Global diurnal and nocturnal parameters of stomatal conductance in woody plants and major crops

Abstract

Aim Stomata regulate CO2 uptake, water‐vapour loss and uptake of gaseous pollutants. Jarvis‐type models that apply multiple‐constraint functions are commonly used to estimate stomatal conductance (gs), but most parameters for plant functional types (PFTs) have been estimated using limited information. We refined the data set of key components of the gs response to environmental factors in global PFTs. Location Global. Time period Data published in 1973–2015. Major taxa studied Woody plants and major crops (rice, wheat and maize). Methods We reviewed 235 publications of field‐observed gs for the parameterization of Jarvis‐type models in global PFTs. The relationships between stomatal parameters and climatic factors [mean annual air temperature (MAT) and mean annual precipitation (MAP)] were assessed. Results We found that maximal stomatal conductance (gmax) in global woody plants was correlated with MAP rather than with MAT. The gmax of woody plants on average increased from 0.18 to 0.26 mol/m2/s with an increase in MAP from 0 to 2,000 mm. Models, however, can use a single gmax across major crops (0.44 mol/m2/s). We propose similar stomatal responses to light for C3 crops and woody plants, but C4 crops should use a higher light saturation point of gs. Stomatal sensitivity to vapour‐pressure deficit (VPD) was similar across forest PFTs and crops, although desert shrubs had a relatively low sensitivity of stomata to VPD. The optimal temperature for gs increased by 1 °C for every 3.0 °C of MAT. Stomatal sensitivity to predawn water potential was reduced in hot and dry climate. The fraction of nighttime conductance to gmax (0.14 for forest trees, 0.28 for desert shrubs and 0.13 for crops) should be incorporated into the models. Main conclusions This analysis of global gs data provides a new summary of gs responses and will contribute to modelling studies for plant–atmosphere gas exchange and land‐surface energy partitioning.

Plant Hydraulic Stress Strategy Improves Model Predictions of the Response of Gross Primary Productivity to Drought Across China

“…The limited improvement might be related to the poor representation of plant stomatal behaviors for both PHS and SMS configurations in LSMs (Grossiord et al, 2020; Medlyn et al, 2016). For example, nighttime stomatal conductance and nighttime transpiration were reported to be unneglectable in a wide range of plants in multiple climate zones (Hoshika et al, 2018; Yu et al, 2019). Moreover, significant nighttime stomatal conductance was shown to be a strategy to keep water resources close to an individual plant rather than moving that water toward neighboring competitors (Huang et al, 2017; Yu, Feng, et al, 2018).…”

Equivalence of foliar water uptake and stomatal conductance?

“…Because relative humidity has a water potential equivalent (e.g., 100% RH = 0 MPa, and 95% RH = −6.8 MPa at 20°C, Figure ), it is possible to express g s in the same units as K FWU (becoming g Ψ ) by substituting D in Equation for the water potential of the air (Ψ a ) making the two values directly comparable (see the Supporting Information for discussion of the limitations of expressing humidity as water potential): where Ψ a is derived by (Pickard, ; Spanner, ) R is the universal gas constant (8.13 J mol −1 K −1 ), T is the temperature (K), V w is the molar volume of liquid water (1.80 × 10 −5 m 3 mol −1 ), and 10 6 is a conversion factor to express units in MPa. Thus, by combining Equations –, we can convert the units of g s to normalize by water potential difference ( g ψ , mmol m −2 s −1 MPa −1 ): In a recent meta‐analysis, Hoshika, Osada, de Marco, Peñuelas, and Paoletti () found that g max ranged from 70 to 360 mmol m −2 s −1 in woody plants and up to 610 mmol m −2 s −1 in crop plants, which is equivalent to g ψ values of 0.010, 0.053, and 0.090 mmol m −2 s −1 MPa −1 , respectively (assuming g s values measured at an average of 20°C and 70% RH, see the Supporting Information for sensitivity analysis). This range overlaps with the reported values for K FWU listed above, showing that the measured FWU could have been partially or wholly due to vapour uptake (i.e., − E , Figure ).…”

Phylogenetic and biogeographic controls of plant nighttime stomatal conductance

“…Hoshika et al . () compiled a large dataset to show the correlation between daytime maximum g s in woody plants and mean annual precipitation (MAP), but the information of climatic (biogeographic) controls on g sn is limited.…”

“…Although Lombardozzi et al (2017) compiled a large dataset (n = 204) to better represent g sn in land surface models and allow the comparison of g sn among different functional groups, these observed g sn values were estimated by a variety of methods and measurement conditions, which limits rigorous comparison across functional groups, and had very limited information on boreal climate zones. Hoshika et al (2018) compiled a large dataset to show the correlation between daytime maximum g s in woody plants and mean annual precipitation (MAP), but the information of climatic (biogeographic) controls on g sn is limited.…”