title: Nitrogen and phosphorus co-limitation and grazing moderate nitrogen impacts on plant growth and nutrient cycling in sand dune grassland.
abstract: Atmospheric nitrogen (N) deposition alters plant biodiversity and ecosystem function in grasslands worldwide. This study examines the impact of 6 years of nutrient addition and grazing management on a sand dune grassland. Results indicate that co-limitation of N and phosphorus (P) moderates the impact of realistic rates of N addition (7.5, 15 kg N ha(1) year(-1)). Combined NP addition (15 kg N + 10 kg P ha(-1) year(-1)) was the only nutrient treatment to differ significantly from the control, with greater above-ground biomass (mainly moss), and enhanced N and P mineralisation rates. Grazing management altered plant functional group composition, reduced above-ground biomass and meso-faunal feeding rates, and decoupled N and P mineralisation. There were no synergistic effects of grazing and N treatment. Although NP co-limitation apparently prevents adverse impacts of N deposition above the critical load, excess N is likely to be stored in moss biomass and soil, with unknown future consequences.
  This study shows that at realistic levels of N addition, NP co-limitation in a dune grassland appears to prevent adverse impacts of N on plant growth and nutrient cycling.
authors.affiliation: School of Ocean Sciences, Bangor University, Anglesey LL59 5AB, UK; Centre for Ecology and Hydrology, Environment Centre Wales, Bangor LL57 2UW, UK. Electronic address: hilary.ford@bangor.ac.uk.
authors.forename: Hilary
authors.initials: H
authors.lastname: Ford
authors.affiliation: Centre for Ecology and Hydrology, Environment Centre Wales, Bangor LL57 2UW, UK.
authors.forename: Aled
authors.initials: A
authors.lastname: Roberts
authors.affiliation: Centre for Ecology and Hydrology, Environment Centre Wales, Bangor LL57 2UW, UK. Electronic address: lj@ceh.ac.uk.
authors.forename: Laurence
authors.initials: L
authors.lastname: Jones
mesh_terms: D055669:Ecological and Environmental Phenomena; D004784:Environmental Monitoring; D065948:Grassland; D060434:Herbivory; D009584:Nitrogen / Q000032:analysis*; D010758:Phosphorus / Q000032:analysis*; D063245:Plant Development
chemical_list: D010758:Phosphorus; D009584:Nitrogen
keywords: Bait lamina; Biodiversity; Critical load; Mineralisation; Nitrogen deposition