Plant profit maximization improves predictions of European forest responses to drought
Date
2020-01-27
Authors
Sabot, Manon E. B.
De Kauwe, Martin G.
Pitman, Andy J.
Medlyn, Belinda E.
Verhoef, Anne
Abramowitz, Gab
Ukkola, Anna
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Cambridge University Press
Abstract
Knowledge of how water stress impacts the carbon and water cycles is a key uncertainty in terrestrial biosphere models. We tested a new profit maximization model, where photosynthetic uptake of CO2 is optimally traded against plant hydraulic function, as an alternative to the empirical functions commonly used in models to regulate gas exchange during periods of water stress. We conducted a multi-site evaluation of this model at the ecosystem scale, before and during major droughts in Europe. Additionally, we asked whether the maximum hydraulic conductance in the soil-plant continuum k(max) (a key model parameter which is not commonly measured) could be predicted from long-term site climate. Compared with a control model with an empirical soil moisture function, the profit maximization model improved the simulation of evapotranspiration during the growing season, reducing the normalized mean square error by c. 63%, across mesic and xeric sites. We also showed that k(max) could be estimated from long-term climate, with improvements in the simulation of evapotranspiration at eight out of the 10 forest sites during drought. Although the generalization of this approach is contingent upon determining k(max), it presents a mechanistic trait-based alternative to regulate canopy gas exchange in global models.
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Keywords
canopy gas exchange, hydraulic trait adjustments to climate, land surface models, plant optimality, plant profit maximization, plant trait coordination, vegetation drought responses
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Source
New Phytologist
Type
Journal article
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Open Access
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