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Title: Nitrogen availability and colonization by mycorrhizal fungi correlate with nitrogen isotope patterns in plants
Authors: Hobbie, EA
Issue Date: 2003
Source: NEW PHYTOLOGIST, 157(1). p. 115-126
Abstract: Nitrogen isotope (delta(15)N) patterns in plants may provide insight into plant N dynamics. Here, two analytical models of N-isotope cycling in plants and mycorrhizal fungi were tested, as dominant plants in many forest ecosystems obtain most of their N through intereactions with mycorrhizal fungi. Fungi were treated either as a single well-mixed N pool, or as two N pools (one available, plus one not available, for transfer to the host). Models were compared against complete biomass and (15) N budgets from culture studies of nonmycorrhizal and ectomycorrhizal Pinus sylvestris (colonized with Suillus luteus or Thelephora terrestris) grown exponentially at low and high N supply. Fungal biomass and N increased at low N relative to high N supply, whereas needle delta(15) N decreased. Needle delta(15)N correlated strongly and negatively with biomass of extraradical hyphae. Our data and models suggest that low plant delta(15) N values in low productivity and N-limited environments result partly from high retention of (15) N-enriched N by mycorrhizal fungi; this retention was driven by increased C flux to fungi under N-limited conditions. The two-pool model of fungal N accounted for greater variability in plant delta N-15 than the one-pool model. Plant delta (15) N patterns may indicate relative allocation of fixed C from plants to mycorrhizal fungi under some conditions. Studies are needed on whether patterns observed in culture can be applied to interpret field measurements of delta(15) N.
Notes: Max Planck Inst Biogeochem, D-07701 Jena, Germany. Limburgs Univ Ctr, B-3590 Diepenbeek, Belgium.Hobbie, EA, Univ New Hampshire, Complex Syst Res Ctr, Morse Hall, Durham, NH 03824 USA.
Keywords: nitrogen isotope (delta N-15) patterns; Pinus sylvestris; mycorrhizal fungi; N cycling; C flux; biomass
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ISSN: 0028-646X
e-ISSN: 1469-8137
DOI: 10.1046/j.1469-8137.2003.00657.x
ISI #: 000179945400013
Category: A1
Type: Journal Contribution
Validations: ecoom 2004
Appears in Collections:Research publications

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