Post-Grant Reports


Seedling Growth and Survival Relative to Soil Characteristics

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Ecology and Evolutionary Biology | Environmental Indicators and Impact Assessment | Environmental Monitoring | Environmental Sciences | Forest Management | Soil Science


In previous work, I found that urban forests have few to no seedlings and saplings compared to more rural forests. To determine possible reasons for this finding, William McCuen helped me examine invasive earthworms and soil characteristics at my permanent research sites in Forest Park and control sites in the Mount Hood National Forest. Austen Bassler, an Oregon City high school student, and I collected earthworms and measured soil characteristics, as well as located and measured all living and dead seedlings and saplings at my permanent research sites. We measured the depth of the O horizon (the leaf litter) and measured 24-hour CO2 production from soil collected at the sites to determine respiration rates. We also examined seedling roots for the presence and/or absence of mycorrhizael fungi.

The earthworm data collected last summer, combined with that collected the previous summer, showed no correlation between worm density or biomass and urbanization, suggesting earthworms are not related to the loss of seedlings at urban sites. We found the depth of the O horizon and the amount of CO2 to be significantly higher at rural sites than in the urban forest. However, due to equipment failure, we did not get all the soil analyzed. We found the density, total diameter, and total height of seedlings and saplings to be significantly greater at the control sites than at any urban location in both 2013 and 2018. Although these variables appeared to be lower in 2018 than in 2013, the differences were not significant. The five-year time frame was not long enough to reveal significant changes. Our examination of previously collected seedling roots revealed the presence of mycorrhizae; however, our methods were not adequate to give precise quantitative data.


This research was conducted as part of a Linfield College Student-Faculty Collaborative Research Grant in 2018, funded by the Office of Academic Affairs.

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