Scaling up of leaf stomatal resistance as a function of photosynthetic photon flux density

This study presents a combined approach to scale up leaf stomatal resistance (r_L) to canopy resistance (r_c). We integrated several methodologies and demonstrated a successful application of an approach to scale up r_L to r_c for subsurface drip-irrigated field corn (Zea mays L). We scaled up r_L using measured photosynthetic photon flux density (PPFD) as the main driver. PPFD alone was able to explain 85% of the variability in r_c. The average root mean square difference between the measured and estimated r_c was 11.1 s m^-1. Results are very encouraging as the PPFD versus r_c approach to scale up the r_L to r_c does not account for other variables such as vapor pressure deficit, carbon dioxide concentration, wind speed, and soil evaporation. This integration and application of scaling up approach should aid to our understanding of the r_c-PPFD relationships and dynamics of the soil-canopy-atmosphere continuum and contribute to better estimate evaporative losses from plant communities using one-step approach.