Future carbon dioxide concentration decreases canopy evapotranspiration and soil water depletion by field-grown maize

• Published in: Global change biology Vol. 19; no. 5; pp. 1572 - 1584
• Main Authors: Hussain, Mir Zaman, VanLoocke, Andy, Siebers, Matthew H., Ruiz-Vera, Ursula M., Cody Markelz, R. J., Leakey, Andrew D. B., Ort, Donald R., Bernacchi, Carl J.
• Format: Journal Article
• Language: English
• Published: Oxford Blackwell Publishing Ltd 01.05.2013; Wiley-Blackwell
• Subjects: Animal and plant ecology; Animal, plant and microbial ecology; Biological and medical sciences; canopy temperature; Carbon dioxide; Carbon Dioxide - metabolism; Circadian Rhythm; Climate Change; Corn; elevated [CO2]; Energy Metabolism; Evapotranspiration; Fundamental and applied biological sciences. Psychology; General aspects; Hydrologic cycle; Illinois; maize; Moisture content; Photosynthesis; Plant Leaves - physiology; Plant Transpiration; Seasons; sensible heat; Soil - chemistry; soil moisture; Soils; Time Factors; Water - metabolism; Zea mays; Zea mays - physiology; USA, Illinois; sensible heat; Monocotyledones; Temperature; Zea mays; Soil moisture; Water deficit; Carbon dioxide; Environmental factor; Increase; Concentration; maize; Concentration measurement; Medium enrichment; Soils; Heat; canopy temperature; elevated [CO; Gramineae; Angiospermae; Evapotranspiration; Spermatophyta; ]; Canopy(vegetation)
• ISSN: 1354-1013; 1365-2486
• DOI: 10.1111/gcb.12155

Maize, in rotation with soybean, forms the largest continuous ecosystem in temperate North America, therefore changes to the biosphere‐atmosphere exchange of water vapor and energy of these crops are likely to have an impact on the Midwestern US climate and hydrological cycle. As a C4 crop, maize photosynthesis is already CO2‐saturated at current CO2 concentrations ([CO2]) and the primary response of maize to elevated [CO2] is decreased stomatal conductance (gs). If maize photosynthesis is not stimulated in elevated [CO2], then reduced gs is not offset by greater canopy leaf area, which could potentially result in a greater ET reduction relative to that previously reported in soybean, a C3 species. The objective of this study is to quantify the impact of elevated [CO2] on canopy energy and water fluxes of maize (Zea mays). Maize was grown under ambient and elevated [CO2] (550 μmol mol−1 during 2004 and 2006 and 585 μmol mol−1 during 2010) using Free Air Concentration Enrichment (FACE) technology at the SoyFACE facility in Urbana, Illinois. Maize ET was determined using a residual energy balance approach based on measurements of sensible (H) and soil heat fluxes, and net radiation. Relative to control, elevated [CO2] decreased maize ET (7–11%; P < 0.01) along with lesser soil moisture depletion, while H increased (25–30 W m−2; P < 0.01) along with higher canopy temperature (0.5–0.6 °C). This reduction in maize ET in elevated [CO2] is approximately half that previously reported for soybean. A partitioning analysis showed that transpiration contributed less to total ET for maize compared to soybean, indicating a smaller role of stomata in dictating the ET response to elevated [CO2]. Nonetheless, both maize and soybean had significantly decreased ET and increased H, highlighting the critical role of elevated [CO2] in altering future hydrology and climate of the region that is extensively cropped with these species.