Rising ozone concentrations decrease soybean evapotranspiration and water use efficiency whilst increasing canopy temperature

Abstract

Here, we investigated the effects of increasing concentrations of ozone ([O 3]) on soybean canopy-scale fluxes of heat and water vapor, as well as water use efficiency (WUE), at the Soybean Free Air Concentration Enrichment (SoyFACE) facility. • Micrometeorological measurements were made to determine the net radiation (R n), sensible heat flux (H), soil heat flux (G 0) and latent heat flux (λET) of a commercial soybean (Glycine max) cultivar (Pioneer 93B15), exposed to a gradient of eight daytime average ozone concentrations ranging from approximately current (c. 40ppb) to three times current (c. 120ppb) levels. • As [O 3] increased, soybean canopy fluxes of λET decreased and H increased, whereas R n and G 0 were not altered significantly. Exposure to increased [O 3] also resulted in warmer canopies, especially during the day. The lower λET decreased season total evapotranspiration (ET) by c. 26%. The [O 3]-induced relative decline in ET was half that of the relative decline in seed yield, driving a 50% reduction in seasonal WUE. • These results suggest that rising [O 3] will alter the canopy energy fluxes that drive regional climate and hydrology, and have a negative impact on productivity and WUE, key ecosystem services. © 2012 New Phytologist Trust.