Global diurnal and nocturnal parameters of stomatal conductance in woody plants and major crops. Issue 2 (6th December 2017) - Hoshika, Yasutomo
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 ( g s ), but most parameters for plant functional types (PFTs) have been estimated using limited information. We refined the data set of key components of the g s 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 g s 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 ( g max ) in global woody plants was correlated with MAP rather than with MAT. The g max of woody plants on average increased from 0.18 to 0.26 mol/m 2 /s with an increase in MAP from 0 to 2, 000 mm. Models, however, can use a single g max across major crops (0.44 mol/m 2 /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 g s . 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 g s 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 g max (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 g s data provides a new summary of g s responses and will contribute to modelling studies for plant–atmosphere gas exchange and land‐surface energy partitioning.