title: Nitrogen deposition and the biodiversity of boreal forests: implications for the nitrogen critical load.
abstract: The critical load concept is used to establish the deposition levels which ecosystems can tolerate without significant harmful effects. Here we summarize work within the Swedish research program Abatement Strategies for Transboundary Air Pollution (ASTA) assessing the critical load of N for boreal forests. Results from both field experiments in an area with low background N deposition in northern Sweden, and from a large-scale monitoring study, show that important vegetational changes start to take place when adding low N doses and that recovery of the vegetation after ceasing N input is a very slow process. The data presented indicate that changes in key ecosystem components occur even at a lower rate of N input than the present recommended empirical critical load for boreal forest understorey vegetation of 10-15 kg N ha(-1) yr(-1). Based on the data presented, we suggest that the critical load should be lowered to 6 kg N ha(-1) yr(-1).
authors.affiliation: Umeå Plant Science Centre, Department of Forest Genetics and Plant Physiology, Swedish University of Agricultural Sciences, Umeå, Sweden. annika.nordin@genfys.slu.se
authors.forename: Annika
authors.initials: A
authors.lastname: Nordin
authors.forename: Joachim
authors.initials: J
authors.lastname: Strengbom
authors.forename: Johanna
authors.initials: J
authors.lastname: Witzell
authors.forename: Torgny
authors.initials: T
authors.lastname: Näsholm
authors.forename: Lars
authors.initials: L
authors.lastname: Ericson
mesh_terms: D003247:Conservation of Natural Resources; D017753:Ecosystem; D004784:Environmental Monitoring; D009584:Nitrogen / Q000506:poisoning*; D063245:Plant Development; D011157:Population Dynamics; D013548:Sweden; D014197:Trees
chemical_list: D009584:Nitrogen