Pacific Northwest Research Station

Pringle Falls Experimental Forest and Research Natural Area

Introduction

Pringle 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 Oregon.

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.

Climate

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.

Soils

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.

Vegetation

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.

Collaborators

Collaborating researchers from the Deschutes National Forest and Oregon State University have worked at Pringle Falls.

Research Opportunities

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.

Facilities

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

Contact Information

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
Tel: (541) 962-6530
http://www.fs.fed.us/pnw/exforests/pringle-falls/index.shtml

¹Information has been updated since original publication.

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