title: Nitrogen mediates above-ground effects of ozone but not below-ground effects in a rhizomatous sedge.
abstract: Ozone and atmospheric nitrogen are co-occurring pollutants with adverse effects on natural grassland vegetation. Plants of the rhizomatous sedge Carex arenaria were exposed to four ozone regimes representing increasing background concentrations (background-peak): 10-30, 35-55, 60-80 and 85-105 ppb ozone at two nitrogen levels: 12 and 100 kg N ha(-1) yr(-1). Ozone increased the number and proportion of senesced leaves, but not overall leaf number. There was a clear nitrogen x ozone interaction with high nitrogen reducing proportional senescence in each treatment and increasing the ozone dose (AOT40) at which enhanced senescence occurred. Ozone reduced total biomass due to significant effects on root biomass. There were no interactive effects on shoot:root ratio. Rhizome tissue N content was increased by both nitrogen and ozone. Results suggest that nitrogen mediates above-ground impacts of ozone but not impacts on below-ground resource translocation. This may lead to complex interactive effects between the two pollutants on natural vegetation.
authors.affiliation: Centre for Ecology and Hydrology (CEH), Environment Centre Wales, Deiniol Road, Bangor, LL57 2UW Wales, UK. lj@ceh.ac.uk
authors.forename: M L M
authors.initials: ML
authors.lastname: Jones
authors.forename: G
authors.initials: G
authors.lastname: Hodges
authors.forename: G
authors.initials: G
authors.lastname: Mills
mesh_terms: D000393:Air Pollutants / Q000378:metabolism* / Q000633:toxicity; D000704:Analysis of Variance; D018533:Biomass; D031255:Carex Plant / Q000187:drug effects* / Q000378:metabolism*; D009584:Nitrogen / Q000032:analysis / Q000378:metabolism* / Q000633:toxicity; D010126:Ozone / Q000378:metabolism* / Q000633:toxicity; D018515:Plant Leaves / Q000187:drug effects / Q000254:growth & development; D018517:Plant Roots / Q000187:drug effects / Q000254:growth & development
chemical_list: D000393:Air Pollutants; D010126:Ozone; D009584:Nitrogen