title: Forest floor vegetation response to nitrogen deposition in Europe.
abstract: Chronic nitrogen (N) deposition is a threat to biodiversity that results from the eutrophication of ecosystems. We studied long-term monitoring data from 28 forest sites with a total of 1,335 permanent forest floor vegetation plots from northern Fennoscandia to southern Italy to analyse temporal trends in vascular plant species cover and diversity. We found that the cover of plant species which prefer nutrient-poor soils (oligotrophic species) decreased the more the measured N deposition exceeded the empirical critical load (CL) for eutrophication effects (P = 0.002). Although species preferring nutrient-rich sites (eutrophic species) did not experience a significantly increase in cover (P = 0.440), in comparison to oligotrophic species they had a marginally higher proportion among new occurring species (P = 0.091). The observed gradual replacement of oligotrophic species by eutrophic species as a response to N deposition seems to be a general pattern, as it was consistent on the European scale. Contrary to species cover changes, neither the decrease in species richness nor of homogeneity correlated with nitrogen CL exceedance (ExCLemp N). We assume that the lack of diversity changes resulted from the restricted time period of our observations. Although existing habitat-specific empirical CL still hold some uncertainty, we exemplify that they are useful indicators for the sensitivity of forest floor vegetation to N deposition.
authors.affiliation: Department for Ecosystem Research and Monitoring, Environment Agency Austria, Spittelauer Lände 5, A-1090, Vienna, Austria.
authors.forename: Thomas
authors.initials: T
authors.lastname: Dirnböck
authors.forename: Ulf
authors.initials: U
authors.lastname: Grandin
authors.forename: Markus
authors.initials: M
authors.lastname: Bernhardt-Römermann
authors.forename: Burkhardt
authors.initials: B
authors.lastname: Beudert
authors.forename: Roberto
authors.initials: R
authors.lastname: Canullo
authors.forename: Martin
authors.initials: M
authors.lastname: Forsius
authors.forename: Maria-Theresia
authors.initials: MT
authors.lastname: Grabner
authors.forename: Maria
authors.initials: M
authors.lastname: Holmberg
authors.forename: Sirpa
authors.initials: S
authors.lastname: Kleemola
authors.forename: Lars
authors.initials: L
authors.lastname: Lundin
authors.forename: Michael
authors.initials: M
authors.lastname: Mirtl
authors.forename: Markus
authors.initials: M
authors.lastname: Neumann
authors.forename: Enrico
authors.initials: E
authors.lastname: Pompei
authors.forename: Maija
authors.initials: M
authors.lastname: Salemaa
authors.forename: Franz
authors.initials: F
authors.lastname: Starlinger
authors.forename: Tomasz
authors.initials: T
authors.lastname: Staszewski
authors.forename: Aldona Katarzyna
authors.initials: AK
authors.lastname: Uziębło
mesh_terms: D044822:Biodiversity; D017753:Ecosystem; D005060:Europe; D005068:Eutrophication; D009584:Nitrogen / Q000378:metabolism*; D018521:Plant Physiological Phenomena
chemical_list: D009584:Nitrogen
keywords: air pollution; critical load; eutrophication; long-term ecological research; monitoring; plant species diversity