Chaparral Shrublands

Treatment and Results

In the early 20th century, watershed managers became concerned that erosion on the adjacent and headwater watersheds of the Salt River would move sediment into the newly constructed Roosevelt Reservoir and decrease its capacity. Measurements indicated that 101,000 ac-ft of coarse granitic sediments accumulated behind Roosevelt Dam between 1909 and 1925. The Summit Plots, located between Globe, Arizona and Lake Roosevelt, were established in 1925 by the USDA Forest Service 15 mi upstream from Roosevelt Dam to study the effects of vegetation recovery, mechanical stabilization, and cover changes on stormflow and sediment yields from the lower chaparral zone (Rich 1961).

Shortly after establishing the Summit Plots, the USDA Forest Service dedicated a research area known as the Parker Creek Experimental Forest in May 1932 (Gottfried et al. 1999, USDA Forest Service 1932). This experimental forest was enlarged and renamed the Sierra Ancha Experimental Forest in April 1938 (Fig. 3). Numerous hydrologic and ecological experiments that were conducted on the Sierra Ancha Experimental Forest.

Other studies began in the 1950s with the establishment of the Three Bar watersheds in chaparral vegetation on the west side of the Tonto Basin (Hibbert et al. 1974, DeBano et al.1999a). The initial research objective of the Southwestern Forest and Range Experiment Station (currently the Rocky Mountain Research Station) was to develop a program to study the interrelated influences of climate and soils, topography and geology, and the nature, condition, and use of watershed vegetation on streamflow, soil erosion, floods, and sedimentation.

Three Bar Watershed