|Abstract or Summary
- In 1967 an investigation seeking to understand the disturbance
effects produced by broadcast slash burning was conducted on Douglas
fir clear-cuts in the Harlan area of the Siuslaw National Forest. Specifically,
this study was concerned with the effects disturbance has
on the growth (spatial) patterns and the replacement (time) patterns
of the plant species found in the early successional stages.
The study was conducted on two Douglas fir clear-cuts, one
logged in 1966 and slash burned in 1967 and the other was logged in
1965 and slash burned in 1966. All sampling was done in 1968; one
and two years after slash burning. The disturbance conditions were
defined as being unburned or burned, and five 15' x 15' plots were
placed on unburned soil sites and five 15' x 15' plots were also
placed on burned soil sites on both clear-cuts, creating a two-year
successional sequence. Each plot was subdivided into 25 3' x 3' subplots, 11 of these subplots randomly selected to be sampled. Each
subplot was then divided into nine 1' x microplots, giving a total of
99 microplots per plot. Frequency data on the occurring species was
obtained by counting the number of subdivisions within which a specie
occurred and expressing this as a percentage of the total number of
Tabular ordination of frequency values for presenting and newly
established species according to the two disturbance conditions (burned
and unburned) provide a basis for an evaluation of the relative tolerance
of these species to microenvironments within the clear-cut. Species
preferring burned sites one year after burning include Senecio
sylvaticus, Funaria hygrometrica, Montia sibirica, Senecio jacobea,
Epilobium adenocaulon, Sonchus asper, and Erechites prenanthoides.
Two years after burning Epilobium minutum may be added to the
species listed above.
There also was a group of species found to prefer the unburned
sites which result from the mechanical removal of logs. Species found
consistently in this situation on the clear-cut, sampled two years after
logging (one year after broadcast burning on the clear-cut) include
Agrostis exarata, Rubus parviflorus, Carex festivilla, Crepis setosa,
and Hypochoeris radicata.
For disturbed but unburned locations within the clear-cut three
years after cutting (two years after broadcast burning on the clear-cut), Luzula campestris and Holcus lanatus may be added to the above list.
A wide variety of remnant plant assemblages and microsites are
characteristic of the aftermath of logging and burning on clear-cuts--particularly during the first years following disturbance. A sample
ordination of microsites according to frequency of occurrence of
plant species provides a basis for comparing the relative compatibility
of a species to logging and burning effects. This limited analysis
sugests a relatively narrow place and time niche requirement of
certain plant species occupying Douglas fir clear-cuts during the first
three years following logging and burning.