Daniel Epron | Université de Lorraine (original) (raw)
Papers by Daniel Epron
The New phytologist, Jan 11, 2016
(13) CO2 pulse-labelling experiments were performed in situ on adult beeches (Fagus sylvatica) an... more (13) CO2 pulse-labelling experiments were performed in situ on adult beeches (Fagus sylvatica) and pines (Pinus pinaster) at different phenological stages to study seasonal and interspecific short-term dynamics and partitioning of recently assimilated carbon (C) in leaves. Polar fraction (PF, including soluble sugars, amino acids and organic acids) and starch were purified from foliage sampled during a 10-d chase period. C contents, isotopic compositions and (13) C dynamics parameters were determined in bulk foliage, PF and starch. Decrease in (13) C amount in bulk foliage followed a two-pool exponential model highlighting (13) C partitioning between 'mobile' and 'stable' pools, the relative proportion of the latter being maximal in beech leaves in May. Early in the growing season, new foliage acted as a strong C sink in both species, but although young leaves and needles were already photosynthesizing, the latter were still supplied with previous-year needle photosynthates 2 months after budburst. Mean (13) C residence times (MRT) were minimal in summer, indicating fast photosynthate export to supply perennial organ growth in both species. In late summer, MRT differed between senescing beech leaves and overwintering pine needles. Seasonal variations of (13) C partitioning and dynamics in field-grown tree foliage are closely linked to phenological differences between deciduous and evergreen trees.
Tree Physiology, 2012
Understanding the underlying mechanisms that account for the impact of potassium (K) fertilizatio... more Understanding the underlying mechanisms that account for the impact of potassium (K) fertilization and its replacement by sodium (Na) on tree growth is key to improving the management of forest plantations that are expanding over weathered tropical soils with low amounts of exchangeable bases. A complete randomized block design was planted with Eucalyptus grandis (W. Hill ex Maiden) to quantify growth, carbon uptake and carbon partitioning using a carbon budget approach. A combination of approaches including the establishment of allometric relationships over the whole rotation and measurements of soil CO 2 efflux and aboveground litterfall at the end of the rotation were used to estimate aboveground net production (ANPP), total belowground carbon flux and gross primary production (GPP). The stable carbon isotope (δ 13 C) of stem wood α-cellulose produced every year was used as a proxy for stomatal limitation of photosynthesis. Potassium fertilization increased GPP and decreased the fraction of carbon allocated belowground. Aboveground net production was strongly enhanced, and because leaf lifespan increased, leaf biomass was enhanced without any change in leaf production, and wood production (P W ) was dramatically increased. Sodium application decreased the fraction of carbon allocated belowground in a similar way, and enhanced GPP, ANPP and P W , but to a lesser extent compared with K fertilization. Neither K nor Na affected δ 13 C of stem wood α-cellulose, suggesting that water-use efficiency was the same among the treatments and that the inferred increase in leaf photosynthesis was not only related to a higher stomatal conductance. We concluded that the response to K fertilization and Na addition on P W resulted from drastic changes in carbon allocation.
Global Change Biology, 2006
Soil CO 2 efflux was measured in clear-cut and intact plots in order to quantify the impact of ha... more Soil CO 2 efflux was measured in clear-cut and intact plots in order to quantify the impact of harvest on soil respiration in an intensively managed Eucalyptus plantation, and to evaluate the increase in heterotrophic component of soil respiration because of the decomposition of harvest residues. Soil CO 2 effluxes showed a pronounced seasonal trend, which was well related to the pattern of precipitation and soil water content and were always significantly lower in the clear-cut plots than in the intact plots. On an annual basis, soil respiration represented 1.57 and 0.91 kg C m À2 yr À1 in intact and clearcut plots, respectively. During the first year following harvest, residues have lost 0.79 kg C m À2 yr À1 . Our estimate of heterotrophic respiration was calculated assuming that it was similar to soil respiration in the clear-cut area except that the decomposition of residues did not occur, and it was further corrected for differences in soil water content between intact and clear-cut plots and for the cessation of leaf and fine root turnover in clear cut. Heterotrophic respiration in clear-cut plots was estimated at 1.18 kg C m À2 yr À1 whereas it was only 0.65 kg C m À2 yr À1 in intact plots (41% of soil respiration). Assumptions and uncertainties with these calculations are discussed.
Tree physiology, Jan 9, 2015
Latex, the cytoplasm of laticiferous cells localized in the inner bark of rubber trees (Hevea bra... more Latex, the cytoplasm of laticiferous cells localized in the inner bark of rubber trees (Hevea brasiliensis Müll. Arg.), is collected by tapping the bark. Following tapping, latex flows out of the trunk and is regenerated, whereas in untapped trees, there is no natural exudation. It is still unknown whether the carbohydrates used for latex regeneration in tapped trees is coming from recent photosynthates or from stored carbohydrates, and in the former case, it is expected that latex carbon isotope composition of tapped trees will vary seasonally, whereas latex isotope composition of untapped trees will be more stable. Temporal variations of carbon isotope composition of trunk latex (δ(13)C-L), leaf soluble compounds (δ(13)C-S) and bulk leaf material (δ(13)C-B) collected from tapped and untapped 20-year-old trees were compared. A marked difference in δ(13)C-L was observed between tapped and untapped trees whatever the season. Trunk latex from tapped trees was more depleted (1.6‰ on av...
Carbon allocation belowground competes with aboveground growth and biomass production. In the oth... more Carbon allocation belowground competes with aboveground growth and biomass production. In the other hand, it contributes to resource acquisition such as nutrient, water and carbon sequestration in soil. Thus, a better characterization of carbon flow from plant to soil and its residence time within each compartment is an important issue for understanding and modeling forest ecosystem carbon budget. 13C pulse
Soil Biology and Biochemistry, 2015
Journal of Applied Biosciences, 2014
Forest Ecology and Management, 2013
The association of N 2 -fixing species (NFS) could be an attractive option for achieving a sustai... more The association of N 2 -fixing species (NFS) could be an attractive option for achieving a sustainable increase of Eucalyptus plantations (EP) productivity through a positive balance between facilitative effects and competition between species. A randomised block design was replicated at four sites (Cenibra, USP, Suzano and IP) in Southern Brazil and at one site in Congo. The development of mono-specific stands of Acacia mangium (100A) and Eucalyptus grandis or urophylla  grandis (100E), was compared with N fertilisation treatment (100E + N) and with mixed-species plantations in a 1:1 ratio (50A:50E), and in an additive series with varying densities of acacia for the same density of eucalypt (25A:100E, 50A:100E, 100A:100E). The objectives were to assess the effect of mixtures on tree growth and stand production, and the behaviour of the two species in contrasting soil and climatic conditions. Tree growth was monitored over stand rotation and the biomass of aboveground tree components estimated at mid-rotation and at harvesting age. Eucalyptus height was 13% higher in Brazil than in Congo. Favourable ecological conditions in Congo and Cenibra led to 50% higher Acacia tree height than at the other sites. A depressive effect of Eucalyptus neighbour trees on Acacia height and circumference growth, lower in Congo than in Brazil, was observed in the mixtures from age 1-2 years onwards. Depressive effects of acacia on eucalypt height and circumference growth were low in USP, Suzano and IP, high in Cenibra, and not observed in Congo, in 50A:50E and 25A:100E. A positive though insignificant response to N fertilisation was only found in USP and Congo. Complementarity for light and soil resource capture between Eucalyptus and Acacia trees resulted in mean annual increments in total stand stemwood biomass (MAI) that were 7-15%, 6-12%, and 40% higher in the additive series than for 100E in Cenibra, USP and Congo, respectively at mid-rotation. Whilst lasting complementarity and facilitation in Congo led to 17-34% higher MAI in mixtures than for 100E at harvesting age, MAIs were not significantly higher in mixtures than for 100E in Brazil. Mixed-species plantations of Eucalyptus and A. mangium might enhance aboveground stand production on poor nutrient soils in warm and humid tropical climates with low water limitations.
Annales des Sciences Forestières, 1996
— Four-year-old potted saplings of Quercus petraea (Matt) Liebl were exposed to water short... more — Four-year-old potted saplings of Quercus petraea (Matt) Liebl were exposed to water shortage by withholding irrigation. After 10 days, predawn leaf water potential was decreased to -2.0 MPa and leaf photosynthesis was reduced by 55%. At this stage, starch and sucrose concentrations were decreased by 47 and 48%, respectively. A five-fold increase was observed in glucose and fructose concentrations of water-stressed saplings compared with well-watered plants. These results suggested that drought-induced changes in sugar composition contribute to osmotic adjustment in this species. oak / Quercus / soluble carbohydrate / starch / sucrose / water stress Résumé — Amidon et glucides solubles dans les feuilles de jeunes plants de chêne soumis à un deficit hydrique. Des jeunes plants en pot de Quercus petraea (Matt) Liebl âgés de 4 ans ont été soumis à un déficit hydrique en supprimant l'irrigation. Après 10 jours, le potentiel hydrique en fin de nuit était de -2,0 MPa et la photosynthèse foliaire réduite de 55 %. À ce stade, les concentrations en amidon et en saccharose étaient diminuées de 47 et 48 % respectivement. Les concentrations foliaires en glucose et en fructose des plants soumis à la sécheresse étaient augmentées d'un facteur 5 par rapport aux plants bien irrigués. Ces résultats suggèrent que les changements de la composition glucidique des feuilles lors d'un déficit hydrique contribuent à un ajustement osmotique chez cette espèce. chêne / Quercus / déficit hydrique / amidon / saccharose / glucide soluble * Present address: Institut des sciences et des techniques de l'environnement, pôle universitaire du Pays de Montbéliard, BP 427, 25211 Montbéliard cedex, France.
ANNALS OF FOREST SCIENCE, 1999
Root and shoot biomass of oak seedlings were reduced after 9 days of watering with a nutrient sol... more Root and shoot biomass of oak seedlings were reduced after 9 days of watering with a nutrient solution containing either 50 or 250 mM NaCl. Both moderate and high salinity treatment strongly altered root elongation. In contrast, specific respiration of roots was unaffected by the moderate salinity treatment while it was reduced by 62 % after 9 days of watering with a nutrient solution containing 250 mM NaCl. Na + content strongly increased in all plant tissues with increasing NaCl concentration in the nutrient solution. Na + contents in leaves and in twigs were lower than in roots at 50 mM NaCl in the nutrient solution while they were similar at 250 mM. Prevention of Na + translocation in shoot in moderately stressed oak probably requires extra energy, which may be provided by an increase in maintenance respiration. At higher salinity (250 mM), root respiration was strongly inhibited, which might explain the inability of severely stressed oak seedling to prevent Na + translocation to the shoot. An increase in the respiratory cost for maintenance, for active ion transport and/or for growth processes in oak root encountering sodium chloride salinity is therefore consistent with the occurrence of a high rate of root respiration while growth rate was reduced. (© Inra/Elsevier, Paris.)
Tree physiology, 2009
The study of the fate of assimilated carbon in respiratory fluxes in the field is needed to resol... more The study of the fate of assimilated carbon in respiratory fluxes in the field is needed to resolve the residence and transfer times of carbon in the atmosphere-plant-soil system in forest ecosystems, but it requires high frequency measurements of the isotopic composition of evolved CO2. We developed a closed transparent chamber to label the whole crown of a tree and a labelling system capable of delivering a 3-h pulse of 99% 13CO2 in the field. The isotopic compositions of trunk and soil CO2 effluxes were recorded continuously on two labelled and one control trees by a tuneable diode laser absorption spectrometer during a 2-month chase period following the late summer labelling. The lag times for trunk CO2 effluxes are consistent with a phloem sap velocity of about 1 m h(-1). The isotopic composition (delta13C) of CO2 efflux from the trunk was maximal 2-3 days after labelling and declined thereafter following two exponential decays with a half-life of 2-8 days for the first and a h...
Journal of Tropical Ecology, 2006
∗ Université Henri Poincaré-Nancy 1, UMR 1137 INRA UHP Ecologie et Ecophysiologie foresti`eres, F... more ∗ Université Henri Poincaré-Nancy 1, UMR 1137 INRA UHP Ecologie et Ecophysiologie foresti`eres, Faculté des Sciences, BP 239, 54506 Vandoeuvre, France INRA, UR Bioclimatologie 'Ecologie Fonctionnelle et Physique de l'Environnement' 69 rte d'Arcachon, 33612 Cestas ...
Plant and Soil, 2009
Abstract The high spatial variability of soil respiration in tropical rainforests is well evaluat... more Abstract The high spatial variability of soil respiration in tropical rainforests is well evaluated, but influences of biotic factors are not clearly understood. This study underlines the influence of tree species characteristics on soil respiration across a 16-monospecific plot design in ...
![Research paper thumbnail of Soil CO2 efflux in a beech forest: the contribution of root respiration [carbon cycle]](https://attachments.academia-assets.com/45949664/thumbnails/1.jpg)
](The contribution of root respiration to soil carbon efflux in a young beech stand was estimated b... more The contribution of root respiration to soil carbon efflux in a young beech stand was estimated by comparing soil CO, efflux from small trenched plots to efflux from undisturbed areas (main plot). Soil CO 2 efflux was measured every 2-4 weeks in 1997. An empirical model (y = A q v e BT ) was fitted to the soil CO, efflux data and was used to calculate annual soil carbon efflux from soil temperature (T) and soil volumetric water content (q v ). The annual soil carbon efflux were 0.66 kg C m -2 year -1 in the main plot and 0.42 kg C m -2 year -1 in the trenched plots. The difference between these two estimations was corrected for the decomposition of roots that were killed following trenching. The heterotrophic component of soil carbon efflux accounts for 40 % of total soil carbon efflux (0.26 kg C m -2 year -1 ) while root respiration accounts for 60 % of soil C release (0.40 kg C m -2 year -1 ). (© Inra/Elsevier, Paris.) carbon cycle / Fagus sylvatica L. / respiration / root / soil CO 2 efflux Résumé -Flux de CO 2 provenant du sol dans une hêtraie : la contribution de la respiration des racines. La contribution de la respiration des racines au tlux de carbone provenant du sol d'une jeune hêtraie a été estimée en comparant le flux de CO, provenant du sol sur des petites placettes isolées par une tranchée au flux de CO, provenant du sol mesuré sur la placette principale. Le flux de CO, provenant du sol a été mesuré toutes les 2 à 4 semaines en 1997. Un modèle empirique (y = A & t h e t a s ; v e BT ) a été ajusté sur les données de flux de CO 2 provenant du sol, et utilisé pour calculer le flux annuel de carbone provenant du sol à partir de la température du sol (T) et de la teneur en eau volumique du sol (&thetas; v ). Les flux annuels de carbone provenant du sol étaient de 0,66 kg C m -2 y -1 pour la placette principale et de 0,42 kg C m -2 y -1 pour les petites placettes isolées par une tranchée. La différence entre les deux estimations a été corrigée pour prendre en compte la décomposition des racines tuées lors de l'établissement de la tranchée. La composante hétérotrophe représente 40 % du flux total de carbone provenant du sol (0,26 kg C m -2 y -1 ) alors que la respiration des racines représente 60 % du dégagement de carbone (0,40 kg C m -2 y -1 ). (© Inra/Elsevier, Paris.) cycle du carbone / Fagus sylvatica L. / respiration / racine / flux de CO, provenant du sol.
The New phytologist, Jan 11, 2016
(13) CO2 pulse-labelling experiments were performed in situ on adult beeches (Fagus sylvatica) an... more (13) CO2 pulse-labelling experiments were performed in situ on adult beeches (Fagus sylvatica) and pines (Pinus pinaster) at different phenological stages to study seasonal and interspecific short-term dynamics and partitioning of recently assimilated carbon (C) in leaves. Polar fraction (PF, including soluble sugars, amino acids and organic acids) and starch were purified from foliage sampled during a 10-d chase period. C contents, isotopic compositions and (13) C dynamics parameters were determined in bulk foliage, PF and starch. Decrease in (13) C amount in bulk foliage followed a two-pool exponential model highlighting (13) C partitioning between 'mobile' and 'stable' pools, the relative proportion of the latter being maximal in beech leaves in May. Early in the growing season, new foliage acted as a strong C sink in both species, but although young leaves and needles were already photosynthesizing, the latter were still supplied with previous-year needle photosynthates 2 months after budburst. Mean (13) C residence times (MRT) were minimal in summer, indicating fast photosynthate export to supply perennial organ growth in both species. In late summer, MRT differed between senescing beech leaves and overwintering pine needles. Seasonal variations of (13) C partitioning and dynamics in field-grown tree foliage are closely linked to phenological differences between deciduous and evergreen trees.
Tree Physiology, 2012
Understanding the underlying mechanisms that account for the impact of potassium (K) fertilizatio... more Understanding the underlying mechanisms that account for the impact of potassium (K) fertilization and its replacement by sodium (Na) on tree growth is key to improving the management of forest plantations that are expanding over weathered tropical soils with low amounts of exchangeable bases. A complete randomized block design was planted with Eucalyptus grandis (W. Hill ex Maiden) to quantify growth, carbon uptake and carbon partitioning using a carbon budget approach. A combination of approaches including the establishment of allometric relationships over the whole rotation and measurements of soil CO 2 efflux and aboveground litterfall at the end of the rotation were used to estimate aboveground net production (ANPP), total belowground carbon flux and gross primary production (GPP). The stable carbon isotope (δ 13 C) of stem wood α-cellulose produced every year was used as a proxy for stomatal limitation of photosynthesis. Potassium fertilization increased GPP and decreased the fraction of carbon allocated belowground. Aboveground net production was strongly enhanced, and because leaf lifespan increased, leaf biomass was enhanced without any change in leaf production, and wood production (P W ) was dramatically increased. Sodium application decreased the fraction of carbon allocated belowground in a similar way, and enhanced GPP, ANPP and P W , but to a lesser extent compared with K fertilization. Neither K nor Na affected δ 13 C of stem wood α-cellulose, suggesting that water-use efficiency was the same among the treatments and that the inferred increase in leaf photosynthesis was not only related to a higher stomatal conductance. We concluded that the response to K fertilization and Na addition on P W resulted from drastic changes in carbon allocation.
Global Change Biology, 2006
Soil CO 2 efflux was measured in clear-cut and intact plots in order to quantify the impact of ha... more Soil CO 2 efflux was measured in clear-cut and intact plots in order to quantify the impact of harvest on soil respiration in an intensively managed Eucalyptus plantation, and to evaluate the increase in heterotrophic component of soil respiration because of the decomposition of harvest residues. Soil CO 2 effluxes showed a pronounced seasonal trend, which was well related to the pattern of precipitation and soil water content and were always significantly lower in the clear-cut plots than in the intact plots. On an annual basis, soil respiration represented 1.57 and 0.91 kg C m À2 yr À1 in intact and clearcut plots, respectively. During the first year following harvest, residues have lost 0.79 kg C m À2 yr À1 . Our estimate of heterotrophic respiration was calculated assuming that it was similar to soil respiration in the clear-cut area except that the decomposition of residues did not occur, and it was further corrected for differences in soil water content between intact and clear-cut plots and for the cessation of leaf and fine root turnover in clear cut. Heterotrophic respiration in clear-cut plots was estimated at 1.18 kg C m À2 yr À1 whereas it was only 0.65 kg C m À2 yr À1 in intact plots (41% of soil respiration). Assumptions and uncertainties with these calculations are discussed.
Tree physiology, Jan 9, 2015
Latex, the cytoplasm of laticiferous cells localized in the inner bark of rubber trees (Hevea bra... more Latex, the cytoplasm of laticiferous cells localized in the inner bark of rubber trees (Hevea brasiliensis Müll. Arg.), is collected by tapping the bark. Following tapping, latex flows out of the trunk and is regenerated, whereas in untapped trees, there is no natural exudation. It is still unknown whether the carbohydrates used for latex regeneration in tapped trees is coming from recent photosynthates or from stored carbohydrates, and in the former case, it is expected that latex carbon isotope composition of tapped trees will vary seasonally, whereas latex isotope composition of untapped trees will be more stable. Temporal variations of carbon isotope composition of trunk latex (δ(13)C-L), leaf soluble compounds (δ(13)C-S) and bulk leaf material (δ(13)C-B) collected from tapped and untapped 20-year-old trees were compared. A marked difference in δ(13)C-L was observed between tapped and untapped trees whatever the season. Trunk latex from tapped trees was more depleted (1.6‰ on av...
Carbon allocation belowground competes with aboveground growth and biomass production. In the oth... more Carbon allocation belowground competes with aboveground growth and biomass production. In the other hand, it contributes to resource acquisition such as nutrient, water and carbon sequestration in soil. Thus, a better characterization of carbon flow from plant to soil and its residence time within each compartment is an important issue for understanding and modeling forest ecosystem carbon budget. 13C pulse
Soil Biology and Biochemistry, 2015
Journal of Applied Biosciences, 2014
Forest Ecology and Management, 2013
The association of N 2 -fixing species (NFS) could be an attractive option for achieving a sustai... more The association of N 2 -fixing species (NFS) could be an attractive option for achieving a sustainable increase of Eucalyptus plantations (EP) productivity through a positive balance between facilitative effects and competition between species. A randomised block design was replicated at four sites (Cenibra, USP, Suzano and IP) in Southern Brazil and at one site in Congo. The development of mono-specific stands of Acacia mangium (100A) and Eucalyptus grandis or urophylla  grandis (100E), was compared with N fertilisation treatment (100E + N) and with mixed-species plantations in a 1:1 ratio (50A:50E), and in an additive series with varying densities of acacia for the same density of eucalypt (25A:100E, 50A:100E, 100A:100E). The objectives were to assess the effect of mixtures on tree growth and stand production, and the behaviour of the two species in contrasting soil and climatic conditions. Tree growth was monitored over stand rotation and the biomass of aboveground tree components estimated at mid-rotation and at harvesting age. Eucalyptus height was 13% higher in Brazil than in Congo. Favourable ecological conditions in Congo and Cenibra led to 50% higher Acacia tree height than at the other sites. A depressive effect of Eucalyptus neighbour trees on Acacia height and circumference growth, lower in Congo than in Brazil, was observed in the mixtures from age 1-2 years onwards. Depressive effects of acacia on eucalypt height and circumference growth were low in USP, Suzano and IP, high in Cenibra, and not observed in Congo, in 50A:50E and 25A:100E. A positive though insignificant response to N fertilisation was only found in USP and Congo. Complementarity for light and soil resource capture between Eucalyptus and Acacia trees resulted in mean annual increments in total stand stemwood biomass (MAI) that were 7-15%, 6-12%, and 40% higher in the additive series than for 100E in Cenibra, USP and Congo, respectively at mid-rotation. Whilst lasting complementarity and facilitation in Congo led to 17-34% higher MAI in mixtures than for 100E at harvesting age, MAIs were not significantly higher in mixtures than for 100E in Brazil. Mixed-species plantations of Eucalyptus and A. mangium might enhance aboveground stand production on poor nutrient soils in warm and humid tropical climates with low water limitations.
Annales des Sciences Forestières, 1996
— Four-year-old potted saplings of Quercus petraea (Matt) Liebl were exposed to water short... more — Four-year-old potted saplings of Quercus petraea (Matt) Liebl were exposed to water shortage by withholding irrigation. After 10 days, predawn leaf water potential was decreased to -2.0 MPa and leaf photosynthesis was reduced by 55%. At this stage, starch and sucrose concentrations were decreased by 47 and 48%, respectively. A five-fold increase was observed in glucose and fructose concentrations of water-stressed saplings compared with well-watered plants. These results suggested that drought-induced changes in sugar composition contribute to osmotic adjustment in this species. oak / Quercus / soluble carbohydrate / starch / sucrose / water stress Résumé — Amidon et glucides solubles dans les feuilles de jeunes plants de chêne soumis à un deficit hydrique. Des jeunes plants en pot de Quercus petraea (Matt) Liebl âgés de 4 ans ont été soumis à un déficit hydrique en supprimant l'irrigation. Après 10 jours, le potentiel hydrique en fin de nuit était de -2,0 MPa et la photosynthèse foliaire réduite de 55 %. À ce stade, les concentrations en amidon et en saccharose étaient diminuées de 47 et 48 % respectivement. Les concentrations foliaires en glucose et en fructose des plants soumis à la sécheresse étaient augmentées d'un facteur 5 par rapport aux plants bien irrigués. Ces résultats suggèrent que les changements de la composition glucidique des feuilles lors d'un déficit hydrique contribuent à un ajustement osmotique chez cette espèce. chêne / Quercus / déficit hydrique / amidon / saccharose / glucide soluble * Present address: Institut des sciences et des techniques de l'environnement, pôle universitaire du Pays de Montbéliard, BP 427, 25211 Montbéliard cedex, France.
ANNALS OF FOREST SCIENCE, 1999
Root and shoot biomass of oak seedlings were reduced after 9 days of watering with a nutrient sol... more Root and shoot biomass of oak seedlings were reduced after 9 days of watering with a nutrient solution containing either 50 or 250 mM NaCl. Both moderate and high salinity treatment strongly altered root elongation. In contrast, specific respiration of roots was unaffected by the moderate salinity treatment while it was reduced by 62 % after 9 days of watering with a nutrient solution containing 250 mM NaCl. Na + content strongly increased in all plant tissues with increasing NaCl concentration in the nutrient solution. Na + contents in leaves and in twigs were lower than in roots at 50 mM NaCl in the nutrient solution while they were similar at 250 mM. Prevention of Na + translocation in shoot in moderately stressed oak probably requires extra energy, which may be provided by an increase in maintenance respiration. At higher salinity (250 mM), root respiration was strongly inhibited, which might explain the inability of severely stressed oak seedling to prevent Na + translocation to the shoot. An increase in the respiratory cost for maintenance, for active ion transport and/or for growth processes in oak root encountering sodium chloride salinity is therefore consistent with the occurrence of a high rate of root respiration while growth rate was reduced. (© Inra/Elsevier, Paris.)
Tree physiology, 2009
The study of the fate of assimilated carbon in respiratory fluxes in the field is needed to resol... more The study of the fate of assimilated carbon in respiratory fluxes in the field is needed to resolve the residence and transfer times of carbon in the atmosphere-plant-soil system in forest ecosystems, but it requires high frequency measurements of the isotopic composition of evolved CO2. We developed a closed transparent chamber to label the whole crown of a tree and a labelling system capable of delivering a 3-h pulse of 99% 13CO2 in the field. The isotopic compositions of trunk and soil CO2 effluxes were recorded continuously on two labelled and one control trees by a tuneable diode laser absorption spectrometer during a 2-month chase period following the late summer labelling. The lag times for trunk CO2 effluxes are consistent with a phloem sap velocity of about 1 m h(-1). The isotopic composition (delta13C) of CO2 efflux from the trunk was maximal 2-3 days after labelling and declined thereafter following two exponential decays with a half-life of 2-8 days for the first and a h...
Journal of Tropical Ecology, 2006
∗ Université Henri Poincaré-Nancy 1, UMR 1137 INRA UHP Ecologie et Ecophysiologie foresti`eres, F... more ∗ Université Henri Poincaré-Nancy 1, UMR 1137 INRA UHP Ecologie et Ecophysiologie foresti`eres, Faculté des Sciences, BP 239, 54506 Vandoeuvre, France INRA, UR Bioclimatologie 'Ecologie Fonctionnelle et Physique de l'Environnement' 69 rte d'Arcachon, 33612 Cestas ...
Plant and Soil, 2009
Abstract The high spatial variability of soil respiration in tropical rainforests is well evaluat... more Abstract The high spatial variability of soil respiration in tropical rainforests is well evaluated, but influences of biotic factors are not clearly understood. This study underlines the influence of tree species characteristics on soil respiration across a 16-monospecific plot design in ...
The contribution of root respiration to soil carbon efflux in a young beech stand was estimated b... more The contribution of root respiration to soil carbon efflux in a young beech stand was estimated by comparing soil CO, efflux from small trenched plots to efflux from undisturbed areas (main plot). Soil CO 2 efflux was measured every 2-4 weeks in 1997. An empirical model (y = A q v e BT ) was fitted to the soil CO, efflux data and was used to calculate annual soil carbon efflux from soil temperature (T) and soil volumetric water content (q v ). The annual soil carbon efflux were 0.66 kg C m -2 year -1 in the main plot and 0.42 kg C m -2 year -1 in the trenched plots. The difference between these two estimations was corrected for the decomposition of roots that were killed following trenching. The heterotrophic component of soil carbon efflux accounts for 40 % of total soil carbon efflux (0.26 kg C m -2 year -1 ) while root respiration accounts for 60 % of soil C release (0.40 kg C m -2 year -1 ). (© Inra/Elsevier, Paris.) carbon cycle / Fagus sylvatica L. / respiration / root / soil CO 2 efflux Résumé -Flux de CO 2 provenant du sol dans une hêtraie : la contribution de la respiration des racines. La contribution de la respiration des racines au tlux de carbone provenant du sol d'une jeune hêtraie a été estimée en comparant le flux de CO, provenant du sol sur des petites placettes isolées par une tranchée au flux de CO, provenant du sol mesuré sur la placette principale. Le flux de CO, provenant du sol a été mesuré toutes les 2 à 4 semaines en 1997. Un modèle empirique (y = A & t h e t a s ; v e BT ) a été ajusté sur les données de flux de CO 2 provenant du sol, et utilisé pour calculer le flux annuel de carbone provenant du sol à partir de la température du sol (T) et de la teneur en eau volumique du sol (&thetas; v ). Les flux annuels de carbone provenant du sol étaient de 0,66 kg C m -2 y -1 pour la placette principale et de 0,42 kg C m -2 y -1 pour les petites placettes isolées par une tranchée. La différence entre les deux estimations a été corrigée pour prendre en compte la décomposition des racines tuées lors de l'établissement de la tranchée. La composante hétérotrophe représente 40 % du flux total de carbone provenant du sol (0,26 kg C m -2 y -1 ) alors que la respiration des racines représente 60 % du dégagement de carbone (0,40 kg C m -2 y -1 ). (© Inra/Elsevier, Paris.) cycle du carbone / Fagus sylvatica L. / respiration / racine / flux de CO, provenant du sol.