Results :: Individual ETD
Title: Arbuscular Mycorrhizae in Yellowstone National Park Thermal Soils: Host Plant, Fungal Inoculum, Soil pH, and Elevated Temperature Effects on Symbiosis Function
Creator: Bunn, Rebecca Anne
Description: Arbuscular mycorrhizae (AM) are frequently described as a textbook example of a mutualistic symbiosis between a plant and fungus. However, we now understand that AM fungi are not always beneficial to their host plants. By requiring host plant photosynthate in exchange for potential benefits, the symbiosis varies along a continuum from mutualistic to parasitic. Examining AM function in extreme environments may increase our understanding of how the balance between symbionts is achieved, and if it is altered in the presence of strong abiotic stresses. Thermal soils offer a unique opportunity to study this symbiosis across dramatic gradients of temperature, nutrient availability, and element toxicity within a small geographic area. This work has documented the occurrence of AM in multiple thermal areas across Yellowstone National Park, despite conditions that are limiting to plant growth, including acidic soils and elevated soil temperatures. Furthermore, viable AM fungal propagules were observed across environmental gradients, suggesting new plants would have access to AM fungi despite sparse vegetation and unfavorable soil conditions. This research has also examined AM effects on plant growth across abiotic gradients present in thermal soils. At extremes in soil pH, AM did not increase size or reproductive ability of host plants, but did reduce uptake of a potentially toxic element. In elevated soil temperatures, AM benefited both plants adapted to elevated temperatures and those that grow across a broader range of habitats, although the effects varied. Mycorrhizal extraradical hyphal length density universally increased in environments where elevated temperatures limited root growth, potentially compensating for reduced root development. Finally, we found no evidence that thermal AM fungal communities are adapted to uniquely benefit host plants in acidic, alkaline, or elevated temperature soils. These results indicate that AM function is altered across gradients of soil temperature, but not pH. Lastly, in elevated temperatures, the balance between the symbionts appears to involve an increase in extraradical hyphae production by the fungus, and likely, a corresponding increase in photosynthate allocation from the host plant. This ultimately suggests that in addition to other documented AM effects, AM may compensate for reduced root function in soils inhospitable to plant growth.
Location: http://etd.lib.montana.edu/etd/2004/bunn/BunnR0805.pdf
Document Type: Doctoral
Contributor: Zabinski, Catherine A. (committee chairperson)
Committee Members: Steve Cherry, John Wraith, Matt Lavin, William Inskeep
Department: Land Resources & Environmental Sciences
Publisher: Montana State University
Date Created: 2004-08-15
Access Rights: Accessible under copyright for educational purposes.