Date Thesis Awarded
Honors Thesis -- Access Restricted On-Campus Only
Bachelors of Science (BS)
This study examined how American chestnut seedling performance is influenced by mycorrhizal fungi colonization and interspecific competition from red oak seedlings. Over a century ago, the American chestnut was a dominant tree species, estimated to cover 25-50% of the canopy in eastern deciduous forests. Chestnut populations have now greatly declined to the rise of chestnut blight, a disease induced by Cryphonectria parasitica infection. Chestnut restoration research has gained success over time and reintroduction has progressively become an attainable goal. Analyzing the effects of mycorrhizal fungi associations and competition on chestnut performance provides a better understanding on how chestnuts will respond to the current ecosystem, and how other species will interact with introduced chestnuts. For this outdoor greenhouse study, chestnuts and red oaks were planted in pots with treatments that varied by competitive factors and mycorrhizae presence, as well as mycorrhizal soil origin. Over the five month growing season, data on plant growth was collected. By the end of the season, data on biomass and mycorrhizal colonization was collected as well. Our analysis revealed that American chestnuts exhibited greater change in height, change in diameter, aboveground biomass, and belowground biomass compared to red oaks. American chestnuts and red oaks responded to competition differently from each other. American chestnuts grown with a competitor experienced smaller changes in diameter and aboveground biomass compared to chestnuts grown without a competitor. Red oaks grown with a competitor had greater belowground biomass than those grown without a competitor. Mycorrhizal abundance colonization revealed that overall, roots in mycorrhizae-rich treatments had greater percent colonization compared to roots in sterile treatments. Roots grown in fungicide-treated soils had an intermediate level of colonization that was not significantly different from roots grown in mycorrhizae-rich or sterile soil. Overall, competition presence was related to increased percent colonization, suggesting that higher initial root density in pots may be linked to increased likelihood of colonization. Although some soil treatments demonstrated differences in percent colonization for both red oak and chestnut seedlings, linear regression models revealed that percent colonization was not correlated with chestnut or red oak growth. These results may imply that the differences in mycorrhizal colonization, though statistically significant in some soil treatments, may not be biologically significant enough to induce growth responses. Additionally, lack of growth response may be due to resource abundance within the study, as plants exhibit greater reaction to mycorrhizal fungi when grown in a resource-scarce environment.
Trani, Olivia Ryan, "Implications of Mycorrhizae and Seedling Competition for American Chestnut Restoration" (2016). Undergraduate Honors Theses. William & Mary. Paper 885.
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