The impact of drought on total ozone flux in a mountain Norway spruce forest

Abstract

In order to understand the impact of summer drought on dry deposition of tropospheric ozone (O3), we compared severe and mild drought periods of summer 2018 in a mountain Norway spruce forest at Bílý Kří', Beskydy Mts. An eddy covariance technique was applied to measure diurnal courses of the ecosystem O and CO fluxes. Low O3deposition was recorded in the morning and evening, while the highest CO2and O3fluxes were recorded during the central hours of the day. Total O3deposition during severe drought (soil humidity 13%) was significantly higher than the deposition during the mild drought period (soil humidity 19%). Our data indicate that high vapour pressure deficit and low soil humidity during severe drought led to the stomatal closure, while non-stomatal O3deposition, associated with chemical reactions of O3with NO and volatile organic compounds, are responsible for higher total O3deposition during the severe drought period. Therefore, we assume that under severe drought stomatal 3 uptake decreases but non-stomatal depositions to forest ecosystems substantially increase.