Articles | Volume 14, issue 7
Research article
05 Apr 2017
Research article |  | 05 Apr 2017

No impact of tropospheric ozone on the gross primary productivity of a Belgian pine forest

Lore T. Verryckt, Maarten Op de Beeck, Johan Neirynck, Bert Gielen, Marilyn Roland, and Ivan A. Janssens

Abstract. High stomatal ozone (O3) uptake has been shown to negatively affect crop yields and the growth of tree seedlings. However, little is known about the effect of O3 on the carbon uptake by mature forest trees. This study investigated the effect of high O3 events on gross primary productivity (GPP) for a Scots pine stand near Antwerp, Belgium over the period 1998–2013. Stomatal O3 fluxes were modelled using in situ O3 mixing ratio measurements and a multiplicative stomatal model, which was parameterised and validated for this Scots pine stand. Ozone-induced GPP reduction is most likely to occur during or shortly after days with high stomatal O3 uptake. Therefore, a GPP model within an artificial neural network was parameterised for days with low stomatal O3 uptake rates and used to simulate GPP during periods of high stomatal O3 uptake. Possible negative effects of high stomatal O3 uptake on GPP would then result in an overestimation of GPP by the model during or after high stomatal O3 uptake events. The O3 effects on GPP were linked to AOT40 and POD1. Although the critical levels for both indices were exceeded in every single year, no significant negative effects of O3 on GPP were found, and no correlations between GPP residuals and AOT40 and POD1 were found. Overall, we conclude that no O3 effects were detected on the carbon uptake by this Scots pine stand.

Short summary
Ozone (O3) is an air pollutant known to negatively affect vegetation. Typically, high O3 concentrations reduce growth. This study investigated the effect of O3 uptake on the total amount of carbon assimilated by vegetation for a Scots pine stand in Flanders over the period 1998–2013. Although the critical levels for AOT40 and POD1, two indices currently used to estimate O3 damage, were exceeded every year, no O3 effects on daily and growing season GPP were found.
Final-revised paper