Journal Article

Characterization of ozone deposition to a mixed oak–hornbeam forest – flux measurements at five levels above and inside the canopy and their interactions with nitric oxide

Diaz-Pines, Eugenio, Université Paris-Saclay, Marzuoli, Riccardo, Fares, Silvano, Research Centre for Forestry and Wood ; Consiglio per la Ricerca in Agricoltura e l’analisi dell’economia agraria = Council for Agricultural Research and Economics (CREA), Institute of Soil Research ; Universität für Bodenkultur Wien = University of Natural Resources and Life Sciences [Vienne, Autriche] (BOKU), Gerosa, Giacomo, Gasche, Rainer, Ecologie fonctionnelle et écotoxicologie des agroécosystèmes (ECOSYS) ; Institut National de la Recherche Agronomique (INRA)-AgroParisTech, Dipartimento di Matematica e Fisica ; Università cattolica del Sacro Cuore [Piacenza e Cremona] (Unicatt), Finco, Angelo, Loubet, Benjamin, Chiesa, Maria, Centre for Ecology & Hydrology - Bush Estate ; Natural Environment Research Council (NERC), Coyle, Mhairi, Institut für Meteorologie und Klimaforschung - Atmosphärische Umweltforschung (IMK-IFU) ; Karlsruhe Institute of Technology = Karlsruher Institut für Technologie (KIT), Nemitz, Eiko

2018

Overview

A 1-month field campaign of ozone (O3) flux measurements along a five-level vertical profile above, inside and below the canopy was run in a mature broadleaf forest of the Po Valley, northern Italy. The study aimed to characterize O3 flux dynamics and their interactions with nitrogen oxides (NOx) fluxes from the forest soil and the atmosphere above the canopy. Ozone fluxes measured at the levels above the canopy were in good agreement, thus confirming the validity of the constant flux hypothesis, while below-canopy O3 fluxes were lower than above. However, at the upper canopy edge O3 fluxes were surprisingly higher than above during the morning hours. This was attributed to a chemical O3 sink due to a reaction with the nitric oxide (NO) emitted from soil and deposited from the atmosphere, thus converging at the top of the canopy. Moreover, this mechanism was favored by the morning coupling between the forest and the atmosphere, while in the afternoon the fluxes at the upper canopy edge became similar to those of the levels above as a consequence of the in-canopy stratification. Nearly 80 % of the O3 deposited to the forest ecosystem was removed by the canopy by stomatal deposition, dry deposition on physical surfaces and by ambient chemistry reactions (33.3 % by the upper canopy layer and 46.3 % by the lower canopy layer). Only a minor part of O3 was removed by the understorey vegetation and the soil surface (2 %), while the remaining 18.2 % was consumed by chemical reaction with NO emitted from soil. The collected data could be used to improve the O3 risk assessment for forests and to test the predicting capability of O3 deposition models. Moreover, these data could help multilayer canopy models to separate the influence of ambient chemistry vs. O3 dry deposition on the observed fluxes.

• Publisher: European Geosciences Union,CCSD,Copernicus GmbH,Copernicus Publications
• Subject: Analysis / Atmosphere / Atmospheric chemistry / Atmospheric deposition / Atmospheric models / Canopies / Canopy / Chemical reactions / Density stratification / Deposition / Dry deposition / Dynamics / Emission measurements / Environmental aspects / Fluctuations / Fluxes / Forest ecosystems / Forest microclimatology / Forest soils / Forests / Herbivores / Interactions / Life Sciences / Multilayers / Nitric oxide / Nitrogen compounds / Nitrogen oxides / Organic chemistry / Oxides / Ozone / Ozone deposition / Photochemicals / Risk assessment / Soil / Soil surfaces / Stomata / Stratification / Vertical profiles
• ISBN: 0004535789000