Using Canopy Resistance for Infrared Heater Control When Warming Open-Field Plots

To simulate future global warming, several research groups use arrays of infrared heaters to warm open-field plots with a control strategy that involves maintaining a constrat rise in canopy temperatures of the Heated plots above those of un-heated Reference plots. However, if the warming treatment itself alters canopy architecture, plant physiology, albedo or other plot characteristics in ways that affect the energy balances of the heated plots so as to make them materially different from those of the Reference plots, then the Reference plots no longer are proper references against which to determine a desired canopy temperature rise. Herein, a novel alternative control strategy is proposed whereby plant and air temperature and other micro-climate measurements are used to determine the canopy resistances of the Heated plots, which in turn are used to calculate the amount of infrared radiation that is needed to achieve the desired rise in canopy temperature. Then the voltage supplied to the heaters can be modulated accordingly to attain this temperature rise.