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Title

Sources of increased N uptake in forest trees growing under elevated CO2: results of a large-scale N-15 study

Publication Year

2011

Author(s)
  • Hofmockel, Kirsten S.
  • Gallet-Budynek, Anne
  • McCarthy, Heather R.
  • Currie, William S.
  • Jackson, Robert B.
  • Finzi, Adrien C.
Source
GLOBAL CHANGE BIOLOGY Volume: 17 Issue: 11 Pages: 3338-3350 Published: 2011
ISSN
1354-1013
Abstract

Nitrogen availability in terrestrial ecosystems strongly influences plant productivity and nutrient cycling in response to increasing atmospheric carbon dioxide (CO2). Elevated CO2 has consistently stimulated forest productivity at the Duke Forest free-air CO2 enrichment experiment throughout the decade-long experiment. It remains unclear how the N cycle has changed with elevated CO2 to support this increased productivity. Using natural-abundance measures of N isotopes together with an ecosystem-scale N-15 tracer experiment, we quantified the cycling of N-15 in plant and soil pools under ambient and elevated CO2 over three growing seasons to determine how elevated CO2 changed N cycling between plants, soil, and microorganisms. After measuring natural-abundance N-15 differences in ambient and CO2-fumigated plots, we applied inorganic N-15 tracers and quantified the redistribution of N-15 for three subsequent growing seasons. The natural abundance of leaf litter was enriched under elevated compared to ambient CO2, consistent with deeper rooting and enhanced N mineralization. After tracer application, N-15 was initially retained in the organic and mineral soil horizons. Recovery of N-15 in plant biomass was 3.5 +/- 0.5% in the canopy, 1.7 +/- 0.2% in roots and 1.7 +/- 0.2% in branches. After two growing seasons, N-15 recoveries in biomass and soil pools were not significantly different between CO2 treatments, despite greater total N uptake under elevated CO2. After the third growing season, N-15 recovery in trees was significantly higher in elevated compared to ambient CO2. Natural-abundance N-15 and tracer results, taken together, suggest that trees growing under elevated CO2 acquired additional soil N resources to support increased plant growth. Our study provides an integrated understanding of elevated CO2 effects on N cycling in the Duke Forest and provides a basis for inferring how C and N cycling in this forest may respond to elevated CO2 beyond the decadal time scale.

Author Keyword(s)
  • N-15
  • atmospheric CO2
  • carbon sequestration
  • FACE experiment
  • N cycling
  • Pinus taeda
KeyWord(s) Plus
  • ATMOSPHERIC CARBON-DIOXIDE
  • WARM-TEMPERATE FOREST
  • SOIL ORGANIC-MATTER
  • PROGRESSIVE NITROGEN LIMITATION
  • FINE-ROOT PRODUCTION
  • SCRUB-OAK ECOSYSTEM
  • PINE FOREST
  • LOBLOLLY-PINE
  • MICROBIAL COMMUNITY
  • ABOVEGROUND BIOMASS
ESI Discipline(s)
  • Environment/Ecology
Web of Science Category(ies)
  • Biodiversity Conservation
  • Ecology
  • Environmental Sciences
Adress(es)

[Hofmockel, Kirsten S.] Iowa State Univ, Dept Ecol Evolut & Organismal Biol, Ames, IA 50011 USA; [Hofmockel, Kirsten S.; McCarthy, Heather R.; Jackson, Robert B.] Duke Univ, Nicholas Sch Environm & Earth Sci, Durham, NC 27708 USA; [Gallet-Budynek, Anne] Boston Univ, Dept Biol, Boston, MA 02215 USA; [Gallet-Budynek, Anne] INRA, UMR TCEM 1220, F-33883 Villenave Dornon, France; [McCarthy, Heather R.] Univ Calif Irvine, Dept Earth Syst Sci, Irvine, CA 92697 USA; [Currie, William S.] Univ Michigan, Sch Nat Resources & Environm, Ann Arbor, MI 48109 USA

Reprint Adress

Hofmockel, KS (reprint author), Iowa State Univ, Dept Ecol Evolut & Organismal Biol, Ames, IA 50011 USA.

Country(ies)
  • France
  • United States
CNRS - Adress(es)
    Accession Number
    WOS:000296137000006
    uid:/7WHWVFCJ
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