Short-term variation in leaf-level water use efficiency in a tropical forest

Area of Science:

• Plant physiology
• Ecosystem modeling
• Global change biology

Background:

• Stomatal regulation of transpiration and CO2 assimilation is critical for forecasting terrestrial ecosystem responses to global change.
• Accurate and mechanistic model representation of stomatal conductance (gs) and assimilation is crucial for understanding forest productivity and climate relationships.

Purpose of the Study:

• To assess physiological and mechanistic controls on stomatal slope (g1) and stomatal intercept (g0) parameters.
• To improve the accuracy of modeled stomatal conductance (gs) by accounting for diurnal and measurement approach variations.

Main Methods:

• Utilized diurnal gas exchange surveys and leaf-level response curves from six tropical broadleaf evergreen tree species.
• Compared g1 estimations from ex situ response curves versus survey data.
• Analyzed variations in g0 and g1 across different phenological stages and diurnal periods.

Main Results:

• g1 estimated from ex situ response curves was 50% lower than that from survey data.
• g0 and g1 showed variation with leaf phenology, but this trend was not consistent across species.
• A diurnal trend in g1 and g0 was identified, significantly improving model projections of diurnal transpiration.

Conclusions:

• Accounting for diurnal variation in stomatal behavior and measurement approaches enhances modeled gs accuracy.
• Phenological variation in stomatal behavior is less critical than diurnal variation for improving land-surface models.
• Further research into the mechanisms driving diurnal variation in g1 is needed for comprehensive land-surface modeling.