title: Combining sap flow and eddy covariance approaches to derive stomatal and non-stomatal O3 fluxes in a forest stand.
abstract: Stomatal O3 fluxes to a mixed beech/spruce stand (Fagus sylvatica/Picea abies) in Central Europe were determined using two different approaches. The sap flow technique yielded the tree-level transpiration, whereas the eddy covariance method provided the stand-level evapotranspiration. Both data were then converted into stomatal ozone fluxes, exemplifying this novel concept for July 2007. Sap flow-based stomatal O3 flux was 33% of the total O3 flux, whereas derivation from evapotranspiration rates in combination with the Penman-Monteith algorithm amounted to 47%. In addition to this proportional difference, the sap flow-based assessment yielded lower levels of stomatal O3 flux and reflected stomatal regulation rather than O3 exposure, paralleling the daily courses of canopy conductance for water vapor and eddy covariance-based total stand-level O3 flux. The demonstrated combination of sap flow and eddy covariance approaches supports the development of O3 risk assessment in forests from O3 exposure towards flux-based concepts.
authors.affiliation: Ecophysiology of Plants, Technische Universität München, Am Hochanger 13, D-85354 Freising-Weihenstephan, Germany.
authors.forename: A J
authors.initials: AJ
authors.lastname: Nunn
authors.forename: S
authors.initials: S
authors.lastname: Cieslik
authors.forename: U
authors.initials: U
authors.lastname: Metzger
authors.forename: G
authors.initials: G
authors.lastname: Wieser
authors.forename: R
authors.initials: R
authors.lastname: Matyssek
mesh_terms: D004781:Environmental Exposure / Q000032:analysis; D004784:Environmental Monitoring / Q000379:methods*; D029964:Fagus / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism*; D005858:Germany; D010126:Ozone / Q000032:analysis / Q000493:pharmacokinetics* / Q000494:pharmacology; D028222:Picea / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism*; D053147:Plant Exudates / Q000378:metabolism*; D054046:Plant Stomata / Q000187:drug effects / Q000378:metabolism* / Q000502:physiology; D018526:Plant Transpiration / Q000187:drug effects / Q000502:physiology*; D018570:Risk Assessment; D013045:Species Specificity; D014919:Wind; D052584:Xylem / Q000187:drug effects / Q000378:metabolism / Q000502:physiology
chemical_list: D053147:Plant Exudates; D010126:Ozone