Submitted to: Global Change Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/5/2011
Publication Date: N/A
Interpretive Summary: The Earth is warming globally, which may affect the growth and water use characteristics of wheat – the world’s foremost food and feed crop. Therefore, scientists utilized an ecosystem warming apparatus to induce full-season warming of a spring wheat crop by 1.5 and 3.0°C during the day and night periods, respectively. Measurements of growth and water use were made over a broad range of leaf temperatures throughout the growing season of the crop. Warming of the wheat crop accelerated its growth and created mild drought conditions, which affected water usage. Understanding the effects of global warming on a wheat crop will enable growers and end-users to make more efficient use of water resources in wheat producing regions of the world under conditions of global climate change.
Technical Abstract: Gas exchange and water relations were evaluated under full-season in situ infrared (IR) warming for hard red spring wheat (Triticum aestivum L. cv. Yecora Rojo) grown in an open field in a semiarid desert region of the southwest USA. A temperature free-air controlled enhancement (T-FACE) apparatus utilizing IR heaters maintained canopy air temperature above 3.0 m Heated plots of wheat by 1.3 and 2.7 °C (0.2 and 0.3 °C below the targeted set-points of Reference plots with dummy heaters) during daytime and nighttime, respectively. Control plots had no apparatus. Every 6 weeks during 2007–2009 wheat was sown under the three warming treatments (i.e., Control, Heated, Reference) in three replicates in a 3 × 3 Latin square (LSQ) design on six plantings during 4 months (i.e., January, March, September, December), or in a natural temperature variation treatment (i.e., Control) in three replicates in a randomized complete block (RCB) design on nine plantings during 7 months (i.e., January, February, April, June, July, August, October). Soil temperature (Ts) and volumetric soil-water content ('s) were 1.3 °C warmer and 14% lower in Heated compared with Reference plots, respectively. Other than a 1% shading effect, no artifacts on gas exchange or water relations were associated with the IR warming apparatus. IR warming increased carbon gain characteristic of an increase in metabolic rates to higher temperature that may have been attributed to the well-watered wheat crop and the supplemental irrigation that minimized plant-to-air water vapor pressure differences between IR-warmed and nonwarmed plots. Nevertheless, seasonal oscillations in the IR warming response on carbon gain occurred. IR warming decreased leaf water status and provided thermal protection during freeze events. IR warming is an effective experimental methodology to investigate the impact of global climate change on agronomic cropping and natural ecosystems to a wide range of natural and artificially imposed air temperatures.