Estimating Bulk Stomatal Conductance in Grapevine Canopies.

Area of Science:

• Plant Physiology
• Agricultural Science
• Environmental Science

Background:

• Grapevines regulate water transport (transpiration) via physiological mechanisms affecting water flow through the soil-plant-atmosphere continuum.
• Bulk stomatal conductance (canopy scale) varies with environmental factors like vapor pressure deficit, radiation, and water availability.

Purpose of the Study:

• To present a simplified method for determining bulk stomatal conductance in grapevines.
• To facilitate future characterization of dynamic stomatal responses in vineyard ecosystems.
• To improve water use modeling in vineyards by accurately estimating canopy transpiration.

Main Methods:

• Utilized the Shuttleworth and Wallace crop canopy energy flux model.
• Employed measurements of individual vine sap flow, canopy microclimate (temperature, humidity), and absorbed net radiation.
• Avoided complex measurements like soil heat flux and boundary layer conductance, simplifying vineyard management.

Main Results:

• Successfully estimated bulk stomatal conductance at 15-minute intervals in a non-irrigated Bordeaux vineyard.
• Observed significant diurnal variations and seasonal decreases in conductance linked to vine water stress (measured by predawn leaf water potential).
• Sensitivity analysis identified transpiration flux and vapor pressure deficit as key drivers of stomatal conductance.

Conclusions:

• The presented method offers a practical approach to measure bulk stomatal conductance in open-canopy vineyards.
• Accurate characterization of bulk stomatal conductance is crucial for modeling vine transpiration and water use.
• This research aids in understanding and managing grapevine water status and optimizing irrigation strategies.