Simulating Potato Gas Exchange As Influenced by CO2 and Irrigation.

Recent research suggests that an energy balance approach is required for crop models to
adequately respond to current and future climatic conditions associated with elevated CO2,
higher temperatures, and water scarcity. More realistic models are needed in order to
understand the impact of, and develop adaptation strategies for, the effects of climate change
on agricultural production of important agronomic crops. SPUDSIM, a process-level potato crop
model developed by USDA-ARS, couples sub-models for leaf photosynthetic rate, stomatal
conductance, and an energy balance at the leaf surface and then scales the gas exchange
predictions to the whole canopy using a sunlit/shaded leaf area approach in order to simulate
diurnal responses to air temperature, radiation, CO2, humidity and other microclimate factors.
SPUDSIM was linked with 2DSOIL, a two-dimensional soils model that simulates root growth,
water, and nutrient uptake. A hydraulic stomatal control algorithm, linked to leaf water
potential, was recently incorporated into the model to account for plant water status effects
on stomatal closure. The current research evaluates the ability of the model to respond to
varying irrigation regimes (10, 25, 50, 75, and 100% of evapotranspiration demand) with potato
(Solanum tuberosum L. cv. Kennebec) grown at ambient (400) or elevated (800 ppm) CO2 levels.
Experimental photosynthesis and transpiration data from soil-plant-atmosphere research chambers
are used to determine the accuracy of the predictions.