|Abstract or Summary
- This study has been concerned with the patterns of vegetative
changes which occur during the first five years following logging and
burning on Douglas-fir clear cuts. Knowledge of the successional sequence
in the coastal forests of western Oregon is of primary importance
to those concerned with the management of this resource. From the more
theoretical point of view, there are many unique features associated
with this type of vegetation of special interest to the ecologist. Published
accounts of studies in Oregon and Washington have been of a
generalized nature. None have approached a localized area with the
degree of intensity attempted in this study.
Due to its close proximity to Oregon State University and the cutting
and burning history of the area, the Mary's Peak Watershed has
been especially suitable for this study.
Mary's Peak is the highest point of the Oregon Coast range having
an elevation of 4,097 feet. The Corvallis watershed is located on the
eastern slope of the peak and includes both the Rock Creek and Griffith
Creek drainages. The area is about five miles long east and west by
four miles north and south. The area is managed as a unit by the United
States Forest Service.
Due to the marine influence, the area has a humid climate averaging
approximately 65 inches of precipitation annually with an annual
mean temperature of approximately 52°F. Soils are basaltic in origin
and are primarily clay loam in texture.
In 1950, an epidemic of Douglas fir bark beetles made necessary
a program of development which included cutting of dead and infected
trees and establishing a road system. Cutting was restricted to small
The vegetation in the study area is a Douglas fir-vine maple association.
Gaultheria shallon and Berberis nervosa dominate the forest
floor with traces of Castanopsis, Corylus, and Cornus.
Study plots were located on nine clear cut and burned areas ranging
in elevation from 1,300 to 2,800 feet and including north, south, and
Nineteen study plots, which were 100 x 100 feet, were established
in uniform vegetative areas. Plots were also established in the undisturbed
areas adjacent to the clear cuts for comparative purposes.
Vegetative sampling was done using a device called an ocular point
frame which provided a reliable indication of vegetative cover. Sampling
was done in both the spring and fall on the second, third, fourth,
and fifth years following burning. The stable undisturbed vegetation
was sampled only once.
Results of the five-year study showed a general increase in total
number of plant species. The average total vegetative cover rose abruptly
the third, fourth, and fifth years. An analysis indicated that
south exposed plots had the greatest vegetative cover the first five years
after burning. East plots ranked second and north plots third. By the
fourth year, average cover values on clear cut areas exceeded the
cover values of understory vegetation on the adjacent uncut forest.
Analysis of data regarding seasonal variation indicated sharp decreases
in total cover from spring to fall during the first three years.
Increasing amounts of perennial vegetation during the fourth and fifth
years reduced this seasonal variation markedly.
In terms of mean cover trends, the annual herb, Senecio sylvaticus,
dominated the second year; Lotus stipularis and Circium vulgare, the
third; Lotus and Holcus lanatus , the fourth and fifth. All plant species
indicated a wide range of cover values on the plots sampled. Some
consistent trends in the sequence of cover dominance are noted.