Abstract
Tropospheric O3 can impact soil systems mediated by changing root biomass and exudates. This study investigated how elevated O3 alters soil CO2 and N2O emissions from a winter wheat field. Winter wheat (Triticum aestivum L.) were fumigated using elevated O3 concentration (EO3) and using ambient air within open-top chambers during 2015 and 2016. Soil CO2 and N2O emissions were measured using a static closed-chamber technique. Rhizosphere soils were collected to determine dissolved organic carbon (DOC) content, ammonium-nitrogen (NH4+-N) and nitrate-nitrogen (NO3−-N) concentrations, microbial biomass carbon (MBC) and nitrogen (MBN), and activities of nitrate reductase (NR), nitrite reductase (NiR) and hydroxylamine reductase (HR). Moreover, volumetric soil water content (θv) was monitored and plant dry biomass was quantified. The EO3 treatment exhibited decreased CO2 and increased N2O emissions from winter wheat soil. Soil NH4+-N, NO3−-N, NR and NiR increased under EO3, whereas DOC, MBC, MBN and HR decreased. Soil θv was higher under EO3 before irrigation, due to reduced transpiration. Elevated O3 decreased soil CO2 flux potentially due to reduced root biomass and associated carbon input. It increased N2O fluxes apparently through enhanced denitrification due to greater substrate availability and soil θv, despite the inhibition of nitrification-related routes.
Published Version
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