USDA Forest Service

Pacific Southwest Research Station


Pacific Southwest Research Station
800 Buchanan Street
West Annex Building
Albany, CA 94710-0011

(510) 559-6300

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Ecology and Management of Western Forests Influenced by Mediterranean Climate

Blacks Mountain Experimental Forest

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.

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 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.


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). 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.

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.

Plant Communities

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.

Related Links

Interdisciplinary Research


Martin W. Ritchie

Literature Cited

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; 10 p. 

Eyre, F.H. ed. 1980. Forest cover types of the United States and Canada. Washington DC: Society of American Foresters; 148 p. 

Last Modified: Feb 16, 2006 01:44:30 PM