title: 15N natural abundances and N use by tundra plants.
abstract: Plant species collected from tundra ecosystems located along a north-south transect from central Alaska to the north coast of Alaska showed large and consistent differences in15N natural abundances. Foliar δ15N values varied by about 10% among species within each of two moist tussock tundra sites. Differences in15N contents among species or plant groups were consistent across moist tussock tundra at several other sites and across five other tundra types at a single site. Ericaceous species had the lowest δ15N values, ranging between about -8 to -6‰. Foliar15N contents increased progressively in birch, willows and sedges to maximum δ15N values of about +2‰ in sedges. Soil15N contents in tundra ecosystems at our two most intensively studied sites increased with depth and δ15N values were usually higher for soils than for plants. Isotopic fractionations during soil N transformations and possibly during plant N uptake could lead to observed differences in15N contents among plant species and between plants and soils. Patterns of variation in15N content among species indicate that tundra plants acquire nitrogen in extremely nutrient-poor environments by competitive partitioning of the overall N pool. Differences in plant N sources, rooting depth, mycorrhizal associations, forms of N taken up, and other factors controlling plant N uptake are possible causes of variations in δ15N values of tundra plant species.
authors.affiliation: Marine Biological Laboratory, The Ecosystems Center, 02543, Woods Hole, MA, USA.
authors.forename: K
authors.initials: K
authors.lastname: Nadelhoffer
authors.affiliation: Marine Biological Laboratory, The Ecosystems Center, 02543, Woods Hole, MA, USA.
authors.forename: G
authors.initials: G
authors.lastname: Shaver
authors.affiliation: Marine Biological Laboratory, The Ecosystems Center, 02543, Woods Hole, MA, USA.
authors.forename: B
authors.initials: B
authors.lastname: Fry
authors.affiliation: Marine Biological Laboratory, The Ecosystems Center, 02543, Woods Hole, MA, USA.
authors.forename: A
authors.initials: A
authors.lastname: Giblin
authors.affiliation: Marine Biological Laboratory, The Ecosystems Center, 02543, Woods Hole, MA, USA.
authors.forename: L
authors.initials: L
authors.lastname: Johnson
authors.affiliation: Marine Biological Laboratory, The Ecosystems Center, 02543, Woods Hole, MA, USA.
authors.forename: R
authors.initials: R
authors.lastname: McKane
keywords: 15N abundance; Arctic; N cycle; Nitrate reductase; Tundra