Date of Award
Bachelor of Science (B.S.) in Biology and University Honors
Plant morphology, Leaves -- Aging -- Effect of urban heat island on, Trees -- Oregon -- Portland -- Phenology, Acer macrophyllum, Norway maple
Due to the heterogeneity of the urban heat island, we can think of the variable influence of urbanization on air temperature as more of an urban heat mosaic. Climate change has caused a resurgence of interest in the way temperature affects how organisms, such as street trees, undergo cyclic changes in their life cycle. Such changes include budburst or, less commonly, timing of senescence. Little is known about how the urban heat mosaic could be affecting the phenology of different urban trees. Because street trees are one of the more prominent ecosystem engineers of the urban landscape, variable influences of temperature on tree phenology could impact urban ecosystem ecology and human health. This study investigated the timing of senescence for Acer macrophyllum (Bigleaf maple) and Acer platanoides (Norway maple) in warm and cool zones in Portland, Oregon. Senescence was characterized as the changing of leaf color, and a total of thirty-two trees were observed over the course of October and November to track senescence. These observations showed a significantly late senescence time of about three days for Norway maples in warm zones (p= 0.13). Though it was hypothesized that the cool zones would senesce sooner than the warm zones, this was only the case for Norway maples, as Bigleaf maples had cool zones senesce about two days later than the warm zones (p= 0.14). This differential response may be explained by an increased vulnerability of Bigleaf maple to urbanization and heat in general. More research is needed to understand how different street tree species respond to variation in environmental conditions and respective socioecological implications.
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Smith, Jeffrey D., "Impact of the Urban Heat Mosaic on the Leaf Senescence in Two Acer Species" (2020). University Honors Theses. Paper 833.