Analysis of scaling-up resistances from leaf to canopy using numerical simulations
A multi-layer model, combining Lagrangian dispersion at the canopy level with Ohm's Law analogy at the leaf level, was used in numerical simulations to assess the leaf-to-canopy scale translation of surface resistances. The model produced unique profiles of fluxes and scalar concentrations that satisfied both the dispersion and leaf models. Environmental factors and canopy architecture were varied, and stomatal conductance was simulated using either a simple relationship with net radiation or the Ball and Berry model to account for feedback mechanisms. Results showed that, when the assumptions of the Penman–Monteith equation were met, scaled-up leaf conductance closely matched the bulk canopy conductance. However, as the scenarios modeled departed from the ideal conditions of Penman–Monteith, the agreement decreased. In particular, correct estimation of the aerodynamic resistance, through correct parameterization of the roughness length for sensible heat, was identified as a key issue.