The Blacks Mountain Experimental Forest was formally designated in 1934 as the Station's principal site for management studies in the interior ponderosa pine (Pinus ponderosa Dougl. ex Laws. var. ponderosa) type. Studies going back as far as 1910 had resulted in new theories of management, silviculture, and insect control. A primary objective of the Experimental Forest was to develop these theories into a system of management and to test, demonstrate, and improve the system through continuous operation of a timber tract on a commercial scale.
Blacks Mountain Experimental Forest (lat. 40°40' N., long. 121°10' W.) lies within portions of T. 33 N., R. 7 E. and T. 33 N. R 8 E., MDM., 64 road kilometers northwest of Susanville, Lassen County (See Map [pdf]). About half of the Forest lies in a gently rolling basin; the remainder extends up the moderate slopes of Blacks Mountain to the north and of Patterson and Cone Mountains to the east. Elevations range from 1700 to 2100 meters (5600 to 6900 feet). (See Map [pdf])
Access to within 8 kilometers (5 miles) of the Experimental Forest is available all-year via State Route 44. Access to the boundary and within the Forest is available during summer and fall via an intensive system of surfaced and unsurfaced roads. None of these roads is maintained in the winter, and many may be impassable when wet.
The climate is characterized by warm, dry summers and cold, wet winters. Annual precipitation, mostly snow, for the period 1935 to 1953 varied from 229 to 737 millimeters and averaged 457 millimeters. About 90 percent of the precipitation falls during October through May. Air temperatures during the year usually range from -9°C to 29°C. Frost may occur in any month. Relative humidity is usually low -- 10 to 20 percent on summer afternoons except during storms.
Most of the soils are between 1 and 3 m deep over basalt. Typic Argixerolls with mesic soil temperature regimes predominate at lower elevations. Andic Argixerolls with frigid soil temperature regimes predominate at higher elevations.
Interior Ponderosa Pine (SAF 237), which occupies 3715 hectares (9200 acres), is the only forest cover type on the Experimental Forest (Eyre 1980). Species composition varies within the type, however. White fir (Abies concolor var. lowiana [Gord.] Lemm.) and incense-cedar (Libocedrus decurrens Torr.), absent in stands within the lower portion of the basein, become increasingly abundant at higher elevations. The remaining 437 hectares (1000 acres) are poorly drained flats occupied by sagebrush and grass.
Long-Term Data Bases
In 1933 and 1934, the Blacks Mountain was completely inventoried on a 1-ha grid. Timber type maps and inventories were prepared by compartments and updated following harvests. Computerized stem maps for a 20-year period and inventories for a 50-year period are available on 8-ha parcels (48). An ecological unit inventory was completed in 1994.
Research, Past and Present
Before full scale operations began, the approximately 4200-hectare (10,400 acre) forest was subdivided into 100 compartments of about 40 hectares (100 acres) each. An intensive road system, the first in the West specifically designed for truck hauling, was laid out such that every compartment was bordered by a road. Compartments and roads have been continuously maintained.
Early timber harvests were primarily for insect control. An insect risk-rating system was developed at Blacks Mountain (Salman and Bongberg 1942). When it was demonstrated that the average cut of 35 cubic meters per hectare could be logged economically, and that the cutting reduced the annual rate of tree killing, sanitation-salvage was adopted widely. Duncan Dunning proposed the mosaic of small even-aged groups of trees (the prevailing stand structure at Blacks Mountain) rather than individual trees as the subject for management (Hallin 1954). This concept of "unit area control" was tested operationally during the 1950's. More recent cuttings have been designed to convert large areas of the forest to young-growth stands needed for future research. Today, the forest includes a wide range of stand structures and age classes from young plantations to old-growth stands in five uncut compartments designated as Research Natural Areas.
An ambitious study of stand growth and development after several intensities of timber harvesting was begun in 1938. Each year for 10 years, four to six 8-ha plots were installed to test cutting prescriptions ranging from a commercial clearcut, to various intensities of partial cutting or no harvest. This methods-of-cutting study (MOC) was abandoned in the mid-1960s when research became focused on even-age management, but was resurrected in 1990 when interest returned to uneven-age management. In 1992, the MOC compartments became the basis for a new long-term interdisciplinary study of how forest structural complexity affects the health and vigor of interior ponderosa pine ecosystems, the ecosystem's resilience to natural and human-caused disturbances, and how such ecosystems can be managed for sustained resource values. In 1995, Blacks Mountain was selected as part of the North American Long-Term Soil Productivity (LTSP) Network for 1 of 12 LTSP experiments in California.
In October 2002, the Cone Fire consumed 647 ha at Blacks Mountain. Subsequently, a study of fire salvage impact and wildfire behavior in managed stands was initiated. Burned areas received varying levels of salvage to test response of fuel conditions and soil compaction.
Major Research Accomplishments and Effects on Management
The insect risk-rating system discussed above was developed at Blacks Mountain to identify large, old ponderosa pines at risk of being killed by the western pine beetle. When early logging operations demonstrated that as little as 35 m3/ha could be logged economically and that cutting using the insect risk-rating system reduced the annual rate of tree killing, such sanitation/salvage operations were employed over a wide area. A system for classifying ponderosa pine trees as to vigor, developed at Blacks Mountain in 1936, continues to be used widely. The concept of "unit area control" was tested operationally during the 1950s. A 50-year record of stand development demonstrated and quantified the increase in stand density, the influx of white fir, and the increased mortality of large, old ponderosa pines found in interior ponderosa pine forests throughout the West in the absence of periodic wildfire.
Scientists and foresters from Humboldt State University, Oregon State University, Wildlife Conservation Society, and Lassen National Forest have collaborated on studies at Blacks Mountain.
Blacks Mountain contains typical stands of interior ponderosa pine with a variety of stand structures from young plantations though natural stands of poles to partially cut and uncut late seral stands. Collaborators are sought to explore the responses of vegetation, wildlife, insects and other ecosystem components to stand structure, grazing, and prescribed fire.
Housing and office space is available at the Lassen National Forest's Bogard Work Center, 19 km southeast of the forest. Gasoline and general merchandise can be obtained in the town of Susanville, 64 km southeast of Blacks Mountain.
Salman, K.A. and J.W. Bongberg. 1942. Logging high risk trees to control insects in the pine stands of northeastern California. Journal of Forestry 40(7):533-539.
Hallin, William E. 1954. Unit area control-its development and application. Misc. Paper 16. Berkeley, CA: Pacific Southwest Forest and Range Experiment Station, Forest Service, U.S. Department of Agriculture;
Eyre, F.H. ed. 1980. Forest cover types of the United States and Canada. Washington DC: Society of American Foresters; 148 p.
Contact Information 1
Blacks Mountain Experimental Forest
USDA Forest Service
Pacific Southwest Research Station
3644 Avtech Parkway
Redding, CA 96002
Tel: (530) 226-2530
The overview presented here was originally published in:
Adams, Mary Beth; Loughry, Linda; Plaugher, Linda, comps. 2004. Experimental Forests and Ranges of the USDA Forest Service. Gen. Tech. Rep. NE-321. Newtown Square, PA: U.S. Department of Agriculture, Forest Service, Northeastern Research Station. 178 p. GTR-NE-321 - 5.5 mb pdf
1Information has been updated since original publication.