Nitrogen enrichment alters mycorrhizal allocation at five mesic to semiarid grasslands

Nancy Johnson, Diane L. Rowland, Lea Corkidi, Louise M. Egerton-Warburton, Edith B. Allen

Research output: Contribution to journalArticle

272 Citations (Scopus)

Abstract

Arbuscular mycorrhizal (AM) fungi are integral components of grasslands because most plants are associated with interconnected networks of AM hyphae. Mycorrhizae generally facilitate plant uptake of nutrients from the soil. However, mycorrhizal associations are known to vary in their mutualistic function, and there is currently no metric that links AM functioning with fungal colonization of roots. Mycorrhizal structures differ in their physiological and ecological functioning, so changes in AM allocation to intraradical (inside roots) and extraradical (in soil) structures may signal shifts in mycorrhizal function. We hypothesize that the functional equilibrium model applies to AM fungi and that fertilization should reduce allocation to arbuscules, coils, and extraradical hyphae, the fungal structures that are directly involved in nutrient acquisition and transfer to plants. This study compared AM responses to experimental N enrichment at five grasslands distributed across North America. Samples were collected from replicated N-enriched (and some P-enriched) and control plots throughout the growing season for three years. Intraradical AM structures were measured in over 1400 root samples, extraradical hyphal density was measured in over 590 soil samples, and spore biovolume was analyzed in over 400 soil samples. There were significant site X N interactions for spore biovolume, extraradical hyphae, intraradical hyphae, and vesicles. Nitrogen enrichment strongly decreased AM structures at Cedar Creek, the site with the lowest soil N:P, and it increased AM structures at Konza Prairie, the site with the highest soil N:P. As predicted by the functional equilibrium model, in soils with sufficient P, relative allocation to arbuscules, coils, and extraradical hyphae was generally reduced by N enrichment. Allocation to spores and hyphae was most sensitive to fertilization. At the mesic sites, this response was associated with a shift in the relative abundance of Gigasporaceae within AM fungal communities. This study demonstrates that N enrichment impacts mycorrhizal allocation across a wide range of grassland ecosystems. Such changes are important because they suggest an alteration in mycorrhizal functioning that, in turn, may impact plant community composition and ecosystem function.

Original languageEnglish (US)
Pages (from-to)1895-1908
Number of pages14
JournalEcology
Volume84
Issue number7
StatePublished - Jul 2003

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hyphae
grasslands
grassland
nitrogen
spore
soil
spores
mycorrhizal fungi
Gigasporaceae
soil sampling
fungus
ecosystems
mycorrhiza
nutrient
fungal communities
ecosystem function
vesicle
soil structure
mycorrhizae
rangelands

Keywords

  • Arbuscular mycorrhizae
  • Functional equilibrium
  • Grasslands
  • Intersite comparison
  • LTER
  • N:P ratio
  • Nitrogen eutrophication

ASJC Scopus subject areas

  • Ecology

Cite this

Johnson, N., Rowland, D. L., Corkidi, L., Egerton-Warburton, L. M., & Allen, E. B. (2003). Nitrogen enrichment alters mycorrhizal allocation at five mesic to semiarid grasslands. Ecology, 84(7), 1895-1908.

Nitrogen enrichment alters mycorrhizal allocation at five mesic to semiarid grasslands. / Johnson, Nancy; Rowland, Diane L.; Corkidi, Lea; Egerton-Warburton, Louise M.; Allen, Edith B.

In: Ecology, Vol. 84, No. 7, 07.2003, p. 1895-1908.

Research output: Contribution to journalArticle

Johnson, N, Rowland, DL, Corkidi, L, Egerton-Warburton, LM & Allen, EB 2003, 'Nitrogen enrichment alters mycorrhizal allocation at five mesic to semiarid grasslands', Ecology, vol. 84, no. 7, pp. 1895-1908.
Johnson N, Rowland DL, Corkidi L, Egerton-Warburton LM, Allen EB. Nitrogen enrichment alters mycorrhizal allocation at five mesic to semiarid grasslands. Ecology. 2003 Jul;84(7):1895-1908.
Johnson, Nancy ; Rowland, Diane L. ; Corkidi, Lea ; Egerton-Warburton, Louise M. ; Allen, Edith B. / Nitrogen enrichment alters mycorrhizal allocation at five mesic to semiarid grasslands. In: Ecology. 2003 ; Vol. 84, No. 7. pp. 1895-1908.
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