Ectomycorrhizal fungi form mutualistic symbioses with both conifer and broadleaf tree species. These associations benefit the trees by assisting with nutrient uptake and nitrogen fixation.
Mycorrhizal fungi are the beneficial fungi which can form symbiotic relationships with the plant roots of nearly all evergreen species and approximately 60% of deciduous plants. This symbiotic relationship provides plant roots with additional surface area with which to absorb water and nutrients and allows the fungus to feed on sugars and starches produced by the plant. Additionally, mycorrhizae are able to mobilize tightly bound nutrients from the soil such as phosphorus, nitrogen, zinc, iron, calcium and magnesium, which may have not been otherwise obtainable by the plant. Water uptake and utilization can also be improved through this alliance.
Invasive plant species wreak havoc on ecosystems by outcompeting native species and replacing them their niche, which causes cascading negative effects throughout the trophic web. Recently research has been conducted regarding the effect invasive garlic mustard, Alliaria petiolata, has on the symbiotic relationship between oak species and their fungal partners. The study tested whether ectomycorrhizal fungi (ECM) associated with northern red oak, Quercus rubra, was lower in the presence of the invasive garlic mustard.
The research quantified ECM colonization, identified species and compared composition in forests with varying densities of garlic mustard. The results revealed that oak stands with higher densities of garlic mustard had lower colonization and diversity of ECM. The composition of ECM also varied amongst stands of trees. Red oak seedlings in stands with a moderately dense stands of garlic mustard had marginally less ECM than those at sites with no garlic mustard. The findings from this study suggest that there is a negative correlation between invasive garlic mustard and ectomycorrhizal fungi colonization. This can result in long-lasting changes to forest community composition and possible difficulty in restoration following invasive species removal.
(Steven M. Castellano and David L. Gorchov, “Reduced Ectomycorrhizae on Oak Near Invasive Garlic Mustard” Northeastern Naturalist 19(1):1-24. 2012)
