Effects of Full-Season Temperature Free-Air-Controlled Enhancement (T-FACE) Ecosystem Warming on Development of Spring Wheat.

In agricultural systems, a dominant effect of global warming is likely to be manifested through accelerated development. While our qualitative understanding of the effects of temperature on development is extensive, our ability to quantitatively predict how temperature affects processes such as leaf appearance and reproductive development still requires refinement. Controlled environment chambers have been extensively used to study effects of temperature on development, but such systems introduce numerous biases relative to field situations. Infrared heaters can permit warming treatments to be applied to field plots. This paper compares effects of temperature on leaf appearance and phenology in spring wheat (Triticum aestivum L. cv. Yecora Rojo) using infrared heaters and planting dates to provide different temperature regimes at Maricopa, AZ. The primary objective was to determine whether the T-FACE system resulted in temperature responses that were quantitatively similar to those from natural variation obtained through planting dates. The T-FACE apparatus provided full-season warming of the canopy by 3 and 1.5 ºC during the diurnal and nocturnal periods, respectively. Heated treatments with controls were grown in January, March, and September of 2007 and 2008. Additional planting dates were attempted approximately every seven weeks. Plots were evaluated for leaf appearance and growth stages including emergence, heading, anthesis, and physiological maturity. Leaf appearance rates were estimated assuming a linear increase in leaf number with growing degree days. Timing of growth stages was simulated using the CSM-Cropsim-CERES-Wheat model, which includes effects of vernalization and photoperiod, and field observations were then compared to simulations using regression. Results from T-FACE and planting dates were similar, indicating that the T-FACE system provides temperature regimes comparable to those obtained from planting date studies and confirming the utility of the system for studying effects of global warming at field scales.