24 results on '"Medlyn BE"'
Search Results
2. High safety margins to drought‐induced hydraulic failure found in five pasture grasses
- Author
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Jacob, Vinod, primary, Choat, Brendan, additional, Churchill, Amber C., additional, Zhang, Haiyang, additional, Barton, Craig V. M., additional, Krishnananthaselvan, Arjunan, additional, Post, Alison K., additional, Power, Sally A., additional, Medlyn, Belinda E., additional, and Tissue, David T., additional
- Published
- 2022
- Full Text
- View/download PDF
3. Mechanisms of xylem hydraulic recovery after drought in Eucalyptus saligna
- Author
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Gauthey, Alice, primary, Peters, Jennifer M. R., additional, Lòpez, Rosana, additional, Carins‐Murphy, Madeline R., additional, Rodriguez‐Dominguez, Celia M., additional, Tissue, David T., additional, Medlyn, Belinda E., additional, Brodribb, Tim J., additional, and Choat, Brendan, additional
- Published
- 2022
- Full Text
- View/download PDF
4. No evidence for triose phosphate limitation of light‐saturated leaf photosynthesis under current atmospheric CO2concentration
- Author
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Mark G. Tjoelker, Dushan Kumarathunge, John E. Drake, Alistair Rogers, and Belinda E. Medlyn
- Subjects
0106 biological sciences ,0301 basic medicine ,biology ,Physiology ,ved/biology ,ved/biology.organism_classification_rank.species ,RuBisCO ,Biosphere ,Plant Science ,Phosphate ,Photosynthesis ,01 natural sciences ,Tundra ,C3 photosynthesis ,03 medical and health sciences ,chemistry.chemical_compound ,030104 developmental biology ,chemistry ,Co2 concentration ,Environmental chemistry ,Terrestrial plant ,biology.protein ,010606 plant biology & botany - Abstract
The triose phosphate utilization (TPU) rate has been identified as one of the processes that can limit terrestrial plant photosynthesis. However, we lack a robust quantitative assessment of TPU limitation of photosynthesis at the global scale. As a result, TPU, and its potential limitation of photosynthesis, is poorly represented in terrestrial biosphere models (TBMs). In this study, we utilized a global data set of photosynthetic CO2 response curves representing 141 species from tropical rainforests to Arctic tundra. We quantified TPU by fitting the standard biochemical model of C3 photosynthesis to measured photosynthetic CO2 response curves and characterized its instantaneous temperature response. Our results demonstrate that TPU does not limit leaf photosynthesis at the current ambient atmospheric CO2 concentration. Furthermore, our results showed that the light-saturated photosynthetic rates of plants growing in cold environments are not more often limited by TPU than those of plants growing in warmer environments. In addition, our study showed that the instantaneous temperature response of TPU is distinct from temperature response of the maximum rate of Rubisco carboxylation. The new formulations of the temperature response of TPU derived in this study may prove useful in quantifying the biochemical limits to terrestrial plant photosynthesis and improve the representation of plant photosynthesis in TBMs.
- Published
- 2019
5. Tree hydraulic traits are coordinated and strongly linked to climate-of-origin across a rainfall gradient
- Author
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Chris J. Blackman, Brendan Choat, Remko A. Duursma, Belinda E. Medlyn, Ximeng Li, David T. Tissue, and Paul D. Rymer
- Subjects
0106 biological sciences ,Ecophysiology ,Physiology ,Ecology ,Range (biology) ,Drought tolerance ,Xylem ,Plant Science ,Vegetation ,Biology ,010603 evolutionary biology ,01 natural sciences ,Arid ,Trait ,Adaptation ,010606 plant biology & botany - Abstract
Plant hydraulic traits capture the impacts of drought stress on plant function, yet vegetation models lack sufficient information regarding trait coordination and variation with climate-of-origin across species. Here, we investigated key hydraulic and carbon economy traits of 12 woody species in Australia from a broad climatic gradient, with the aim of identifying the coordination among these traits and the role of climate in shaping cross-species trait variation. The influence of environmental variation was minimized by a common garden approach, allowing us to factor out the influence of environment on phenotypic variation across species. We found that hydraulic traits (leaf turgor loss point, stomatal sensitivity to drought [Pgs ], xylem vulnerability to cavitation [Px ], and branch capacitance [Cbranch ]) were highly coordinated across species and strongly related to rainfall and aridity in the species native distributional range. In addition, trade-offs between drought tolerance and plant growth rate were observed across species. Collectively, these results provide critical insight into the coordination among hydraulic traits in modulating drought adaptation and will significantly advance our ability to predict drought vulnerability in these dominant trees species.
- Published
- 2018
6. Increased light-use efficiency sustains net primary productivity of shaded coffee plants in agroforestry system
- Author
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Elsa Defrenet, Guerric Le Maire, Peter Lehner, André Lacointe, Christophe Jourdan, Aurélie Cambou, Karel Van den Meersche, Anne Clément-Vidal, Remko A. Duursma, Philippe Vaast, Laurent Saint-André, Patricia Leandro, Belinda E. Medlyn, Clémentine Allinne, Fabien Charbonnier, Fernando Casanoves, Joannès Guillemot, Laura Jarri, Olivier Roupsard, Philippe Thaler, Alejandra Barquero Aguilar, Louise Audebert, Erwin Dreyer, and Emmanuelle Khac
- Subjects
2. Zero hunger ,010504 meteorology & atmospheric sciences ,biology ,Physiology ,Agroforestry ,business.industry ,Coffea arabica ,Coffea ,Microclimate ,Primary production ,04 agricultural and veterinary sciences ,Plant Science ,15. Life on land ,biology.organism_classification ,01 natural sciences ,Intraspecific competition ,Spatial heterogeneity ,Photosynthetically active radiation ,Agriculture ,040103 agronomy & agriculture ,0401 agriculture, forestry, and fisheries ,Environmental science ,business ,0105 earth and related environmental sciences - Abstract
In agroforestry systems, shade trees strongly affect the physiology of the undergrown crop. However, a major paradigm is that the reduction in absorbed photosynthetically active radiation is, to a certain extent, compensated by an increase in light-use efficiency, thereby reducing the difference in net primary productivity between shaded and non-shaded plants. Due to the large spatial heterogeneity in agroforestry systems and the lack of appropriate tools, the combined effects of such variables have seldom been analysed, even though they may help understand physiological processes underlying yield dynamics. In this study, we monitored net primary productivity, during two years, on scales ranging from individual coffee plants to the entire plot. Absorbed radiation was mapped with a 3D model (MAESPA). Light-use efficiency and net assimilation rate were derived for each coffee plant individually. We found that although irradiance was reduced by 60% below crowns of shade trees, coffee light-use efficiency increased by 50%, leaving net primary productivity fairly stable across all shade levels. Variability of aboveground net primary productivity of coffee plants was caused primarily by the age of the plants and by intraspecific competition among them (drivers usually overlooked in the agroforestry literature) rather than by the presence of shade trees.
- Published
- 2017
7. No evidence for triose phosphate limitation of light‐saturated leaf photosynthesis under current atmospheric CO2 concentration
- Author
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Kumarathunge, Dushan P., primary, Medlyn, Belinda E., additional, Drake, John E., additional, Rogers, Alistair, additional, and Tjoelker, Mark G., additional
- Published
- 2019
- Full Text
- View/download PDF
8. No evidence for triose phosphate limitation of light‐saturated leaf photosynthesis under current atmospheric CO2 concentration.
- Author
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Kumarathunge, Dushan P., Medlyn, Belinda E., Drake, John E., Rogers, Alistair, and Tjoelker, Mark G.
- Subjects
- *
PHOTOSYNTHESIS , *PHOTOSYNTHETIC rates , *RAIN forests , *BIOCHEMICAL models , *PHOSPHATES , *CARBOXYLATION - Abstract
The triose phosphate utilization (TPU) rate has been identified as one of the processes that can limit terrestrial plant photosynthesis. However, we lack a robust quantitative assessment of TPU limitation of photosynthesis at the global scale. As a result, TPU, and its potential limitation of photosynthesis, is poorly represented in terrestrial biosphere models (TBMs). In this study, we utilized a global data set of photosynthetic CO2 response curves representing 141 species from tropical rainforests to Arctic tundra. We quantified TPU by fitting the standard biochemical model of C3 photosynthesis to measured photosynthetic CO2 response curves and characterized its instantaneous temperature response. Our results demonstrate that TPU does not limit leaf photosynthesis at the current ambient atmospheric CO2 concentration. Furthermore, our results showed that the light‐saturated photosynthetic rates of plants growing in cold environments are not more often limited by TPU than those of plants growing in warmer environments. In addition, our study showed that the instantaneous temperature response of TPU is distinct from temperature response of the maximum rate of Rubisco carboxylation. The new formulations of the temperature response of TPU derived in this study may prove useful in quantifying the biochemical limits to terrestrial plant photosynthesis and improve the representation of plant photosynthesis in TBMs. We demonstrate that triose phosphate utilization rate does not limit leaf photosynthesis at the current ambient atmospheric CO2 concentration. Our results do not support the hypothesis that the light‐saturated photosynthetic rates of plants growing in cold environments are more often limited by triose phosphate utilization rate than those of plants growing in warmer environments. In addition, we showed that instantaneous temperature responses of triose phosphate utilization rate are distinct from temperature responses of the maximum rate of Rubisco carboxylation. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
9. Tree hydraulic traits are coordinated and strongly linked to climate‐of‐origin across a rainfall gradient
- Author
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Li, Ximeng, primary, Blackman, Chris J., additional, Choat, Brendan, additional, Duursma, Remko A., additional, Rymer, Paul D., additional, Medlyn, Belinda E., additional, and Tissue, David T., additional
- Published
- 2018
- Full Text
- View/download PDF
10. Optimal stomatal conductance in relation to photosynthesis in climatically contrastingEucalyptusspecies under drought
- Author
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Belinda E. Medlyn, Arnaud Heroult, Aimee E. Bourne, David S. Ellsworth, and Yan-Shih Lin
- Subjects
Stomatal conductance ,Agronomy ,Physiology ,Water cost ,Botany ,Water uptake ,Plant species ,Carbon gain ,Plant Science ,Biology ,Photosynthesis ,Eucalyptus ,Tree species - Abstract
Models of stomatal conductance (g(s)) are based on coupling between g(s) and CO(2) assimilation (A(net)), and it is often assumed that the slope of this relationship ('g(1) ') is constant across species. However, if different plant species have adapted to different access costs of water, then there will be differences in g(1) among species. We hypothesized that g(1) should vary among species adapted to different climates, and tested the theory and its linkage to plant hydraulics using four Eucalyptus species from different climatic origins in a common garden. Optimal stomatal theory predicts that species from sub-humid zones have a lower marginal water cost of C gain, hence lower g(1) than humid-zone species. In agreement with the theory that g(1) is related to tissue carbon costs for water supply, we found a relationship between wood density and g(1) across Eucalyptus species of contrasting climatic origins. There were significant reductions in the parameter g(1) during drought in humid but not sub-humid species, with the latter group maintaining g(1) in drought. There are strong differences in stomatal behaviour among related tree species in agreement with optimal stomatal theory, and these differences are consistent with the economics involved in water uptake and transport for carbon gain.
- Published
- 2012
11. Soil [N] modulates soil C cycling in CO2-fumigated tree stands: a meta-analysis
- Author
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K. S. Chigwerewe, P. De Angelis, Marion Liberloo, Michal V. Marek, Sebastiaan Luyssaert, Belinda E. Medlyn, Ivan A. Janssens, Radek Pokorný, V. Le Dantec, Craig V. M. Barton, Ana Maria Rey, G. Scarascia-Mugnozza, Seppo Kellomäki, Paul G. Jarvis, S. B. Broadmeadow, Otmar Urban, Reinhart Ceulemans, Eric Dufrêne, David T. Tingey, Wouter Dieleman, Vicky M. Temperton, Anne Kasurinen, M. S. J. Broadmeadow, and M. Crookshanks
- Subjects
0106 biological sciences ,2. Zero hunger ,010504 meteorology & atmospheric sciences ,Physiology ,Chemistry ,Fumigation ,chemistry.chemical_element ,Plant Science ,Soil carbon ,15. Life on land ,Carbon sequestration ,complex mixtures ,01 natural sciences ,Nitrogen ,Carbon cycle ,chemistry.chemical_compound ,Agronomy ,Soil water ,Carbon dioxide ,Cycling ,010606 plant biology & botany ,0105 earth and related environmental sciences - Abstract
Under elevated atmospheric CO2 concentrations, soil carbon (C) inputs are typically enhanced, suggesting larger soil C sequestration potential. However, soil C losses also increase and progressive nitrogen (N) limitation to plant growth may reduce the CO2 effect on soil C inputs with time. We compiled a data set from 131 manipulation experiments, and used meta-analysis to test the hypotheses that: (1) elevated atmospheric CO2 stimulates soil C inputs more than C losses, resulting in increasing soil C stocks; and (2) that these responses are modulated by N. Our results confirm that elevated CO2 induces a C allocation shift towards below-ground biomass compartments. However, the increased soil C inputs were offset by increased heterotrophic respiration (Rh), such that soil C content was not affected by elevated CO2. Soil N concentration strongly interacted with CO2 fumigation: the effect of elevated CO2 on fine root biomass and –production and on microbial activity increased with increasing soil N concentration, while the effect on soil C content decreased with increasing soil N concentration. These results suggest that both plant growth and microbial activity responses to elevated CO2 are modulated by N availability, and that it is essential to account for soil N concentration in C cycling analyses.
- Published
- 2010
12. Increased light-use efficiency sustains net primary productivity of shaded coffee plants in agroforestry system
- Author
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Charbonnier, Fabien, primary, Roupsard, Olivier, additional, le Maire, Guerric, additional, Guillemot, Joannès, additional, Casanoves, Fernando, additional, Lacointe, André, additional, Vaast, Philippe, additional, Allinne, Clémentine, additional, Audebert, Louise, additional, Cambou, Aurélie, additional, Clément-Vidal, Anne, additional, Defrenet, Elsa, additional, Duursma, Remko A., additional, Jarri, Laura, additional, Jourdan, Christophe, additional, Khac, Emmanuelle, additional, Leandro, Patricia, additional, Medlyn, Belinda E., additional, Saint-André, Laurent, additional, Thaler, Philippe, additional, Van Den Meersche, Karel, additional, Barquero Aguilar, Alejandra, additional, Lehner, Peter, additional, and Dreyer, Erwin, additional
- Published
- 2017
- Full Text
- View/download PDF
13. Temperature response of parameters of a biochemically based model of photosynthesis. II. A review of experimental data
- Author
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Kai-Yun Wang, Miko U. F. Kirschbaum, J. Strassemeyer, X. Le Roux, Denis Loustau, A. S. Walcroft, David S. Ellsworth, M. Forstreuter, Erwin Dreyer, Pierre Montpied, Belinda E. Medlyn, and Peter Harley
- Subjects
0106 biological sciences ,010504 meteorology & atmospheric sciences ,Physiology ,Chemistry ,Cold climate ,Cmax ,Analytical chemistry ,Plant Science ,15. Life on land ,Photosynthesis ,Crop species ,01 natural sciences ,Acclimatization ,RuBisCO activity ,13. Climate action ,Botany ,Temperature response ,010606 plant biology & botany ,0105 earth and related environmental sciences ,Maximum rate - Abstract
The temperature dependence of C 3 photosynthesis is known to vary with growth environment and with species. In an attempt to quantify this variability, a commonly used biochemically based photosynthesis model was parameterized from 19 gas exchange studies on tree and crop species. The parameter values obtained described the shape and amplitude of the temperature responses of the maximum rate of Rubisco activity ( V cmax ) and the potential rate of electron transport ( J max ). Original data sets were used for this review, as it is shown that derived values of V cmax and its temperature response depend strongly on assumptions made in derivation. Values of J max and V cmax at 25 ° C varied considerably among species but were strongly correlated, with an average J max : V cmax ratio of 1·67. Two species grown in cold climates, however, had lower ratios. In all studies, the J max : V cmax ratio declined strongly with measurement temperature. The relative temperature responses of J max and V cmax were relatively constant among tree species. Activation energies averaged 50 kJ mol − 1 for J max and 65 kJ mol − − − 1 for V cmax , and for most species temperature optima averaged 33 ° ° ° C for J max and 40 ° C for V cmax . However, the cold climate tree species had low temperature optima for both J max ( 19 ° C) and V cmax (29 ° ° ° C), suggesting acclimation of both processes to growth temperature. Crop species had somewhat different temperature responses, with higher activation energies for both J max and V cmax , implying narrower peaks in the temperature response for these species. The results thus suggest that both growth environment and
- Published
- 2002
14. Temperature response of parameters of a biochemically based model of photosynthesis. I. Seasonal changes in mature maritime pine (Pinus pinaster Ait.)
- Author
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Sylvain Delzon, Belinda E. Medlyn, and Denis Loustau
- Subjects
Stomatal conductance ,biology ,Physiology ,Vapour pressure of water ,Cmax ,chemistry.chemical_element ,Plant Science ,Seasonality ,biology.organism_classification ,Photosynthesis ,medicine.disease ,Nitrogen ,Acclimatization ,Animal science ,chemistry ,Botany ,medicine ,Pinus pinaster - Abstract
Responses of plant processes to temperature may vary according to the time scale on which they are measured. In this study, both short-term and seasonal responses of photosynthesis to temperature were examined. A field study of seasonal changes in the temperature response of photosynthesis was conducted on two provenances, French and Moroccan, of mature maritime pine ( Pinus pinaster Ait.). Measurements were made every 2 months over a 1-year period and used to parameterize a mechanistic model of photosynthesis. Temperature responses of maximum Rubisco activity, V cmax , and potential electron transport rate, J max , were obtained for each measurement period, as was the response of stomatal conductance, g s , to water vapour pressure deficit (VPD). Absolute values of V cmax and J max at 25 ° C were related to needle nitrogen content, N area. N area , and thus V cmax and J max , were negatively correlated with the mean minimum temperature in the month preceding measurements. The ratio of J max : V cmax at 25 ° C varied between 1 and 1·7 but did not show any seasonal trend. Nor was there any seasonal trend in the relative temperature response of V cmax , which had an activation energy H a of approximately 57 kJ mol − 1 throughout the experiment. The activation energy of J max was also close to constant throughout the experiment, averaging 39 kJ mol − 1 . For the French provenance, the optimal temperature of J max was positively correlated with the maximum temperature of the previous day, but no such correlation was found for the Moroccan provenance. The response of g s to VPD also varied seasonally, with much stronger stomatal closure in winter months. Taken together, these results implied a translational shift downwards of the photosynthetic temperature response curve with increasing T prev , and a shift in the temperature optimum of photosynthesis of 5‐10 ° C between summer and winter. These results illustrate that the short-term temperature response of photosynthesis varies significantly on a seasonal basis.
- Published
- 2002
15. Effects of elevated [CO2] on photosynthesis in European forest species: a meta-analysis of model parameters
- Author
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M. E. Jach, K. Laitinen, D. G.G. De Pury, Belinda E. Medlyn, E. Laitat, Seppo Kellomäki, Paul G. Jarvis, R. Liozon, Franz-W. Badeck, M. Forstreuter, Reinhart Ceulemans, M. S. J. Broadmeadow, Michal V. Marek, Ana Rey, Craig V. M. Barton, P. De Angelis, J. Strassemeyer, B. Portier, P. Roberntz, Kai-Yun Wang, and S. Philippot
- Subjects
Physiology ,AMAX ,chemistry.chemical_element ,Model parameters ,Plant Science ,Biology ,Atmospheric sciences ,Photosynthesis ,Electron transport chain ,Nitrogen ,chemistry.chemical_compound ,Model parameter ,chemistry ,RuBisCO activity ,Botany ,Carbon dioxide - Abstract
The effects of elevated atmospheric CO2 concentration on growth of forest tree species are difficult to predict because practical limitations restrict experiments to much shorter than the average life-span of a tree. Long-term, processbased computer models must be used to extrapolate from shorter-term experiments. A key problem is to ensure a strong flow of information between experiments and models. In this study, meta-analysis techniques were used to summarize a suite of photosynthetic model parameters obtained from 15 field-based elevated [CO2] experiments on European forest tree species. The parameters studied are commonly used in modelling photosynthesis, and include observed light-saturated photosynthetic rates (Amax), the potential electron transport rate (Jmax), the maximum Rubisco activity (Vcmax) and leaf nitrogen concentration on mass (Nm) and area (Na) bases. Across all experiments, light-saturated photosynthesis was strongly stimulated by growth in elevated [CO2]. However, significant down-regulation of photosynthesis was also observed; when measured at the same CO2 concentration, photosynthesis was reduced by 10‐20%. The underlying biochemistry of photosynthesis was affected, as shown by a down-regulation of the parameters Jmax and Vcmax of the order of 10%. This reduction in Jmax and Vcmax was linked to the effects of elevated [CO2] on leaf nitrogen concentration. It was concluded that the current model is adequate to model photosynthesis in elevated [CO2]. Tables of model parameter values for different European forest species are given.
- Published
- 1999
16. Optimal stomatal conductance in relation to photosynthesis in climatically contrasting Eucalyptus species under drought
- Author
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HÉROULT, ARNAUD, primary, LIN, YAN‐SHIH, additional, BOURNE, AIMEE, additional, MEDLYN, BELINDA E., additional, and ELLSWORTH, DAVID S., additional
- Published
- 2012
- Full Text
- View/download PDF
17. Soil [N] modulates soil C cycling in CO2‐fumigated tree stands: a meta‐analysis
- Author
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DIELEMAN, W. I. J., primary, LUYSSAERT, S., additional, REY, A., additional, DE ANGELIS, P., additional, BARTON, C. V. M., additional, BROADMEADOW, M. S. J., additional, BROADMEADOW, S. B., additional, CHIGWEREWE, K. S., additional, CROOKSHANKS, M., additional, DUFRÊNE, E., additional, JARVIS, P. G., additional, KASURINEN, A., additional, KELLOMÄKI, S., additional, LE DANTEC, V., additional, LIBERLOO, M., additional, MAREK, M., additional, MEDLYN, B., additional, POKORNÝ, R., additional, SCARASCIA‐MUGNOZZA, G., additional, TEMPERTON, V. M., additional, TINGEY, D., additional, URBAN, O., additional, CEULEMANS, R., additional, and JANSSENS, I. A., additional
- Published
- 2010
- Full Text
- View/download PDF
18. Temperature response of parameters of a biochemically based model of photosynthesis. I. Seasonal changes in mature maritime pine (Pinus pinaster Ait.)
- Author
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Medlyn, B. E., primary, Loustau, D., additional, and Delzon, S., additional
- Published
- 2002
- Full Text
- View/download PDF
19. Temperature response of parameters of a biochemically based model of photosynthesis. II. A review of experimental data
- Author
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Medlyn, B. E., primary, Dreyer, E., additional, Ellsworth, D., additional, Forstreuter, M., additional, Harley, P. C., additional, Kirschbaum, M. U. F., additional, Le Roux, X., additional, Montpied, P., additional, Strassemeyer, J., additional, Walcroft, A., additional, Wang, K., additional, and Loustau, D., additional
- Published
- 2002
- Full Text
- View/download PDF
20. Effects of elevated [CO2] on photosynthesis in European forest species: a meta-analysis of model parameters
- Author
-
Medlyn, B. E., primary, Badeck, F. -W., additional, De Pury, D. G. G., additional, Barton, C. V. M., additional, Broadmeadow, M., additional, Ceulemans, R., additional, De Angelis, P., additional, Forstreuter, M., additional, Jach, M. E., additional, Kellomäki, S., additional, Laitat, E., additional, Marek, M., additional, Philippot, S., additional, Rey, A., additional, Strassemeyer, J., additional, Laitinen, K., additional, Liozon, R., additional, Portier, B., additional, Roberntz, P., additional, Wang, K., additional, and Jstbid, P. G., additional
- Published
- 1999
- Full Text
- View/download PDF
21. Optimal stomatal conductance in relation to photosynthesis in climatically contrasting Eucalyptus species under drought.
- Author
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HÉROULT, ARNAUD, LIN, YAN‐SHIH, BOURNE, AIMEE, MEDLYN, BELINDA E., and ELLSWORTH, DAVID S.
- Subjects
STOMATA ,PHOTOSYNTHESIS ,DROUGHT tolerance ,EUCALYPTUS ,CARBON dioxide content of plants ,GAS exchange in plants ,PLANT cells & tissues - Abstract
ABSTRACT Models of stomatal conductance ( g
s ) are based on coupling between gs and CO2 assimilation ( Anet ), and it is often assumed that the slope of this relationship (' g1 ') is constant across species. However, if different plant species have adapted to different access costs of water, then there will be differences in g1 among species. We hypothesized that g1 should vary among species adapted to different climates, and tested the theory and its linkage to plant hydraulics using four Eucalyptus species from different climatic origins in a common garden. Optimal stomatal theory predicts that species from sub-humid zones have a lower marginal water cost of C gain, hence lower g1 than humid-zone species. In agreement with the theory that g1 is related to tissue carbon costs for water supply, we found a relationship between wood density and g1 across Eucalyptus species of contrasting climatic origins. There were significant reductions in the parameter g1 during drought in humid but not sub-humid species, with the latter group maintaining g1 in drought. There are strong differences in stomatal behaviour among related tree species in agreement with optimal stomatal theory, and these differences are consistent with the economics involved in water uptake and transport for carbon gain. [ABSTRACT FROM AUTHOR]- Published
- 2013
- Full Text
- View/download PDF
22. A mechanistic analysis of light and carbon use efficiencies.
- Author
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Medlyn, McMurtrie, and Dewar
- Subjects
- *
PLANTS , *CARBON dioxide , *ATMOSPHERIC carbon dioxide - Abstract
We explore the extent to which a simple mechanistic model of short-term plant carbon (C) dynamics can account for a number of generally observed plant phenomena. For an individual, fully expanded leaf, the model predicts that the fast-turnover labile C, starch and protein pools are driven into an approximate or moving steady state that is proportional to the average leaf absorbed irradiance on a time-scale of days to weeks, even under realistic variable light conditions, in qualitative agreement with general patterns of leaf acclimation to light observed both temporally within the growing season and spatially within plant canopies. When the fast-turnover pools throughout the whole plant (including stems and roots) also follow this moving steady state, the model predicts that the time-averaged whole-plant net primary productivity is proportional to the time-averaged canopy absorbed irradiance and to gross canopy photosynthesis, and thus suggests a mechanistic explanation of the observed approximate constancy of plant light-use efficiency (LUE) and carbon-use efficiency. Under variable light conditions, the fast-turnover pool sizes and the LUE are predicted to depend negatively on the coefficient of variation of irradiance. We also show that the LUE has a maximum with respect to the fraction of leaf labile C allocated to leaf protein synthesis (alp), reflecting a trade-off between leaf photosynthesis and leaf respiration. The optimal value of alp is predicted to decrease at elevated [CO2]a, suggesting an adaptive interpretation of leaf acclimation to CO2. The model therefore brings together a number of empirical observations within a common mechanistic framework. [ABSTRACT FROM AUTHOR]
- Published
- 1998
23. Modelling forest response to increasing CO2 concentration under nutrient-limited conditions.
- Author
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Kirschbaum, M. U. F., King, D. A., Comins, H. N., Mcmurtrie, R. E., Medlyn, B. E., Pongracic, S., Murty, D., Keith, H., Raison, R. J., Khanna, P. K., and Sheriff, D. W.
- Subjects
CARBON dioxide ,FORESTS & forestry ,MATHEMATICAL models ,PLANT nutrients ,WOODY plants ,PLANT growth ,PHOTOSYNTHESIS ,CARBON ,ECOLOGY - Abstract
The growth rates of woody plants depend on both the rate of photosynthetic carbon gain and the availability of essential nutrients. Instantaneous carbon gain is known to increase in response to increasing atmospheric CO
2 concentration, but it is uncertain whether this will translate into increased growth in the longer term under nutrient-limited conditions. An analytical model to address this question was developed by Comins & McMurtrie (1993, Ecological Applications 3,666-681). Their model was further tested and analysed. Manipulation of various assumptions in the model revealed its key assumptions and allowed a more confident prediction of expected growth responses to CO2 enrichment under nutrient-limited conditions. The analysis indicated that conclusions about the CO2 sensitivity of production were strongly influenced by assumptions about the relationship between foliar and heartwood nitrogen concentrations. With heartwood nitrogen concentration proportional to foliar nitrogen concentration, the model predicted a strong response of plant productivity to increasing CO2 concentration, whereas with heartwood nitrogen concentration set constant, the model predicted only a very slight growth response to changing CO2 concentration. On the other hand, predictions were only slightly affected by: (1) assumptions about the extent of nitrogen retranslocation out of senescing roots and foliage or wood during heartwood formation; (2) the effects of nitrogen status on specific leaf area or (3) leaf longevity; (4) carbon allocation between different plant parts; or (5) changes in the N:C ratio of organic matter sequestered in the passive pool of soil organic matter. Modification of the effect of foliar nitrogen concentration on the light utilization coefficient had only a small effect on the CO2 sensitivity for pines. However, this conclusion was strongly dependent on the chosen relationship between single-leaf photosynthesis and leaf nitrogen concentration. Overall, the analysis suggested that trees growing under nitrogen-limited conditions can respond to increasing atmospheric CO2 concentration with considerable increases in growth. [ABSTRACT FROM AUTHOR]- Published
- 1994
- Full Text
- View/download PDF
24. Effects of elevated [CO[sub 2]] on photosynthesis in European forest species: a meta-analysis of model parameters.
- Author
-
Medlyn, B. E., Badeck, F. -W., De Pury, D. G. G., Barton, C. V. M., Broadmeadow, M., Ceulemans, R., De Angelis, P., Forstreuter, M., Jach, M. E., Kellomäki, S., Laitat, E., Marek, M., Philippot, S., Rey, A., Strassemeyer, J., Laitinen, K., Liozon, R., Portier, B., Roberntz, P., and Wang, K.
- Subjects
- *
PHYSIOLOGICAL effects of carbon dioxide , *PHOTOSYNTHESIS , *META-analysis - Abstract
Analyzes the effect of elevated carbon dioxide concentration on photosynthesis in European forest species using meta-analysis techniques. Relationship between the down-regulation of photosynthesis and poor nutrient status or accumulation of starch; Induction of nutrient limitation by carbon availability.
- Published
- 1999
- Full Text
- View/download PDF
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