Honors Theses


Ryan McEwan



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Honors Thesis


Pyrus calleryana is quickly becoming one of the most problematic invasive species in the Eastern and Central part of the United States. Pyrus calleryana is an early successional species that quickly proliferates in highly disturbed soils such as old fields and younger prairies. Currently, this species poses a large threat to land managers as it changes the successional trajectories of forest and prairie systems, creating new novel ecosystems. Pyrus calleryana outcompetes most native early successional species and is relatively understudied. The mechanism in which Pyrus calleryana utilizes to dominate ecosystems are not fully understood, but one theory is Pyrus calleryana extended leaf phenology in comparison to other native woody successional species. We hypothesized that Pyrus calleryana has a longer leaf phenology than two native woody species, Populus deltoides and Plantanus occidentalis. We observed these three species at 3 sites in Dayton, OH from December 2019 to November of 2020. A frost event in May also gave us the opportunity to understand frost tolerance with these species. We found that Pyrus calleryana began leafing out almost a month before its native competitors in the spring and kept its leaves on significantly longer than both P.deltoides and P.occidentalis (p<0.001) throughout the fall. During the frost event, almost every single leaf on P.occidentalis died and almost 70% of the leaves on P.deltoides were damaged. However, Pyrus calleryana only had damage on 6% of its leaves. Our experiment suggests that Pyrus calleryana uses an extended leaf phenology as a mechanism to outcompete native successional species as it is able to photosynthesize longer, which builds up carbon and nutrient reserves, and is able to withstand frost events.

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Undergraduate research



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