Submitted to: The Earth's Changing Land Global Change and Terrestrial Ecosystems and Land
Publication Type: Abstract Only
Publication Acceptance Date: May 26, 1998
Publication Date: N/A
Free Air Carbon-dioxide Enrichment (FACE) experiments were conducted in 1995-96 at Maricopa, AZ, to investigate the dynamics of CO2-nitrogen interactions in spring wheat (Tricticum aestivum L., cv. Yecora Rojo). We use these data to further test mC-Wheat, validated with previous CO2- water FACE experiments in 1992-93 and 1993-94, using observed data on plant phenology, plant dry matter production, and its subsequent partitioning to leaf stem root and grain organs. We develop anew subroutine that includes effects of water stress on canopy temperature, following observations in previous FACE experiments that suggest a shortening of the time to grain maturity under conditions that favour stomatal closure. Dasets from the 1992-93 and 1994-95 FACE experiments are used to develop the new subroutine, which is then evaluated using the 1995-96 treatments. Six simulations are performed for the 1995-96 FACE experiments, representing combinations of two fertilization treatments (low N and high N) and three atmospheric CO2 treatments (control with no blower, 350 ppm control with blower, 350 ppm and FACE, 550 ppm). The model well simulates plant phenology in all experiments, with an overall correlation coefficient of R^2=0.98 between simulated and observed dates of anthesis and physiiological maturity. Model- simulated effects of CO2 concentration and fertilizer application on total above-ground, leaf, stem, root and grain dry matter production are in agreement with observations but model performance is not as good as previous CO2-water simulations.