title: Plant nitrogen concentration and isotopic composition in residential lawns across seven US cities.
abstract: Human drivers are often proposed to be stronger than biophysical drivers in influencing ecosystem structure and function in highly urbanized areas. In residential land cover, private yards are influenced by individual homeowner preferences and actions while also experiencing large-scale human and biophysical drivers. We studied plant nitrogen (%N) and N stable isotopic composition (δ(15)N) in residential yards and paired native ecosystems in seven cities across the US that span major ecological biomes and climatic regions: Baltimore, Boston, Los Angeles, Miami, Minneapolis-St. Paul, Phoenix, and Salt Lake City. We found that residential lawns in three cities had enriched plant δ(15)N (P < 0.03) and in six cities higher plant N (%) relative to the associated native ecosystems (P < 0.05). Plant δ(15)N was progressively depleted across a gradient of urban density classes in Baltimore and Boston (P < 0.05). Lawn fertilization was associated with depleted plant δ(15)N in Boston and Los Angeles (P < 0.05), and organic fertilizer additions were associated with enriched plant δ(15)N in Los Angeles and Salt Lake City (P < 0.04). Plant δ(15)N was significantly enriched as a function of housing age in Baltimore (r (2) = 0.27, P < 0.02), Boston (r (2) = 0.27, P < 0.01), and Los Angeles (r (2) = 0.34, P < 0.01). These patterns in plant δ(15)N and plant N (%) across these cities suggests that N sources to lawns, as well as greater rates of N cycling combined with subsequent N losses, may be important drivers of plant N dynamics in lawn ecosystems at the national scale.
authors: Department of Plant and Soil Sciences, University of Delaware, Newark, DE, USA. ttram@udel.edu.
authors: T L E
authors: TL
authors: Trammell
authors: Department of Biology, University of Utah, Salt Lake City, UT, USA.
authors: D E
authors: DE
authors: Pataki
authors: Department of Ecology, Evolution, and Behavior, University of Minnesota, St. Paul, MN, USA.
authors: J
authors: J
authors: Cavender-Bares
authors: Cary Institute of Ecosystem Studies, Millbrook, NY, USA.
authors: P M
authors: PM
authors: Groffman
authors: School of Life Sciences, Arizona State University, Tempe, AZ, USA.
authors: S J
authors: SJ
authors: Hall
authors: Nicholas School of the Environment, Duke University, Durham, NC, USA.
authors: J B
authors: JB
authors: Heffernan
authors: Department of Ecology, Evolution, and Behavior, University of Minnesota, St. Paul, MN, USA.
authors: S E
authors: SE
authors: Hobbie
authors: Cary Institute of Ecosystem Studies, Millbrook, NY, USA.|Environmental Science and Management, Portland State University, Portland, OR, USA.
authors: J L
authors: JL
authors: Morse
authors: The Ecosystems Center, Marine Biological Laboratory, Woods Hole, MA, USA.
authors: C
authors: C
authors: Neill
authors: Department of Forest Resources and Department of Fisheries, Wildlife, and Conservation Biology, University of Minnesota, St. Paul, MN, USA.
authors: K C
authors: KC
authors: Nelson
mesh_terms: D002947:Cities; D017753:Ecosystem; D005308:Fertilizers / Q000032:analysis*; D009584:Nitrogen / Q000378:metabolism*; D009587:Nitrogen Isotopes / Q000378:metabolism; D010944:Plants / Q000378:metabolism*; D013997:Time Factors; D014481:United States
chemical_list: D005308:Fertilizers; D009587:Nitrogen Isotopes; D009584:Nitrogen
keywords: Ecological convergence; Natural abundance nitrogen stable isotopes; Nitrogen cycling; Urban ecology