title: Increasing trends of dissolved organic nitrogen (DON) in temperate forests under recovery from acidification in Flanders, Belgium.
abstract: We evaluated trends (2005-2013) and patterns of dissolved organic nitrogen (DON) and its ratio with dissolved organic carbon (DOC), DOC:DON in atmospheric deposition and soil solution of five Level II plots of the International Co-operative Programme on Assessment and Monitoring of Air Pollution Effects on Forests (ICP Forests) in Flanders, Northern Belgium. The primary aim was to confirm positive postulated trends in DON levels and DOC:DON under on-going recovery from acidification. The DON concentrations (0.95-1.41 mg L(-1)) and fluxes (5.6-8.3 kg ha(-1)y(-1)) in throughfall were about twice as high compared to precipitation in the open field (0.40-0.48 mg L(-1), 3.0-3.9 kg ha(-1)y(-1)). Annual soil profile leaching losses of DON varied between 1.2 and 3.7 kg ha(-1)y(-1). The highest soil DON concentrations and fluxes were observed beneath the O horizon (1.84-2.36 mg L(-1), 10.1-12.3 kg ha(-1)y(-1)). Soil solution concentrations and fluxes of DON showed significant increasing trends. Temporarily soil solution DOC:DON rose following an exceptionally long spring drought in 2007, suggesting an effect of drying and rewetting on DOM composition. Further research is needed to test the dependence of DON and DOC:DON on factors such as latitude, forest cover, length of the growing season, hydrology and topography. Nonetheless, even with considerable variation in soil type, level of base saturation, and soil texture in the five included ICP Forests Level II plots, all data revealed a proportionally larger positive response of DON flux than DOC to recovery from acidification.
authors.affiliation: INBO, Research Institute for Nature and Forest, Kliniekstraat 25, 1070 Brussels, Belgium; University of Ghent, Department of Soil Management, Coupure Links 653, 9000 Ghent, Belgium. Electronic address: arne.verstraeten@inbo.be.
authors.forename: Arne
authors.initials: A
authors.lastname: Verstraeten
authors.affiliation: INBO, Research Institute for Nature and Forest, Kliniekstraat 25, 1070 Brussels, Belgium. Electronic address: pieter.verschelde@inbo.be.
authors.forename: Pieter
authors.initials: P
authors.lastname: Verschelde
authors.affiliation: INBO, Research Institute for Nature and Forest, Kliniekstraat 25, 1070 Brussels, Belgium. Electronic address: bruno.devos@inbo.be.
authors.forename: Bruno
authors.initials: B
authors.lastname: De Vos
authors.affiliation: INBO, Research Institute for Nature and Forest, Kliniekstraat 25, 1070 Brussels, Belgium. Electronic address: johan.neirynck@inbo.be.
authors.forename: Johan
authors.initials: J
authors.lastname: Neirynck
authors.affiliation: INBO, Research Institute for Nature and Forest, Kliniekstraat 25, 1070 Brussels, Belgium. Electronic address: nathalie.cools@inbo.be.
authors.forename: Nathalie
authors.initials: N
authors.lastname: Cools
authors.affiliation: INBO, Research Institute for Nature and Forest, Kliniekstraat 25, 1070 Brussels, Belgium. Electronic address: peter.roskams@inbo.be.
authors.forename: Peter
authors.initials: P
authors.lastname: Roskams
authors.affiliation: INBO, Research Institute for Nature and Forest, Kliniekstraat 25, 1070 Brussels, Belgium. Electronic address: maarten.hens1@telenet.be.
authors.forename: Maarten
authors.initials: M
authors.lastname: Hens
authors.affiliation: INBO, Research Institute for Nature and Forest, Kliniekstraat 25, 1070 Brussels, Belgium. Electronic address: gerald.louette@inbo.be.
authors.forename: Gerald
authors.initials: G
authors.lastname: Louette
authors.affiliation: University of Ghent, Department of Soil Management, Coupure Links 653, 9000 Ghent, Belgium. Electronic address: steven.sleutel@ugent.be.
authors.forename: Steven
authors.initials: S
authors.lastname: Sleutel
authors.affiliation: University of Ghent, Department of Soil Management, Coupure Links 653, 9000 Ghent, Belgium. Electronic address: stefaan.deneve@ugent.be.
authors.forename: Stefaan
authors.initials: S
authors.lastname: De Neve
mesh_terms: D001530:Belgium; D004784:Environmental Monitoring; D065928:Forests; D009584:Nitrogen / Q000032:analysis*; D012987:Soil / Q000737:chemistry*
chemical_list: D012987:Soil; D009584:Nitrogen
keywords: Acidification; Dissolved organic matter; Dissolved organic nitrogen; ICP Forests; Temperate forests; Temporal trends