Evidence for mutualist limitation

The impacts of conspecific density on the mycorrhizal inoculum potential of woodland soils

Kristin E. Haskins, Catherine A Gehring

Research output: Contribution to journalArticle

24 Citations (Scopus)

Abstract

The ability of seedlings to establish can depend on the availability of appropriate mycorrhizal fungal inoculum. The possibility that mycorrhizal mutualists limit the distribution of seedlings may depend on the prevalence of the plant hosts that form the same type of mycorrhizal association as the target seedling species and thus provide inoculum. We tested this hypothesis by measuring ectomycorrhizal (EM) fine root distribution and conducting an EM inoculum potential bioassay along a gradient of EM host density in a pinyon-juniper woodland where pinyon is the only EM fungal host while juniper and other plant species are hosts for arbuscular mycorrhizal (AM) fungi. We found that pinyon fine roots were significantly less abundant than juniper roots both in areas dominated aboveground by juniper and in areas where pinyon and juniper were co-dominant. Pinyon seedlings establishing in pinyon-juniper zones are thus more likely to encounter AM than EM fungi. Our bioassay confirmed this result. Pinyon seedlings were six times less likely to be colonized by EM fungi when grown in soil from juniper-dominated zones than in soil from either pinyon-juniper or pinyon zones. Levels of EM colonization were also reduced in seedlings grown in juniper-zone soil. Preliminary analyses indicate that EM community composition varied among sites. These results are important because recent droughts have caused massive mortality of mature pinyons resulting in a shift towards juniper-dominated stands. Lack of EM inoculum in these stands could reduce the ability of pinyon seedlings to re-colonize sites of high pinyon mortality, leading to long-term vegetation shifts.

Original languageEnglish (US)
Pages (from-to)123-131
Number of pages9
JournalOecologia
Volume145
Issue number1
DOIs
StatePublished - Aug 2005

Fingerprint

woodland soils
woodland
inoculum
seedling
pinyon-juniper
seedlings
soil
fungus
fine root
bioassay
bioassays
mortality
fungi
mycorrhizal fungi
host plant
community composition
woodlands
colonization
host plants
drought

Keywords

  • Bioassay
  • Drought
  • Juniperus monosperma
  • Pinus edulis
  • Pinyon-juniper woodland

ASJC Scopus subject areas

  • Ecology

Cite this

Evidence for mutualist limitation : The impacts of conspecific density on the mycorrhizal inoculum potential of woodland soils. / Haskins, Kristin E.; Gehring, Catherine A.

In: Oecologia, Vol. 145, No. 1, 08.2005, p. 123-131.

Research output: Contribution to journalArticle

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