Pacific Southwest Research Station

Experimental Forests, Ranges, and Watersheds

San Joaquin Experimental Range

Introduction

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A statement on the need for an experimental area in the San Joaquin Valley foothills was prepared in 1934. The initial purpose for the San Joaquin Experimental Range was to learn how to better manage these lands. San Joaquin lands were purchased in 1934 (1,387 ha), with additional purchases in 1936 (16 ha) and 1937 (372 ha). In 1938, another 64 ha were obtained under authority of the Weeks Forestry Act. Of these, 32 ha have been designated as a Research Natural Area. The San Joaquin is managed cooperatively by the Pacific Southwest Research Station and California State University's Agricultural Foundation, primarily for research and education.

Climate

The climate is Mediterranean, with about 486 mm of rain falling from October or November to April or May. Winters are cool and wet, with frequent frosts and monthly mean temperatures between 4 and 10 °C. Elevation ranges from 210 to 520 m above sea level, with most of the area between 300 and 457 m. Exposures are generally southwesterly. The area drains into a small tributary of the San Joaquin River. Summers are hot and dry, with maximum daily temperatures commonly exceeding 38 °C and monthly mean temperatures ranging from 24 to 27 °C.

Soils

Bedrock is mainly granitic. Soils on slopes are shallow, residual, and granitic and generally of the Ahwahnee series. Soils in swales are deeper and are alluvial and generally of the Visalia series. Slope and swale soils have a relatively low water-holding capacity. Granitic outcrops are common on slopes.

Vegetation

San Joaquin contains open woodland dominated by oaks (blue and interior live oaks) and digger pine with scattered shrubs and nearly continuous cover of herbaceous plants. Swales occur in low areas between rises. Dominant shrub species include ceanothus (both wedgeleaf ceanothus and chaparral whitehorn) and manzanita. Herbaceous plants are generally annuals including grasses (e.g., pine bluegrass soft chess, foxtail fescue), and various legumes. Perennials, primarily rushes, are found in the bottomlands. Native perennial bunchgrasses are uncommon and occur on north slopes.

Long-Term Data Bases

Data bases maintained at San Joaquin include long-term climate information, a list of all publications based on information acquired at the forest, spring bird counts begun in the mid-1980s, long-term acorn production censuses, and grazing intensity information.

Research, Past and Present

Nearly 400 publications have emerged from work at San Joaquin covering studies on energy flow, ecosystem modeling, nutrient flow, fire ecology, geology and soils, hydrology, weather and climate, grasses, woody plants, monitoring techniques, vertebrates (especially quail and passerine birds), invertebrates, livestock breeding/growth, livestock disease/nutrition, seeding, and sulfur fertilization.

Recent research addresses the following topics: geographical ecology of acorn production by California oaks; monitoring herbaceous production and utilization; effect of burning and overstory canopy on seasonal forage production and species composition; introduced annual clovers; beef sire evaluation; comparison of reproductive strategies of open- and cavity-nesting birds; methods for monitoring trends in bird populations in oak-pine woodlands; interspecific competition for nest sites between european starlings and native cavity-nesting bird species; foraging ecology of European starlings; effects of Africanized honey bees on pollination by other bees; and ammonia emissions from natural soils and vegetation.

Current educational activities include a variety of experiences for students with beef cow/calf production and management: in animal science, livestock and carcass evaluation, beef production, livestock and dairy evaluation, animal health, and artificial insemination and embryo transfer. Other educational activities include archaeology field classes, field day and leadership conferences to help to disseminate information generated at San Joaquin.

Major Research Accomplishments and Effects on Management

Significant contributions have been and are being made to the development of sustainable grazing systems in California's oak woodland savannas. The nearly 20-yearlong record of bird counts is an extraordinary resource for exploring the year-to-year variation of bird populations and diversity in oak woodland savannas.

Collaborators

Collaborating scientists from Fresno Agricultural Foundation, California State University-Fresno, University of California at Davis and at Berkeley, and Fresno City College engage in cooperative research at San Joaquin as do university extension, and cooperative extension groups from these same institutions.

Research Opportunities

Livestock are continuously present at San Joaquin and can be used in experiments to evaluate the relations among livestock, grazing effects, and plants and other animals. Ecosystem responses to prescribed fire in foothill oak woodlands can also be studied.

Facilities

Facilities include limited conference facilities, office space, barracks, and storage space available for approved research. San Joaquin Experimental Range is located in O'Neals, California, about 32 km north of Fresno.

Lat. 37°5´45´´ N, long. 119°43´45´´ W

Contact information