Table 1.
Species included in the study, their Akaike information criterion (AIC) values and R2 values during model selection.
Species with no values were not included in the model selection analyses because photosynthesis was not measured directly (but were included in the RandomForest analyses). In AIC values, bolded values indicate that a given model for a species was the most likely (delta-AIC > 3) for that species. Models include the Medlyn (M), Ball-Berry-Leuning (BBL), Ball-Berry-Leuning with hydraulic addition (BBL.H) and Tuzet (T) models (see Methods).
Fig 1.
Partial dependency of stomatal conductance (gs) on measured leaf water potential (ψleaf) in (a) temperate gymnosperm species, (b) temperate angiosperm species, (c) tropical deciduous species, and (d) tropical evergreen species.
Y-axis values are scaled from 0–1 by the percentage of stomatal closure reached. Species codes are the first two letters of the genus and the first two letters of the species from Table A in S1 File.
Fig 2.
(a) Relationship across species between the water potential at which 50% of stomatal conductance is lost (ψgs50) and the water potential at which 50% of stem hydraulic conductance (ψx50) is lost. Black line is the 1:1 line and red the OLR regression best fit. (b) Histogram of the percent loss of stem hydraulic conductance (PLC) at the water potential at which 50% of stomatal conductance is lost (ψgs50).
Fig 3.
(a) Akaike Information Criterion (AIC) value average across all 24 species for the Medlyn (M), Ball-Berry-Leuning (BBL), Ball-Berry-Leuning plus Hydraulics (BBL.H), and Tuzet (T) stomatal conductance models. (b) Frequency of species’ delta-AIC values between the BBL and M models. (c) Frequency of species’ delta-AIC values between the BBLH and M models. (d) Frequency of species’ delta-AIC values between the T and M models. In each of (b-d), the top number is the mean delta-AIC across all species and the lower number is the median delta-AIC.
Fig 4.
(a) Root mean squared error (RMSE) and (e) OLS regression R2 between predicted and observed stomatal conductance averaged across all 24 species for the Medlyn (M), Ball-Berry-Leuning (BBL), Ball-Berry-Leuning plus Hydraulics (BBL.H), and Tuzet (T) stomatal conductance models. (b and f) Frequency of species’ % improvement in RMSE and R2 respectively between the BBL and M models. (c and g) Frequency of species’ % improvement in RMSE and R2 respectively between the BBLH and M models. (d and h) Frequency of species’ % improvement in RMSE and R2 respectively between the T and M models.
Fig 5.
(a) Slope between the residuals of observed versus predicted stomatal conductance and leaf temperature (Tleaf), (b) vapor pressure deficit (VPD), and (c) soil water potential (PsiS).
Negative values in the Tleaf and VPD plots indicate over-prediction of gs during dry conditions (high Tleaf and high VPD), whereas positive values in the PsiS plot indicates over-prediction of gs during dry conditions. Models are Medlyn (red), Ball-Berry-Leuning (darkred), Ball-Berry-Leuning plus the hydraulic term (blue) and Tuzet (green). Error bars are +/- 1 S.E.
Fig 6.
Histogram of species’ percent bias in prediction of stomatal conductance at the 10th percentile of soil water potential.
Negative numbers mean over-prediction of gs by models compared to measured values. Solid line is the mean across species and dashed line the median. Models are (a) Medlyn model, (b) Ball-Berry-Leuning model, (c) Ball-Berry-Leuning plus Hydraulics model, and (d) Tuzet model.