Sierra Ancha Experimental Forest

Description and History

The research mission of work on the Sierra Ancha Experimental Forest was to study the effects of grazed and ungrazed vegetation on water yields and to learn more about water cycle relationships within the diverse vegetation zones extending from the higher elevation mixed conifer forests to the semi-desert grass type (Gottfried et al. 1999, USDA Forest Service 1938). The area of the enlarged Experimental Forest is about 13,500 ac (USDA Forest Service 1953, Pase and Johnson 1968). The experimental forest is within the Tonto National Forest and located on the western slope of the Sierra Ancha Mountains about 10 direct miles from Roosevelt Dam. The Forest headquarters area at Parker Creek and the hydrologic installations were constructed by the Civilian Conservation Corps during the 1930s.

The Experimental Forest lies along the crest of the Sierra Ancha Mountain range and includes areas between 3,550 to 7,725 ft in elevation. Geology of the range is complex with sedimentary, metamorphic, and igneous rocks uplifted in a dome-like structure (Pase and Johnson 1968). Thick formations of Dripping Springs quartzite, dissected by deep canyons or with intrusions of diabase and basalt plugs and sills are common in much of the Forest. Troy sandstone occurs at higher elevations (Rich et al. 1961, Pase and Johnson 1968).

Precipitation averages about 33 inches at the higher elevations at Workman Creek, 25 inches at the intermediate elevations (4,800 to 6,000 ft) surrounding the headquarters, and 16 inches at the lower elevations near the Base Rock lysimeters (Pase and Johnson 1968). Pase and Johnson (1968) identified eight vegetation types including, from the high elevations to low: mixed conifer, mountain park, ponderosa pine, chaparral, oak woodland, desert grassland, desert shrub, and riparian. Fifty-seven percent of the Experimental Forest is covered by chaparral shrubs. The habitat relations of the vertebrate fauna have been described by Reynolds and Johnson (1964).

The Sierra Ancha Experimental Forest provides a unique research environment for conducting short- and long-range studies concerning basic hydrologic and ecological relationships in vegetation types ranging from mixed conifer forests to lower elevation desert shrub-grassland communities.

Cooperators

A number of organizations cooperated with the Rocky Mountain Station's research effort on the Sierra Ancha Experimental Forest. The Salt River Water Users' Association provided financial support for the treatments on Workman Creek. The Tonto National Forest assisted with implementation of these forest management treatments. Faculty and students from Arizona State University and the University of Arizona conducted collaborative experiments on Sierra Ancha. University-sponsored research has increased in recent years.