The Swain Mountain Experimental Forest was formally designated on March 22,
1932, as a place for field studies and demonstration of forest management practices
in the true-fir types of California. Chosen specifically for the quality and
extent of the fir timber present, the 2,492-ha forest occupies all of Swain
Mountain, a volcanic cone composed of vesicular andesite and ash, with elevations
from 1,737 to 2,149 m. Stand volume can be high, up to 2,058 m3/ha
on one 1.6-ha block, though the virgin stands more commonly contain 840-1,120
Swain Mountain largely sat idle for about 20 years until preparation for an
active program of regeneration research began in the early 1950s with forest-type
mapping and construction of the initial road system. Initial research was to
determine factors related to wind damage in the old-growth stands and to develop
criteria for selection of wind-firm seed trees. Seed dispersal was measured
for both red and white firs. Relationships between natural regeneration and
site factors such as soil temperature and moisture, insolation intensity, site
preparation, and competing vegetation were explored. Snow surveys were taken
for nearly 15 years in the clearcut and unlogged stands. Cone production in
uncut stands and along clearcut strips was followed for 16 years.
The second round of research cutting in the early 1970s again was centered
on natural regeneration and the impact of shelterwood density and clearcut size
and shape. During the 1960s and 1970s, studies of the effects of dwarf mistletoe
and fertilization began, as did studies of growth and yield of mixed fir stands.
Long-term studies of response of severely suppressed true-fir to release from
overstory competition were installed. The information gained from this work
constitutes the basis for true-fir management in California.
The third and current period of heavy cutting is to extend the shelterwood
research results to operationally large areas and create extensive acreage of
fir regeneration for future research. To these ends, about one-third of Swain
Mountain has been regenerated through shelterwood cutting.
The climate can be classified as cool and moist even though there is a 4- to
5-month summer dry spell. Precipitation ranges from 1,243 to 1,270 mm annually,
almost all of which falls between October and March. Eighty percent of the moisture
falls as snow, and snowpacks of 3 to 4 m are common in February. In exceptionally
wet years with late spring snows, drifts can persist until late July. Between
April/May and October, precipitation is negligible, coming from scattered thunder
showers. Winter temperatures generally do not fall below -23 °C and summer
temperatures only occasionally exceed 29 °C. Average monthly minimum and
maximum air temperatures range from -17 ° to 4 °C for January and
from 4 ° to 27 °C for July.
Soils are 0.6 to 2.4 m deep and are generally well drained except in association
with small "shoestring" meadows. The soils are derived in place from weathering
of the andesite and associated ash. The lava flows that formed the mountain
are occasionally visible at the surface. Soil series have not been mapped. Site
quality varies but in general is good; site index is 150 at 300 years.
Forest cover types on the SMEF include large areas of red fir (SAF 207), white
fir (SAF 211), and small areas of lodgepole pine (SAF 218) cover types. White
fir predominates at the low to middle elevations (1,737 to 1,890 m), with the
proportion of red fir increasing with increasing elevation to the top at 2,149
m. Together, the true fir occupies 1,821 ha. Lodgepole pine grows throughout
the forest associated with meadows, but forms pure stands only at the lowest
elevations and in areas of shallow soils or high water tables. There are 178
ha in lodgepole pine. About 445 ha on the south slope of the mountain are occupied
by an old brushfield that has been planted with ponderosa and Jeffrey pines.
Long-Term Data Bases
A true-fir levels-of-growing-stock installation at Swain Mountain has been
maintained since 1976, with remeasurements taking place every 5 years.
Research, Past and Present
In addition to the current research on true-fir growth and yield, research
has been conducted on natural regeneration, pathology, site preparation, and
effects of insects on cone crops.
Collaborators include the Almanor Ranger District, Lassen National Forest.
Swain Mountain provides a place to study the true-fir type common at higher
elevations in the northern Sierra and southern Cascades. Many acres of shelterwood
provide opportunities to study the dynamics of young stands of white and red
The Swain Mountain is located 13 km north of Westwood, California. It can be
reached via a paved road that is cleared of snow all winter. Access between
mid- December and early May is limited to snowmobile, skis, or similar transportation.
All of the current 41.8 km of all-weather road are accessible by automobile
when free of snow.
The USDA Forest Service's Pacific Southwest Research Station maintains barracks
and office space for up to 15 people at the nearby Bogard Work Center on the
Eagle Lake Ranger District (about a 25 minute drive from the forest). These
facilities are primarily for the work at Blacks Mountain Experimental Forest
but are available for work at Swain Mountain also.
Lat. 40°25´ N, long. 121°6´ W
Contact Information 1
Swain Mountain Experimental Forest
USDA Forest Service
Pacific Southwest Research Station
3644 Avtech Parkway
Redding, CA 96002
Tel: (530) 226-2530