Interactions of arbuscular mycorrhizal fungi, critical loads of nitrogen deposition, and shifts from native to invasive species in a southern California shrubland

Edith B. Allen, Louise M. Egerton-Warburton*, Bridget E. Hilbig, Justin M. Valliere

*Corresponding author for this work

Research output: Contribution to journalReview articlepeer-review

17 Scopus citations

Abstract

Anthropogenic nitrogen (N) deposition and invasive species are causing declines in global biodiversity, and both factors impact the diversity and functioning of arbuscular mycorrhizal (AM) fungi. Shifts in arbuscular mycorrhizal fungal (AMF) communities can generate feedback to native plants and affect their success, as was observed in California’s coastal sage scrub, which is a Mediterranean-type shrubland threatened by invasive grasses. As vegetation-type conversion from native shrubland to exotic annual grassland increased along a gradient of increasing N deposition, the richness of native plant species and of spore morphotypes decreased. Rapid declines in all plant and fungal values occurred at the critical load (CL) of 10–11 kg N·ha−1·year−1, indicating thatAM fungi respond to the same environmental signals as the plants, and can be used to assess CL. Shrub root colonization also decreased along theNgradient, but colonization of the invasive grass was dominated by a fineAMFendophyte that was unresponsive to elevated N. A greenhouse experiment to assess AMF functioning showed that the native shrub Artemisia californica Less. had a negative growth response to an inoculum from high-N but not low-N soils, whereas the invasive grass Bromus rubens L. had a positive response to both inocula. Differential functioning of AM fungi under N deposition may in part explain vegetation-type conversion and the decline of this native shrubland.

Original languageEnglish (US)
Pages (from-to)425-433
Number of pages9
JournalBotany
Volume94
Issue number6
DOIs
StatePublished - Jan 27 2016

Keywords

  • Fine endophyte
  • Glomus tenue
  • Nitrogen critical load
  • Vegetation-type conversion

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics
  • Ecology
  • Plant Science

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