Mycorrhizal ecology on serpentine soils

Abstract

Background: Serpentine ecosystems support different, often unique, plant communities; however, we know little about the soil organisms that associate with these ecosystems. Mycorrhizas, mutualistic symbioses between fungi and roots, are critical to nutrient cycling and energy exchange below ground.

Aims: We address three hypotheses: H1, diversity of mycorrhizal fungi in serpentine soils mirrors above-ground plant diversity; H2, the morphology of mycorrhizas and fungi on serpentine soils differs from that on non-serpentine; and H3, mycorrhizal fungal communities of the same or closely related hosts differ between serpentine and non-serpentine soils.

Methods: This review focuses on whether plant diversity on serpentine soils correlates with the below ground diversity of mycorrhizal fungi.

Results: Studies show that plants and fungi formed abundant ectomycorrhizal and arbuscular mycorrhizal symbioses on and off serpentine soils. No serpentine-endemic fungi were identified. Molecular analyses indicate distinct serpentine isolates for Cenococcum geophilum and for Acaulospora, suggesting adaptation to serpentine soils. While fungal sporocarp assemblages on serpentine sites resembled those off serpentine, fruiting of hypogeous fungi was greatly reduced.

Conclusions: Ectomycorrhizal fungal communities did not differ between soil types; however, arbuscular mycorrhizal communities differed in some cases but not others. The additive response to multiple factors, described as the serpentine syndrome, may explain part of the response by fungi.

Keywords:

• arbuscular mycorrhizas
• Cenococcum geophilum
• ectomycorrhizas
• hypogeous fungi
• Quercus garryana
• Quercus ilex
• serpentine syndrome

Acknowledgements

We thank Jonathan L. Frank, Mariah Moser and Sandra Gladish for fieldwork, morphotyping and molecular analyses; Dr Jad D’Allura for help in confirming serpentine sites; and Dr Paul Sanborn for suggestions with respect to the evolving serpentine literature. Research support was funded, in part, by an NSERC Discovery Grant to H.B.M.

Additional information

Notes on contributors

Darlene Southworth

Darlene Southworth is emeritus Professor of Biology. Her research focuses on mycorrhizal fungi with oaks and the associates of rare hypogeous fungi in southern Oregon.

Linda E. Tackaberry

Linda Tackaberry is a research associate. Her work is on mycorrhizas of Douglas fir on serpentine soils in British Columbia.

Hugues B. Massicotte

Hugues Massicotte is Professor of Forest Biology. His research is on mycorrhizal fungi of achlorophyllous plants and on mycorrhizas of Douglas fir on serpentine soils in British Columbia.