TY - JOUR

T1 - Combining the [ABA] and net photosynthesis-based model equations of stomatal conductance

AU - Huntingford, Chris

AU - Smith, D. Mark

AU - Davies, William John

AU - Falk, Richard

AU - Sitch, Stephen

AU - Mercado, Lina M.

PY - 2015/3/24

Y1 - 2015/3/24

N2 - Stomatal conductance gs is variously depicted as being dependent on environmental conditions (Jarvis, 976), transpiration (Monteith, 1995), net photosynthesis (Leuning, 1995) or chemical signalling arriving in the xylem (Tardieu and Davies, 1993). Accurate descriptions of gs are being increasingly demanded in the large-scale land surface model components of General Circulation Models (GCMs) to predict future land-atmospheric fluxes of water vapour, heat and carbon dioxide. The JULES model, for instance, uses the net photosynthesis description combined with a relatively simple semi-linear dependence on soil moisture content that modulates the photosynthesis dependence (Cox et al., 1998).Dewar (2002) combines the Leuning (1995) and Tardieu and Davies (1993) models. We revisit that combination, and discuss whether the Vapour Pressure Deficit (VPD) implicit in both components is different or in common. Further, we show a potential re-arrangement of the combined equations reveals that this model for gs can be considered as being dependent on only four variables: evaporative flux Jw, net photosynthesis an, soil moisture content θ and ambient CO2 concentration ca. Expressed this way, gs is influenced by two relatively slowly varying stores of the hydrological and carbon cycles (soil water content and atmospheric CO2) and two more rapidly fluctuating fluxes from both cycles (evaporation and net photosynthesis).We consider how the modelling structure and its response to both canopy-level and soil environmental controls may make it suitable for inclusion in GCMs, and what this entails in terms of parameterisation.

AB - Stomatal conductance gs is variously depicted as being dependent on environmental conditions (Jarvis, 976), transpiration (Monteith, 1995), net photosynthesis (Leuning, 1995) or chemical signalling arriving in the xylem (Tardieu and Davies, 1993). Accurate descriptions of gs are being increasingly demanded in the large-scale land surface model components of General Circulation Models (GCMs) to predict future land-atmospheric fluxes of water vapour, heat and carbon dioxide. The JULES model, for instance, uses the net photosynthesis description combined with a relatively simple semi-linear dependence on soil moisture content that modulates the photosynthesis dependence (Cox et al., 1998).Dewar (2002) combines the Leuning (1995) and Tardieu and Davies (1993) models. We revisit that combination, and discuss whether the Vapour Pressure Deficit (VPD) implicit in both components is different or in common. Further, we show a potential re-arrangement of the combined equations reveals that this model for gs can be considered as being dependent on only four variables: evaporative flux Jw, net photosynthesis an, soil moisture content θ and ambient CO2 concentration ca. Expressed this way, gs is influenced by two relatively slowly varying stores of the hydrological and carbon cycles (soil water content and atmospheric CO2) and two more rapidly fluctuating fluxes from both cycles (evaporation and net photosynthesis).We consider how the modelling structure and its response to both canopy-level and soil environmental controls may make it suitable for inclusion in GCMs, and what this entails in terms of parameterisation.

KW - Stomatal conductance

KW - ABA

KW - Soil moisture

KW - Terrestrial carbon cycle

KW - General circulation models

KW - Climate change

U2 - 10.1016/j.ecolmodel.2015.01.005

DO - 10.1016/j.ecolmodel.2015.01.005

M3 - Journal article

VL - 300

SP - 81

EP - 88

JO - Ecological Modelling

JF - Ecological Modelling

SN - 0304-3800

ER -