Master of Science (MSc)
Biological and Chemical Sciences
Faculty of Science
Kevin J. Stevens
An important symbiotic relationship that forms in wetland environments occurs between plants and arbuscular mycorrhizal fungi (AMF). In terrestrial communities AMF colonization is limited by phosphorus; excessive phosphorus can lead to an uncoupling of the relationship. Few studies have examined the relationship between AMF and phosphorus concentration in wetland plants. The studies that have, found a decrease in AMF colonization at phosphorus concentrations as low as 0.03 mg/L P, however, methodological issues limit the interpretation of these results. To address this, a field and greenhouse study were completed using more realistic exposure conditions, field deployable assays (FDA), and natural intact soil cores that more accurately reflect the soil and soil communities that are present within the Grand River watershed.
In the greenhouse study, Phalaris arundinacea, Veronica anagallis-aquatica and Echinochloa muricata were grown at 10, 30, or 644 µg/L P using with a flow through exposure system. The results showed species-specific responses that were dependent on phosphorous concentration. Phosphorous levels ranging from 0.01-0.03 mg/L P were able to negatively affect the percentage of AMF colonization, for example at the lowest phosphorous concentration Echinochloa muricata had an average AMF colonization of 26% but with increased phosphorous colonization, colonization decreased to approximately 3.5%. The field study utilized the same plant species and showed a significant decrease in AMF colonization at sites with high phosphorous concentrations (85.9-90 µg/L P) compared to the site with low phosphorous concentrations (55.8 µg/L P). In the field, root weight, surface area and length were also significantly lower at locations with high phosphorous concentrations (85.9-90 µg/L P). The outcome of the controlled and field studies showed the range of phosphorus that impacts AMF colonization was between 10-30 µg /L P. Considering the provincial target in Ontario is 30 µg /L P, higher than what is altering AMF associations, additional research is needed to determine how these changes affect plant and mycorrhizal community structure and ecosystem functioning to determine if a change in lower limits for provincial targets is needed.
Tucker, Miriah, "Effects of phosphorus on mycorrhizal colonization of wetland plants under natural and controlled conditions" (2020). Theses and Dissertations (Comprehensive). 2230.
Available for download on Saturday, April 10, 2021