title: Declining foliar and litter δ¹⁵N diverge from soil, epiphyte and input δ¹⁵N along a 120,000 yr temperate rainforest chronosequence.
abstract: Patterns in the natural abundance of nitrogen (N) isotopes (¹⁵N and ¹⁴N) can help in the understanding of ecosystem processes along environmental gradients, because some processes fractionate against the heavier isotope. We measured δ¹⁵N in many components of the Franz Josef soil chronosequence in New Zealand to see how each component varied along the sequence and within sites, and to see what this variation can tell us about how ecosystem processes such as N losses change with soil age. We analyzed δ¹⁵N in foliage from 18 woody species, abscised leaves from seven woody species, three soil horizons, bryophytes, lichens, bulk deposition, and nodules from the N-fixing tree Coriaria arborea (Coriariaceae). Foliar δ¹⁵N varied significantly across plant species. Foliage and bulk litter became ¹⁵N-depleted as soil age increased. Soil N from organic and mineral horizons was significantly more ¹⁵N-enriched than bulk litter N at each site. Increasing precipitation also decreased foliar and soil δ¹⁵N. Comparing input and whole ecosystem δ¹⁵N revealed limited evidence for net fractionation during N losses. These trends are consistent with some combination of increasing fractionation during plant N uptake, mycorrhizal transfer, within-plant processing, and soil decomposition as soils age.
authors.affiliation: National Center for Ecological Analysis & Synthesis, 735 State St, Suite 300, Santa Barbara, CA, USA.|Department of Ecology and Evolutionary Biology, Princeton University, Princeton, NJ, USA.
authors.forename: Duncan N L
authors.initials: DNL
authors.lastname: Menge
authors.affiliation: National Isotope Center, GNS Science, Lower Hutt, New Zealand.
authors.forename: W
authors.initials: W
authors.lastname: Troy Baisden
authors.affiliation: Landcare Research, PO Box 40, Lincoln, Canterbury 7640, New Zealand.
authors.forename: Sarah J
authors.initials: SJ
authors.lastname: Richardson
authors.affiliation: Landcare Research, PO Box 40, Lincoln, Canterbury 7640, New Zealand.
authors.forename: Duane A
authors.initials: DA
authors.lastname: Peltzer
authors.affiliation: Landcare Research, PO Box 40, Lincoln, Canterbury 7640, New Zealand.|Faculty of Agriculture, Food and Natural Resources, The University of Sydney, 107 Cobbitty Road, Cobbitty, NSW 2570, Australia.
authors.forename: Margaret M
authors.initials: MM
authors.lastname: Barbour
mesh_terms: D044002:Bryophyta / Q000378:metabolism; D017753:Ecosystem; D008011:Lichens / Q000378:metabolism; D019684:Magnoliopsida / Q000378:metabolism*; D009520:New Zealand; D009584:Nitrogen / Q000032:analysis* / Q000378:metabolism; D009587:Nitrogen Isotopes / Q000032:analysis / Q000378:metabolism; D018515:Plant Leaves / Q000378:metabolism; D018517:Plant Roots / Q000378:metabolism*; D012987:Soil / Q000737:chemistry*; D013997:Time Factors; D014197:Trees / Q000737:chemistry
chemical_list: D009587:Nitrogen Isotopes; D012987:Soil; D009584:Nitrogen