PARENT SESSION
Oral Session #73: Applied Ecology and Ecological Economics. Presiding: J. Hof.
Friday, August 10, 2001. 8:00 AM to 12:00 PM. Hall of Ideas P&Q.
The response of a forested community (Forest Park in Portland, OR) to urbanization.
Broshot-Hamilton, Nancy1, Tinnin, Robert2, 1 2
ABSTRACT- Human activities cause changes in most natural systems. As human populations increasingly expand into forested areas, forests will become more reflective of human influence. I examined changes along an urban-rural forest gradient using 24 randomly selected sites in a naturally regenerating forest (Forest Park in Portland, Oregon). An additional site outside of the park was placed in a forest remnant that did not have any history of logging to serve as a control. The date and type of the last major disturbance (e.g., logging, fire) at each site was estimated using dendrochronology, site observations, and historical archives. Data on tree species composition, dbh, mortality, and diversity (H′) were collected at all 25 sites. Data were analyzed using ANOVA and multiple regression to determine trends of change related to the urban-rural gradient. Many tree variables, especially those related to increasing shade tolerance, were positively correlated with distance from downtown Portland and with the number of houses in the surrounding area. Significantly fewer saplings and small trees of shade tolerant species were located in the park nearest to the city suggesting possible interference with regeneration. The section of the forest nearest the city shows characteristics typical of an earlier successional stage than would be expected from its disturbance history. Possibly some factor of urbanization is interfering with normal successional processes in those sections of the park closest to downtown Portland.
KEY WORDS: forest, urbanization, succession, tree