Test of RPA Production 

 Coefficients and Local 

 Assumptions for the 

 Pinyon-Juniper Ecosystem 

 in Central Utah 



Warren P. Clary 



INTRODUCTION 



The 1970 study "The Nation's Range Resources — 

 Forest-Range Environmental Study" evaluated forests 

 and rangelands in the 48 adjacent United States to deter- 

 mine the current and potential future production of ani- 

 mal unit months (AUM's) of grazing and for associated 

 products and benefits (Forest-Range Task Force 1972). 

 The information was used to construct alternate sets of 

 management goals for range livestock production and to 

 evaluate costs. In response to the study the Chief of the 

 Forest Service, U.S. Department of Agriculture, began the 

 Accelerated Range Program in 1973. This program in- 

 cluded a system of large-scale evaluation areas originally 

 conceived to test assumptions of the Forest-Range Task 

 Force and were to be a basis to make appropriate adjust- 

 ments in the Accelerated Range Program (Sanderson and 

 others 1988). These evaluation areas also were to serve 

 as a basis to test rangeland management production and 

 cost assumptions developed in response to the Forest and 

 Rangeland Renewable Resources Planning Act of 1974 

 (RPA). A secondary purpose was to provide local demon- 

 strations of range improvement practices. 



Evaluation areas were established in the Northwest, 

 the South, and in central Utah of the Intermountain 

 Region. The area in Utah, termed the "Oak Creek Moun- 

 tain Range Evaluation Area," was established in 1978 to 

 provide information on overall effectiveness of range man- 

 agement practices within the pinyon-juniper [Pinus 

 edulis, P. monophylla, Juniperus osteosperma) ecosystem. 

 The project emphasized the necessity of and benefits fi-om 

 coordinated planning and action between Federal, State, 

 and local agencies, as well as private landowners. Despite 

 disruptions caused by two large wildfires, thousands of 

 acres of revegetation work was completed (Pope and 

 Wagstaff 1987). 



The basic revegetation effort on the Oak Creek area, 

 excluding fire rehabilitation, was the conversion of spe- 

 cific areas of pinyon-juniper woodland to grass-dominated 

 plant communities to improve forage supplies. The objec- 

 tive of this study was to provide a field test of the specific 

 local and RPA assumptions of herbage and shrub produc- 

 tion in the pinyon-juniper ecosystem. 



STUDY AREA 



The Oak Creek Mountain Range Evaluation Area en- 

 compasses 316,000 acres about 15 miles north of 

 Fillmore, UT. The topography is highly variable ranging 

 from desert-shrub flats at the 4,800-foot elevation 

 through rolling foothills and benches to steep rocky peaks 

 that exceed 9,700 feet. The pinyon-juniper zone begins at 

 5,200 to 5,600 feet elevation with an upper limit of about 

 8,000 feet on south exposures and up to about 6,000 feet 

 on north exposures. The sagebrush zone is intermingled 

 with the pinyon-juniper zone. Vasey big sagebrush 

 {Artemisia tridentata ssp. vaseyana is most abundant 

 (Goodrich 1984). 



The climate is typical for the Great Basin, with cold, 

 moist winters and warm, dry summers. The average 

 long-term precipitation at the Oak City weather station 

 near the lower edge of the pinyon-juniper zone is 12.06 

 inches. Average precipitation of most of the pinyon- 

 juniper area included in this study is approximately 13 to 

 15 inches annually (U.S. Department of Agriculture-U.S. 

 Department of the Interior 1981). Precipitation at the 

 Oak City weather station shows rainfall was 119 to 159 

 percent of normal in the years of measurement (table 1). 



Specific study sites at Oak Creek included new treat- 

 ments and areas that had been treated in earlier years. 

 Data were obtained from four field situations: Church 

 Hills chaining of 1980, Clay Springs chaining of 1978, 

 Eight-Mile chaining of 1977, and Eight-Mile cabling of 

 1955. The Church Hills chaining consisted of six study 

 areas of 80 to 200 acres each; three were chained and 

 three were left as untreated controls. Ten transects of 

 10 plots each were established per area. The plots were 

 circular, 9.6 ft^ in area, and located 66 feet apart on the 

 transects. Weight estimates were made on the plots for 

 each grass, forb, and shrub species. Two additional plots 

 per transect were estimated then clipped, ovendried, and 

 weighed to determine correction factors for conversion to 

 dry weight. Twelve transects were located in the Clay 

 Springs chaining before treatment with the intent that 

 three would be in untreated areas. However, after the 

 planned treatment and an unplanned wildfire, one 

 transect could not be relocated and no transect remained 



1 



