Canopy conductance, commonly denoted , is a dimensionless quantity characterizing radiation distribution in tree canopy. By definition, it is calculated as a ratio of daily water use to daily mean vapor pressure deficit (VPD). [1] Canopy conductance can be also experimentally obtained by measuring sap flow and environmental variables. [2] Stomatal conductance may be used as a reference value to validate the data, by summing the total stomatal conductance of all leaf classes within the canopy. [3]