Hydraulic theory predicts stomatal responses to climatic water deficits

Pragmatic hydraulic theory predicts stomatal responses to climatic water deficits

by Sperry J. S., Wang Y., Wolfe B. T., Mackay D. S., Anderegg W. R. L., McDowell N. G., Pockman W. T. (2016)

John Sperry, Yujie Wang, Brett Wolfe, D. Scott Mackay, William R L Anderegg, Nate McDowell, William Pockman,

Sperry JS1Wang Y2Wolfe BT3Mackay DS4Anderegg WR2McDowell NG5Pockman WT6.

1 Department of Biology, University of Utah, Salt Lake City, UT, 84112, USA.

2 Department of Biology, University of Utah, Salt Lake City, UT, 84112, USA.

3 Smithsonian Tropical Research Institute, PO Box 0843-03092, Balboa, Panama.

4 Department of Geography, State University of New York, Buffalo, NY, 14260, USA.

5 Earth and Environmental Sciences Division, Los Alamos National Lab, Los Alamos, NM, 87545, USA.

6 Biology Department, University of New Mexico, Albuquerque, NM, 87131, USA.

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In New Phytol. 212: 577–589 – DOI: 10.1111/nph.14059

https://www.ncbi.nlm.nih.gov/pubmed/27329266

Abstract

Ecosystem models have difficulty predicting plant drought responses, partially from uncertainty in the stomatal response to water deficits in soil and atmosphere.

We evaluate a ‘supply-demand’ theory for water-limited stomatal behavior that avoids the typical scaffold of empirical response functions. The premise is that canopy water demand is regulated in proportion to threat to supply posed by xylem cavitation and soil drying.

The theory was implemented in a trait-based soil-plant-atmosphere model. The model predicted canopy transpiration (E), canopy diffusive conductance (G), and canopy xylem pressure (Pcanopy ) from soil water potential (Psoil ) and vapor pressure deficit (D). Modeled responses to D and Psoil were consistent with empirical response functions, but controlling parameters were hydraulic traits rather than coefficients.

Maximum hydraulic and diffusive conductances and vulnerability to loss in hydraulic conductance dictated stomatal sensitivity and hence the iso- to anisohydric spectrum of regulation. The model matched wide fluctuations in G and Pcanopy across nine data sets from seasonally dry tropical forest and piñon-juniper woodland with < 26% mean error.

Promising initial performance suggests the theory could be useful in improving ecosystem models. Better understanding of the variation in hydraulic properties along the root-stem-leaf continuum will simplify parameterization

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A ‘supply-demand’ theory for water-limited stomatal behavior

 

Pragmatic hydraulic theory predicts stomatal responses to climatic water deficits

Sperry J. S., Wang Y., Wolfe B. T., Mackay D. S., Anderegg W. R. L., McDowell N. G., Pockman W. T. (2016)

University of Utahjohn_sperry

University of Utah, Salt Lake City, yujie_wang9

University of Utah, Salt Lake City, brett_wolfe2

University Buffalo, State University New Yorkd_mackay

University of Utah, Salt Lake City, william_anderegg

Nate G. McDowell,

University of New Mexicowilliam_pockman

 

–  – New Phytologist 2016 – DOI: 10.1111/nph.14059 –

https://www.researchgate.net/publication/304330127_Pragmatic_hydraulic_theory_predicts_stomatal_responses_to_climatic_water_deficits

Abstract
Ecosystem models have difficulty predicting plant drought responses, partially from uncertainty in the stomatal response to water deficits in soil and atmosphere.
We evaluate a ‘supply-demand’ theory for water-limited stomatal behavior that avoids the typical scaffold of empirical response functions. The premise is that canopy water demand is regulated in proportion to threat to supply posed by xylem cavitation and soil drying.
The theory was implemented in a trait-based soil-plant-atmosphere model. The model predicted canopy transpiration (E), canopy diffusive conductance (G), and canopy xylem pressure (Pcanopy ) from soil water potential (Psoil ) and vapor pressure deficit (D).
Modeled responses to D and Psoil were consistent with empirical response functions, but controlling parameters were hydraulic traits rather than coefficients. Maximum hydraulic and diffusive conductances and vulnerability to loss in hydraulic conductance dictated stomatal sensitivity and hence the iso- to anisohydric spectrum of regulation.
The model matched wide fluctuations in G and Pcanopy across nine data sets from seasonally dry tropical forest and piñon-juniper woodland with < 26% mean error.
Promising initial performance suggests the theory could be useful in improving ecosystem models. Better understanding of the variation in hydraulic properties along the root-stem-leaf continuum will simplify parameterization.