Nitrogen cycling during seven years of atmospheric CO2 enrichment in a scrub oak woodland

Bruce A Hungate, Dale W. Johnson, Paul Dijkstra, Graham Hymus, Peter Stiling, J. Patrick Megonigal, Alisha L. Pagel, Jaina L. Moan, Frank Day, Jiahong Li, C. Ross Hinkle, Bert G. Drake

Research output: Contribution to journalArticle

66 Citations (Scopus)

Abstract

Experimentally increasing atmospheric CO2 often stimulates plant growth and ecosystem carbon (C) uptake. Biogeochemical theory predicts that these initial responses will immobilize nitrogen (N) in plant biomass and soil organic matter, causing N availability to plants to decline, and reducing the long-term CO2-stimulation of C storage in N limited ecosystems. While many experiments have examined changes in N cycling in response to elevated CO2, empirical tests of this theoretical prediction are scarce. During seven years of postfire recovery in a scrub oak ecosystem, elevated CO2 initially increased plant N accumulation and plant uptake of tracer 15N, peaking after four years of CO2 enrichment. Between years four and seven, these responses to CO2 declined. Elevated CO2 also increased N and tracer 15N accumulation in the O horizon, and reduced 15N recovery in underlying mineral soil. These responses are consistent with progressive N limitation: the initial CO2 stimulation of plant growth immobilized N in plant biomass and in the O horizon, progressively reducing N availability to plants. Litterfall production (one measure of aboveground primary productivity) increased initially in response to elevated CO2, but the CO2 stimulation declined during years five through seven, concurrent with the accumulation of N in the O horizon and the apparent restriction of plant N availability. Yet, at the level of aboveground plant biomass (estimated by allometry), progressive N limitation was less apparent, initially because of increased N acquisition from soil and later because of reduced N concentration in biomass as N availability declined. Over this seven-year period, elevated CO2 caused a redistribution of N within the ecosystem, from mineral soils, to plants, to surface organic matter. In N limited ecosystems, such changes in N cycling are likely to reduce the response of plant production to elevated CO2.

Original languageEnglish (US)
Pages (from-to)26-40
Number of pages15
JournalEcology
Volume87
Issue number1
DOIs
StatePublished - Jan 2006

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scrub
shrublands
woodlands
woodland
Quercus
organic horizons
nitrogen
ecosystems
mineral soils
tracer techniques
soil organic matter
ecosystem
plant growth
uptake mechanisms
biomass
allometry
aboveground biomass
plant response
oak
primary productivity

Keywords

  • N
  • Nitrogen cycling
  • Progressive nitrogen limitation
  • Rising atmospheric CO

ASJC Scopus subject areas

  • Ecology

Cite this

Nitrogen cycling during seven years of atmospheric CO2 enrichment in a scrub oak woodland. / Hungate, Bruce A; Johnson, Dale W.; Dijkstra, Paul; Hymus, Graham; Stiling, Peter; Megonigal, J. Patrick; Pagel, Alisha L.; Moan, Jaina L.; Day, Frank; Li, Jiahong; Hinkle, C. Ross; Drake, Bert G.

In: Ecology, Vol. 87, No. 1, 01.2006, p. 26-40.

Research output: Contribution to journalArticle

Hungate, BA, Johnson, DW, Dijkstra, P, Hymus, G, Stiling, P, Megonigal, JP, Pagel, AL, Moan, JL, Day, F, Li, J, Hinkle, CR & Drake, BG 2006, 'Nitrogen cycling during seven years of atmospheric CO2 enrichment in a scrub oak woodland', Ecology, vol. 87, no. 1, pp. 26-40. https://doi.org/10.1890/04-1732
Hungate, Bruce A ; Johnson, Dale W. ; Dijkstra, Paul ; Hymus, Graham ; Stiling, Peter ; Megonigal, J. Patrick ; Pagel, Alisha L. ; Moan, Jaina L. ; Day, Frank ; Li, Jiahong ; Hinkle, C. Ross ; Drake, Bert G. / Nitrogen cycling during seven years of atmospheric CO2 enrichment in a scrub oak woodland. In: Ecology. 2006 ; Vol. 87, No. 1. pp. 26-40.
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