title: Contributing factors in foliar uptake of dissolved inorganic nitrogen at leaf level.
abstract: We investigated the influence of leaf traits, rainwater chemistry, and pedospheric nitrogen (N) fertilisation on the aqueous uptake of inorganic N by physiologically active tree leaves. Leaves of juvenile silver birch and European beech trees, supplied with NH₄NO₃ to the soil at rates from 0 to 200 kg N ha(-1)y(-1), were individually exposed to 100 μl of artificial rainwater containing (15)NH₄(+) or (15)NO₃(-) at two concentration levels for one hour. In the next vegetative period, the experiment was repeated with NH₄(+) at the highest concentration only. The N form and the N concentration in the applied rainwater and, to a lesser extent, the pedospheric N treatment and the leaf traits affected the aqueous foliar N uptake. The foliar uptake of NH₄(+) by birch increased when leaves were more wettable. High leaf N concentration and leaf mass per area enhanced the foliar N uptake, and NO₃(-) uptake in particular, by birch. Variation in the foliar N uptake by the beech trees could not be explained by the leaf traits considered. In the first experiment, N fertilisation stimulated the foliar N uptake in both species, which was on average 1.42-1.78 times higher at the highest soil N dose than at the zero dose. However, data variability was high and the effect was not appreciable in the second experiment. Our data suggest that next to rainwater chemistry (N form and concentration) also forest N status could play a role in the partitioning of N entering the ecosystem through the soil and the canopy. Models of canopy uptake of aqueous N at the leaf level should take account of leaf traits such as wettability and N concentration.
authors.affiliation: Laboratory of Environmental and Urban Ecology, Research Group ENdEMIC, Dept. Bioscience Engineering, University of Antwerp, Groenenborgerlaan 171, B-2020 Antwerp, Belgium; Forest & Nature Lab (ForNaLab), Dept. Forest and Water Management, Ghent University, Geraardsbergsesteenweg 267, B-9090 Gontrode-Melle, Belgium. Electronic address: karen.wuyts@uantwerpen.be.
authors.forename: Karen
authors.initials: K
authors.lastname: Wuyts
authors.affiliation: Belgian Interregional Environment Agency (IRCEL-CELINE), Kunstlaan 10-11, B-1210 Brussels, Belgium. Electronic address: adriaenssens@irceline.be.
authors.forename: Sandy
authors.initials: S
authors.lastname: Adriaenssens
authors.affiliation: Flemish Environment Agency (VMM), Kronenburgstraat 45, B-2000 Antwerp, Belgium. Electronic address: jeroen_staelens@yahoo.com.
authors.forename: Jeroen
authors.initials: J
authors.lastname: Staelens
authors.affiliation: Laboratory of Environmental and Urban Ecology, Research Group ENdEMIC, Dept. Bioscience Engineering, University of Antwerp, Groenenborgerlaan 171, B-2020 Antwerp, Belgium. Electronic address: tatiana.wuytack@uantwerpen.be.
authors.forename: Tatiana
authors.initials: T
authors.lastname: Wuytack
authors.affiliation: Laboratory of Environmental and Urban Ecology, Research Group ENdEMIC, Dept. Bioscience Engineering, University of Antwerp, Groenenborgerlaan 171, B-2020 Antwerp, Belgium. Electronic address: shari.vanwittenberghe@uantwerpen.be.
authors.forename: Shari
authors.initials: S
authors.lastname: Van Wittenberghe
authors.affiliation: Isotope Bioscience Laboratory (ISOFYS), Dept. Applied Analytical and Physical Chemistry, Ghent University, Coupure Links 653, B-9000 Ghent, Belgium. Electronic address: pascal.boeckx@ugent.be.
authors.forename: Pascal
authors.initials: P
authors.lastname: Boeckx
authors.affiliation: Laboratory of Environmental and Urban Ecology, Research Group ENdEMIC, Dept. Bioscience Engineering, University of Antwerp, Groenenborgerlaan 171, B-2020 Antwerp, Belgium. Electronic address: roeland.samson@uantwerpen.be.
authors.forename: Roeland
authors.initials: R
authors.lastname: Samson
authors.affiliation: Forest & Nature Lab (ForNaLab), Dept. Forest and Water Management, Ghent University, Geraardsbergsesteenweg 267, B-9090 Gontrode-Melle, Belgium. Electronic address: kris.verheyen@ugent.be.
authors.forename: Kris
authors.initials: K
authors.lastname: Verheyen
mesh_terms: D017753:Ecosystem; D007287:Inorganic Chemicals / Q000032:analysis*; D009584:Nitrogen / Q000032:analysis*; D010788:Photosynthesis / Q000502:physiology; D018515:Plant Leaves / Q000737:chemistry* / Q000502:physiology; D014197:Trees / Q000502:physiology*
chemical_list: D007287:Inorganic Chemicals; D009584:Nitrogen
keywords: Drop contact angle; Foliar uptake; Inorganic nitrogen; Leaf mass per area; Leaf nitrogen concentration; Pedospheric fertilisation