title: Historical nitrogen content of bryophyte tissue as an indicator of increased nitrogen deposition in the Cape Metropolitan Area, South Africa.
abstract: Information on changes in precipitation chemistry in the rapidly expanding Cape Metropolitan Area (CMA) of South Africa is scarce. To obtain a long-term record of N deposition we investigated changes in moss foliar N, C:N ratios and nitrogen isotope values that might reflect precipitation chemistry. Tissue from 9 species was obtained from herbarium specimens collected between 1875 and 2000 while field samples were collected in 2001/2002. There is a strong trend of increasing foliar N content in all mosses collected over the past century (1.32-1.69 %N). Differences exist between ectohydric mosses which have higher foliar N than the mixohydric group. C:N ratios declined while foliar delta(15)N values showed no distinct pattern. From relationships between moss tissue N and N deposition rates we estimated an increase of 6-13 kgNha(-1)a(-1) since 1950. Enhanced N deposition rates of this magnitude could lead to biodiversity losses in native ecosystems.
authors.affiliation: Botany Department, University of Cape Town, Rondebosch 7701, South Africa.
authors.forename: D
authors.initials: D
authors.lastname: Wilson
authors.forename: W D
authors.initials: WD
authors.lastname: Stock
authors.forename: T
authors.initials: T
authors.lastname: Hedderson
mesh_terms: D000393:Air Pollutants / Q000032:analysis*; D044002:Bryophyta / Q000737:chemistry*; D004784:Environmental Monitoring / Q000379:methods; D009584:Nitrogen / Q000032:analysis*; D009587:Nitrogen Isotopes / Q000032:analysis; D013019:South Africa; D013997:Time Factors
chemical_list: D000393:Air Pollutants; D009587:Nitrogen Isotopes; D009584:Nitrogen