Post-Grant Reports


Sabbatical Leave Report

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Ecology and Evolutionary Biology | Environmental Indicators and Impact Assessment | Environmental Monitoring | Environmental Studies | Forest Biology | Forest Management


I have been examining the effects of urbanization on forested areas in the Portland, Oregon area since 1993. My early work focused on the plant and avian (bird) communities. That initial study showed changes that correlated with urbanization. A follow-up study in 2003 at my same sites showed higher than normal tree mortality, especially for seedlings and saplings. A lack of young trees (i.e., recruitment) combined with high tree mortality can dramatically change the structure and function of the future forest. In 2013, I did another complete inventory at my 25 sites in Forest Park and added three locations in the Mount Hood National Forest as control sites. Data from these sites has revealed the lack of seedlings to be an urban issue. I believe the changes I am seeing in forest structure are being driven by air pollution, mostly nitrogen oxides from transportation sources. Most of my research has been accomplished through the aid and assistance of many Linfield undergraduate students. My main goal for my sabbatical was to write a paper on the changes in the urban tree community. That paper is in an almost finished draft form; however, I realized I was lacking critical information for a solid paper and so focused last summer on collecting data that would make my paper much stronger.


This research was conducted as part of a sabbatical leave in 2019.

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