Post-Grant Reports


Effect of Urbanization on the Avian Community and Tree Seedling Growth and Mortality in an Urban Forest, Forest Park in Portland, Oregon

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Ecology and Evolutionary Biology | Environmental Monitoring | Forest Management | Spatial Science


Two students (Terran Sobel-Smith and Carli McCormick) worked with me over the summer. We completed three bird counts at each of my sites in Forest Park during the month of June. We collected data on growth, predation, and survival of western red cedar seedlings planted in 2005 at nine conifer recruitment sites in Forest Park. We also measured ambient light, soil moisture, soil electroconductivity (ECP), soil temperature, and soil pH around every seedling in an attempt to examine potential causes for differences in tree response. To determine whether the low number of seedlings in Forest Park was “normal”, we added three control sites in the Mount Hood National Forest above Estacada.

We found significantly more seedlings at the control sites than at any site in Forest Park. We found that seedlings grew significantly better (defined by increased height and basal diameter) in the middle and far sections of Forest Park than in the city section. We also found grazing by deer and elk to be significantly greater in the far section, meaning the reduced growth in the city section was not related to predation. Tree mortality was greatest in the middle section of the park. None of the abiotic factors we examined (e.g., light, soil moisture, soil ECP, soil temperature, and soil pH) correlated with seedling growth or mortality. Our results suggest air pollution may be related to the lack of seedlings in urban forests. Terran, Carli, and I presented our findings at the annual UERC (Urban Ecology Research Consortium) symposium on February 8, 2016 in Portland, Oregon. We are in the process of writing a paper we will submit to Quercus (and perhaps another refereed journal). Terran, Carli, and I will present a poster about our findings at the Linfield College Student Science and Creative Projects Symposium.


This research was conducted as part of a Linfield College Student-Faculty Collaborative Research Grant in 2015, funded by the Office of Academic Affairs.

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