Pringle Falls Experimental Forest and Research Natural Area
Falls Experimental Forest is a diverse natural laboratory within
the Deschutes National Forest in central Oregon. It was formally
established in 1931 as a center for silviculture, forest management,
and insect and disease research in ponderosa pine forests east of
the Oregon Cascade Range. Pringle Falls is maintained by the Pacific
Northwest Research (PNW) Station for research and education in ecosystem
structure and function and for demonstration of forest management
techniques. It provides outstanding examples of undisturbed and
managed ponderosa pine, lodgepole pine, and higher elevation mixed
conifer forests occurring on 6,600-year-old aerially deposited Mount
Mazama pumice and ash common throughout central and south-central
Pringle Falls was the first experimental forest to be established by the PNW. Thornton T. Munger, first director of the Station, selected
the 3,043-ha site of the Pringle Butte unit in 1914. Munger was a colleague and long-time friend of Gifford Pinchot, first Chief
of the Forest Service. Existing headquarters buildings were constructed between 1932 and 1934. The 3,535-acre Lookout Mountain unit was
added in 1936 for a total of 4,475 ha. Pringle Falls Research Natural Area, within the Pringle Butte unit of the experimental forest,
provides a protected area for nondestructive research.
The climate of Pringle Falls is continental, modified by proximity of the Cascade Range to the west and the
Great Basin Desert to the east. Most precipitation occurs as snowfall. Annual precipitation averages 610 mm on
Pringle Butte and more than 1,020 mm on Lookout Mountain. Daytime high temperatures in the summer
range from 21 to 32 °C. Summer nights are cool and frosts can occur throughout the growing season.
Pringle Falls is characteristic of low-elevation forests within the High Cascades physiographic province.
Terrain is generally flat or gently rolling, dotted with small volcanic peaks and cinder cones. Pringle Butte, the
oldest known geologic formation in the area, is a 5-million-year-old shield volcano rising nearly 305 m above
the surrounding basin. More recent deposits are sand and silt sediments of the La Pine Basin, overlain with sands
and gravels deposited by glacial outwash from the Cascade Range. Lookout Mountain, the highest point in
Pringle Falls (1,592 m), is a 300,000-year-old shield volcano resting on La Pine sediments. Overlaying the
entire area is a 0.5- to 2-m-thick layer of dacite pumice and ash resulting from the explosion of Mount Mazama
(now Crater Lake) nearly 6,600 years ago. Soils derived from Mazama pumice and ash have only a thin
weathered surface layer. Most of the soil profile is undeveloped, with low organic matter content, low
nitrogen, sulfur, and phosphorus content, and high porosity. Daytime to nighttime temperature variation
within the soil profile can be extreme.
Forest communities within Pringle Falls are representative of low- and mid-elevation regional
Pringle Falls Experimental Forest (Oregon) landscapes. Aspect, elevation, and past disturbance events
(especially fires, insects, and disease, and more recent timber harvesting) have created a mosaic of rich
biological diversity. Ponderosa pine is the dominant conifer through most of thPringle Falls. Shrub layers
include antelope bitterbrush, ceanothus, greenleaf manzanita, giant chinquapin, and bearberry. A fire
regime of low-intensity burns every 7 to 20 years, coupled with infrequent large and more intense fires, was
common prior to the advent of modern fire suppression.
Dense stands of lodgepole pine with antelope bitterbrush, Idaho fescue, western needlegrass, and
bearberry occur on flats and basin bottoms that are slow to drain in the spring and, because of topography, are
prone to frequent frosts that kill ponderosa pine seedlings. In the mixed-conifer forest type at higher
elevations, stands may contain ponderosa pine, grand fir, Shasta red fir, sugar pine, western white pine, whitebark
pine, and mountain hemlock.
Long-Term Data Bases
An annotated bibliography of publications resulting from research at Pringle Falls from 1930 to 1993 was
published in 1995 and is available from the PNW Station.
Research, Past and Present
Some of the earliest forestry research in central Oregon occurred within Pringle Falls. In 1936, a rating system
for determining the susceptibility of ponderosa pine trees to western pine beetle attack was based on a westwide
study and monitoring effort that included ponderosa pine stands in Pringle Falls. In 1950, stand structure and
periodic growth measurements resulting from a study in which suppressed ponderosa pine seedlings were released
from a lodgepole pine canopy were published. During the next several decades, research concentrated on
determining the competitive effect of shrubs growing with ponderosa pine; use of prescribed fire to control
competing shrubs; and the soil thermal properties, surface temperatures, and seedbed characteristics required
for lodgepole and ponderosa pine regeneration from natural seedfall. Also during this time, logging methods
that ensured the survival of existing seedlings and saplings were developed, thus reducing future
reforestation efforts and costs.
During the 1970s, permanent research plots were used to study
the response of ponderosa pine to fertilization, and the release
and subsequent growth of ponderosa and lodgepole pines and grand
fir at various tree densities. During this time, the frequency,
intensity, and spatial patterns of wildfire in old-growth ponderosa
pine stands were examined, and the genetic characteristics of ponderosa
pine were described. Work beginning in the 1980s and extending up
through the early 1990s emphasized the response of dwarf mistletoe-infected
pine to thinning, interactions between fire and dwarf mistletoe,
and development of stands in response to various silvicultural practices.
Much of the current research in Pringle Falls is designed to increase our understanding of the long-term processes
that regulate or influence the structure, composition, and pattern of forests. Additional work will emphasize human
interactions in the wildland-urban interface and how these interactions influence risk.
Major Research Accomplishments and Effects On Management
Much of the knowledge on which current eastside ponderosa pine silviculture is based was developed at Pringle Falls.
Collaborating researchers from the Deschutes National Forest and Oregon State University have worked at Pringle Falls.
At Pringle Falls, there are opportunities for the following types
of research: manipulative and nonmanipulative research in ponderosa
and lodgepole pine silviculture, entomology, pathology, fuel reduction
and fire effects, and natural disturbance regimes; social interactions
involving high-density recreational use within a wild and scenic
river corridor; and wildlife habitat values.
The Pringle Falls Experimental Forest and Research Natural Area is about an hour’s drive south of Bend,
Oregon, and are easily accessed from U.S. Highway 97. Overnight facilities within the PFEF are available for
small groups involved in on-site research or educational activities.
Lat. 43° 42' N, long. 121° 37' W
Pringle Falls Experimental Forest
USDA Forest Service
Pacific Northwest Research Station
La Grande Forestry and Range Sciences Laboratory
1401 Gekeler Lane
La Grande, OR 97850
1Information has been updated since original publication.