the deciduous species. For both oak and pine, latewood was the component that was most sensitive to climatic variations and soil water deficits. According to the study findings, an increase in the frequency and the intensity of droughts could affect the three species. Maximum summer temperatures could have negative impacts for beech and pine growth. Dry and warm autumns could lead to long-term consequences and decrease the oak growth.
Alice Michelot - One of the best experts on this subject based on the ideXlab platform.
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comparing the intra annual wood formation of three european species fagus sylvatica Quercus Petraea and pinus sylvestris as related to leaf phenology and non structural carbohydrate dynamics
Tree Physiology, 2012Co-Authors: Eric Dufrêne, Alice Michelot, Claire Damesin, Sonia Simard, Cyrille B K RathgeberAbstract:Monitoring cambial phenology and intra-annual growth dynamics is a useful approach for characterizing the tree growth response to climate change. However, there have been few reports concerning intra-annual wood formation in lowland temperate forests with high time resolution, especially for the comparison between deciduous and coniferous species. The main objective of this study was to determine how the timing, duration and rate of radial growth change between species as related to leaf phenology and the dynamics of non-structural carbohydrates (NSC) under the same climatic conditions. We studied two deciduous species, Fagus sylvatica L. and Quercus Petraea (Matt.) Liebl., and an evergreen conifer, Pinus sylvestris L. During the 2009 growing season, we weekly monitored (i) the stem radial increment using dendrometers, (ii) the xylem growth using microcoring and (iii) the leaf phenology from direct observations of the tree crowns. The NSC content was also measured in the eight last rings of the stem cores in April, June and August 2009. The leaf phenology, NSC storage and intra-annual growth were clearly different between species, highlighting their contrasting carbon allocation. Beech growth began just after budburst, with a maximal growth rate when the leaves were mature and variations in the NSC content were low. Thus, beech radial growth seemed highly dependent on leaf photosynthesis. For oak, earlywood quickly developed before budburst, which probably led to the starch decrease quantified in the stem from April to June. For pine, growth began before the needles unfolding and the lack of NSC decrease during the growing season suggested that the substrates for radial growth were new assimilates of the needles from the previous year. Only for oak, the pattern determined from the intra-annual growth measured using microcoring differed from the pattern determined from dendrometer data. For all species, the ring width was significantly influenced by growth duration and not by growth rate, which differs from previous studies. The observed between-species difference at the intra-annual scale is key information for anticipating suitability of future species in temperate forests.
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differing growth responses to climatic variations and soil water deficits of fagus sylvatica Quercus Petraea and pinus sylvestris in a temperate forest
Forest Ecology and Management, 2012Co-Authors: Nathalie Bréda, Eric Dufrêne, Alice Michelot, Claire DamesinAbstract:Abstract In addition to global warming, the frequency and the intensity of droughts will probably increase in central and southern Europe. Resulting climate changes and soil water deficits could alter tree growth, according to sensitivity of each species. The aim of this study was to compare the growth response of three European species (Fagus sylvatica, Quercus Petraea and Pinus sylvestris) to climatic variations and soil water deficits in the same temperate forest. Three mature stands per species were sampled to obtain earlywood, latewood and total ring chronologies from 1960 to 2007. Climate–growth relationships were established by bootstrapped correlations and response function analysis. Monthly bioclimatic regressors were simulated by a physiological water balance model that used daily climatic data and stand parameters to estimate soil water deficits. Our results highlighted a common sensitivity to precipitation from May to July for the dominant tree growth of the three species but also differences in the species vulnerability to climate and soil water deficits. Beech was the most sensitive species to the climatic conditions of the current growing season. Beech growth was positively correlated with precipitation from May to July and negatively with maximal temperatures in June and July. Oak growth was negatively correlated with minimal temperatures in the previous August and September and positively with precipitation in the previous October and December during pointer years. This led to long-term consequences for growth, probably due to carbon reserve depletion. Pine growth was positively influenced by warm December but was also vulnerable to maximal temperatures and soil water deficits from June to August. The climate in August only influenced the pine growth probably because the growing season of pine was longer than that of the deciduous species. For both oak and pine, latewood was the component that was most sensitive to climatic variations and soil water deficits. According to the study findings, an increase in the frequency and the intensity of droughts could affect the three species. Maximum summer temperatures could have negative impacts for beech and pine growth. Dry and warm autumns could lead to long-term consequences and decrease the oak growth.
Antoine Kremer - One of the best experts on this subject based on the ideXlab platform.
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Characterisation and natural variation of a dehydrin gene in Quercus Petraea (Matt.) Liebl.
Plant Biology, 2011Co-Authors: B. Vornam, Antoine Kremer, O. Gailing, Jérémy Derory, Christophe Plomion, Reiner FinkeldeyAbstract:For the first time in sessile oak [Quercus Petraea (Matt.) Liebl.], the isolation and characterisation of a full-length dehydrin gene and its promoter region, as well as its allelic variation in natural populations, is reported. Dehydrins (Dhn) are stress-related genes important for the survival of perennial plants in a seasonal climate. A full-length dehydrin gene (Dhn3) was characterised at the nucleotide level and the protein structure was modelled. Additionally, the allelic variation was analysed in five natural populations of Quercus Petraea (Matt.) Liebl. sampled along an altitudinal gradient in the French Pyrenees. The analysed sequences contain typical domains of the K(n) class of dehydrins in the coding region. Also, the 5'untranslated region (promoter) of the gene was amplified, which shows typical motifs essential for drought- and cold-responsive gene expression. Single nucleotide substitutions and indels (insertions/deletions) within the coding region determine large biochemical differences at the protein level. However, only low levels of genetic differentiation between populations from different altitudes were detectable.
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Leaf morphological differentiation between Quercus robur and Quercus Petraea is stable across western European mixed oak stands
Annals of Forest Sciences, 2002Co-Authors: Antoine Kremer, Jochen Kleinschmit, Santiago Espinel, Jan Jensen, Ulrike Csaikl, Reiner Finkeldey, Joan Cottrell, Jean-luc Dupouey, J. D. Deans, Barbara Van DamAbstract:Leaf morphology was assessed in nine mixed oak stands (Quercus Petraea and Q. robur) located in eight European countries. Exhaustive sampling was used in an area of each stand where the two species coexisted in approximately equal proportions (about 170 trees/spe-cies/stand). Fourteen leaf characters were assessed on each of 5 to10 leaves collected from the upper part of each tree. Three multivariate statisti-cal techniques (CDA, canonical discriminant analysis; PCA, principal component analysis; MCA, multiple correspondence analysis) were used in two different ways: first on the total set of leaves over all stands (global analysis) and second, separately within each stand (local analysis). There was a general agreement of the results among the statistical methods used and between the analyses conducted (global and local). The first synthetic variable derived by each multivariate analysis exhibited a clear and sharp bimodal distribution, with overlapping in the central part. The two modes were interpreted as the two species, and the overlapping region was interpreted as an area where the within-species variations were superimposed. There was no discontinuity in the distribution or no visible evidence of a third mode which would have indicated the exis-tence of a third population composed of trees with intermediate morphologies. Based on petiole length and number of intercalary veins, an “easy to use” discriminant function applicable to a major part of the natural distribution of the species was constructed. Validation on an independent set of trees provided a 98% rate of correct identification. The results were interpreted in the light of earlier reports about extensive hybridization occurring in mixed oak stands. Maternal effects on morphological characters, as well as a lower frequency or fitness of hybrids in comparison with parent species could explain the maintenance of two modes, which might be composed of either pure species or pure species and introgres-sed forms.
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within population genetic structure in Quercus robur l and Quercus Petraea matt liebl assessed with isozymes and microsatellites
Molecular Ecology, 1998Co-Authors: Rejane Streiff, Herta Steinkellner, Thierry Labbe, Roberto Bacilieri, Joseph Glossl, Antoine KremerAbstract:The spatial distribution of alleles is described in a forest stand of natural origin of 5 ha comprising 355 mature Quercus Petraea and Q. robur trees. Each tree was genotyped for six microsatellite loci. Previous studies on the same population based on isozymes allowed a comparison of different markers for the detection of spatial genetic structure. Different statistics were used: differentiation measures at different spatial scales, and spatial autocorrelation analysis based on Moran’s index I. For microsatellites, differentiation and autocorrelation were calculated with unordered alleles (identity in state) and with alleles ordered according to their size. Results showed the same tendency of a significant, but low, spatial genetic structure for markers and different statistics. Some differences could, however, be detected. First, microsatellites interpreted as unordered alleles exhibit stronger spatial structure than isozymes or microsatellite interpreted as ordered alleles. Second, differentiation and autocorrelation values were higher in Q. Petraea than in Q. robur. These differences were attributed to species differences in gene flow via pollen or seed.
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identification and characterization of ga ct n microsatellite loci from Quercus Petraea
Plant Molecular Biology, 1997Co-Authors: Herta Steinkellner, Antoine Kremer, S Fluch, E Turetschek, Christian Lexer, Rejane Streiff, Kornel Burg, Josef GlosslAbstract:In this study a size selected genomic library from Quercus Petraea was screened for (GA/CT)n-microsatellite sequences. The resulting loci were analysed by PCR for their usefulness as molecular markers in Q. Petraea and Q. robur. 17 out of 52 tested primer pairs resulted in the amplification of a polymorphic single-locus pattern. The number of alleles found per locus varied from 6 to 16. Combining the genetic variation observed for the characterized loci provides a unique genotype for all the individuals tested. Using intraspecific controlled crosses of Q. robur trees Mendelian inheritance could be shown for five loci.
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detection of genomic regions differentiating two closely related oak species Quercus Petraea matt liebl and Quercus robur l
Heredity, 1997Co-Authors: Catherine Bodénès, S Joandet, F Laigret, Antoine KremerAbstract:Genomic regions differentiating Quercus Petraea and Quercus robur were detected by screening 2800 PCR amplification products using random primers on 22 trees of each species sampled in 11 natural populations. Only two per cent of the amplified fragments exhibited significant frequency differences between the two species and none of them was specific to a species. The nucleotide divergence between the two species estimated with RAPD data was 0.5 per cent in the overall genome and increased to 3.3 per cent in the discriminant regions. Twenty-three informative fragments were cloned and partially sequenced. New primers were derived from these sequences to obtain Sequence Characterized Amplified Region (SCAR) fragments. Southern blot experiments indicated that the SCARs were generally in low copy number in the genome. A search for similarity between SCAR sequences and sequences contained in data banks revealed that three of them corresponded to known DNA sequences.
