Incorporating non-stomatal limitation improves the performance of leaf and canopy models at high vapour pressure deficit

J. Yang; R. A. Duursma; M. G. De Kauwe; D. Kumarathunge; M. Jiang; K. Mahmud; T. E. Gimeno; K. Y. Crous; D. S. Ellsworth; J. Peters; B. Choat; D. Eamus; B. E. Medlyn

doi:10.1093/treephys/tpz103

Incorporating non-stomatal limitation improves the performance of leaf and canopy models at high vapour pressure deficit

J. Yang^*, R. A. Duursma, M. G. De Kauwe, D. Kumarathunge, M. Jiang, K. Mahmud, T. E. Gimeno, K. Y. Crous, D. S. Ellsworth, J. Peters, B. Choat, D. Eamus, B. E. Medlyn

^*Corresponding author for this work

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Abstract

Vapour pressure deficit (D) is projected to increase in the future as temperature rises. In response to increased D, stomatal conductance (g_s) and photosynthesis (A) are reduced, which may result in significant reductions in terrestrial carbon, water and energy fluxes. It is thus important for gas exchange models to capture the observed responses of g_s and A with increasing D. We tested a series of coupled A-g_s models against leaf gas exchange measurements from the Cumberland Plain Woodland (Australia), where D regularly exceeds 2 kPa and can reach 8 kPa in summer. Two commonly used A-g_s models were not able to capture the observed decrease in A and g_s with increasing D at the leaf scale. To explain this decrease in A and g_s, two alternative hypotheses were tested: hydraulic limitation (i.e., plants reduce g_s and/or A due to insufficient water supply) and non-stomatal limitation (i.e., downregulation of photosynthetic capacity). We found that the model that incorporated a non-stomatal limitation captured the observations with high fidelity and required the fewest number of parameters. Whilst the model incorporating hydraulic limitation captured the observed A and g_s, it did so via a physical mechanism that is incorrect. We then incorporated a non-stomatal limitation into the stand model, MAESPA, to examine its impact on canopy transpiration and gross primary production. Accounting for a non-stomatal limitation reduced the predicted transpiration by ~19%, improving the correspondence with sap flow measurements, and gross primary production by ~14%. Given the projected global increases in D associated with future warming, these findings suggest that models may need to incorporate non-stomatal limitation to accurately simulate A and g_s in the future with high D. Further data on non-stomatal limitation at high D should be a priority, in order to determine the generality of our results and develop a widely applicable model.

Original language	English
Pages (from-to)	1961-1974
Number of pages	14
Journal	Tree Physiology
Volume	39
Issue number	12
DOIs	https://doi.org/10.1093/treephys/tpz103
Publication status	Published - 1 Dec 2019

Bibliographical note

Funding Information:
J.Y. was supported by a PhD scholarship from Hawkesbury Institute for the Environment, Western Sydney University. M.G.D.K. acknowledges funding from the Australian Research Council (ARC) Centre of Excellence for Climate Extremes (CE170100023), the ARC Discovery Grant (DP190101823) and support from the NSW Research Attraction and Acceleration Program. EucFACE was built as an initiative of the Australian Government as part of the Nation-building Economic Stimulus Package and is supported by the Australian Commonwealth in collaboration with Western Sydney University. It is also part of a Terrestrial Ecosystem Research Network Super-site facility.

Publisher Copyright:
© 2019 The Author(s) 2019. Published by Oxford University Press. All rights reserved.

Keywords

hydraulic limitation
model-data assimilation
photosynthesis
stomatal conductance

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Yang, J., Duursma, R. A., De Kauwe, M. G., Kumarathunge, D., Jiang, M., Mahmud, K., Gimeno, T. E., Crous, K. Y., Ellsworth, D. S., Peters, J., Choat, B., Eamus, D., & Medlyn, B. E. (2019). Incorporating non-stomatal limitation improves the performance of leaf and canopy models at high vapour pressure deficit. Tree Physiology, 39(12), 1961-1974. https://doi.org/10.1093/treephys/tpz103

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abstract = "Vapour pressure deficit (D) is projected to increase in the future as temperature rises. In response to increased D, stomatal conductance (gs) and photosynthesis (A) are reduced, which may result in significant reductions in terrestrial carbon, water and energy fluxes. It is thus important for gas exchange models to capture the observed responses of gs and A with increasing D. We tested a series of coupled A-gs models against leaf gas exchange measurements from the Cumberland Plain Woodland (Australia), where D regularly exceeds 2 kPa and can reach 8 kPa in summer. Two commonly used A-gs models were not able to capture the observed decrease in A and gs with increasing D at the leaf scale. To explain this decrease in A and gs, two alternative hypotheses were tested: hydraulic limitation (i.e., plants reduce gs and/or A due to insufficient water supply) and non-stomatal limitation (i.e., downregulation of photosynthetic capacity). We found that the model that incorporated a non-stomatal limitation captured the observations with high fidelity and required the fewest number of parameters. Whilst the model incorporating hydraulic limitation captured the observed A and gs, it did so via a physical mechanism that is incorrect. We then incorporated a non-stomatal limitation into the stand model, MAESPA, to examine its impact on canopy transpiration and gross primary production. Accounting for a non-stomatal limitation reduced the predicted transpiration by ~19%, improving the correspondence with sap flow measurements, and gross primary production by ~14%. Given the projected global increases in D associated with future warming, these findings suggest that models may need to incorporate non-stomatal limitation to accurately simulate A and gs in the future with high D. Further data on non-stomatal limitation at high D should be a priority, in order to determine the generality of our results and develop a widely applicable model.",

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author = "J. Yang and Duursma, {R. A.} and {De Kauwe}, {M. G.} and D. Kumarathunge and M. Jiang and K. Mahmud and Gimeno, {T. E.} and Crous, {K. Y.} and Ellsworth, {D. S.} and J. Peters and B. Choat and D. Eamus and Medlyn, {B. E.}",

note = "Funding Information: J.Y. was supported by a PhD scholarship from Hawkesbury Institute for the Environment, Western Sydney University. M.G.D.K. acknowledges funding from the Australian Research Council (ARC) Centre of Excellence for Climate Extremes (CE170100023), the ARC Discovery Grant (DP190101823) and support from the NSW Research Attraction and Acceleration Program. EucFACE was built as an initiative of the Australian Government as part of the Nation-building Economic Stimulus Package and is supported by the Australian Commonwealth in collaboration with Western Sydney University. It is also part of a Terrestrial Ecosystem Research Network Super-site facility. Publisher Copyright: {\textcopyright} 2019 The Author(s) 2019. Published by Oxford University Press. All rights reserved.",

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doi = "10.1093/treephys/tpz103",

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Yang, J, Duursma, RA, De Kauwe, MG, Kumarathunge, D, Jiang, M, Mahmud, K, Gimeno, TE, Crous, KY, Ellsworth, DS, Peters, J, Choat, B, Eamus, D & Medlyn, BE 2019, 'Incorporating non-stomatal limitation improves the performance of leaf and canopy models at high vapour pressure deficit', Tree Physiology, vol. 39, no. 12, pp. 1961-1974. https://doi.org/10.1093/treephys/tpz103

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AU - Duursma, R. A.

AU - De Kauwe, M. G.

AU - Kumarathunge, D.

AU - Jiang, M.

AU - Mahmud, K.

AU - Gimeno, T. E.

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AU - Peters, J.

AU - Choat, B.

AU - Eamus, D.

AU - Medlyn, B. E.

N1 - Funding Information: J.Y. was supported by a PhD scholarship from Hawkesbury Institute for the Environment, Western Sydney University. M.G.D.K. acknowledges funding from the Australian Research Council (ARC) Centre of Excellence for Climate Extremes (CE170100023), the ARC Discovery Grant (DP190101823) and support from the NSW Research Attraction and Acceleration Program. EucFACE was built as an initiative of the Australian Government as part of the Nation-building Economic Stimulus Package and is supported by the Australian Commonwealth in collaboration with Western Sydney University. It is also part of a Terrestrial Ecosystem Research Network Super-site facility. Publisher Copyright: © 2019 The Author(s) 2019. Published by Oxford University Press. All rights reserved.

PY - 2019/12/1

Y1 - 2019/12/1

N2 - Vapour pressure deficit (D) is projected to increase in the future as temperature rises. In response to increased D, stomatal conductance (gs) and photosynthesis (A) are reduced, which may result in significant reductions in terrestrial carbon, water and energy fluxes. It is thus important for gas exchange models to capture the observed responses of gs and A with increasing D. We tested a series of coupled A-gs models against leaf gas exchange measurements from the Cumberland Plain Woodland (Australia), where D regularly exceeds 2 kPa and can reach 8 kPa in summer. Two commonly used A-gs models were not able to capture the observed decrease in A and gs with increasing D at the leaf scale. To explain this decrease in A and gs, two alternative hypotheses were tested: hydraulic limitation (i.e., plants reduce gs and/or A due to insufficient water supply) and non-stomatal limitation (i.e., downregulation of photosynthetic capacity). We found that the model that incorporated a non-stomatal limitation captured the observations with high fidelity and required the fewest number of parameters. Whilst the model incorporating hydraulic limitation captured the observed A and gs, it did so via a physical mechanism that is incorrect. We then incorporated a non-stomatal limitation into the stand model, MAESPA, to examine its impact on canopy transpiration and gross primary production. Accounting for a non-stomatal limitation reduced the predicted transpiration by ~19%, improving the correspondence with sap flow measurements, and gross primary production by ~14%. Given the projected global increases in D associated with future warming, these findings suggest that models may need to incorporate non-stomatal limitation to accurately simulate A and gs in the future with high D. Further data on non-stomatal limitation at high D should be a priority, in order to determine the generality of our results and develop a widely applicable model.

AB - Vapour pressure deficit (D) is projected to increase in the future as temperature rises. In response to increased D, stomatal conductance (gs) and photosynthesis (A) are reduced, which may result in significant reductions in terrestrial carbon, water and energy fluxes. It is thus important for gas exchange models to capture the observed responses of gs and A with increasing D. We tested a series of coupled A-gs models against leaf gas exchange measurements from the Cumberland Plain Woodland (Australia), where D regularly exceeds 2 kPa and can reach 8 kPa in summer. Two commonly used A-gs models were not able to capture the observed decrease in A and gs with increasing D at the leaf scale. To explain this decrease in A and gs, two alternative hypotheses were tested: hydraulic limitation (i.e., plants reduce gs and/or A due to insufficient water supply) and non-stomatal limitation (i.e., downregulation of photosynthetic capacity). We found that the model that incorporated a non-stomatal limitation captured the observations with high fidelity and required the fewest number of parameters. Whilst the model incorporating hydraulic limitation captured the observed A and gs, it did so via a physical mechanism that is incorrect. We then incorporated a non-stomatal limitation into the stand model, MAESPA, to examine its impact on canopy transpiration and gross primary production. Accounting for a non-stomatal limitation reduced the predicted transpiration by ~19%, improving the correspondence with sap flow measurements, and gross primary production by ~14%. Given the projected global increases in D associated with future warming, these findings suggest that models may need to incorporate non-stomatal limitation to accurately simulate A and gs in the future with high D. Further data on non-stomatal limitation at high D should be a priority, in order to determine the generality of our results and develop a widely applicable model.

KW - hydraulic limitation

KW - model-data assimilation

KW - photosynthesis

KW - stomatal conductance

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DO - 10.1093/treephys/tpz103

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AN - SCOPUS:85078463557

SN - 0829-318X

VL - 39

SP - 1961

EP - 1974

JO - Tree Physiology

JF - Tree Physiology

IS - 12

ER -

Incorporating non-stomatal limitation improves the performance of leaf and canopy models at high vapour pressure deficit

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Bibliographical note

Keywords

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