INTRODUCTION 



The pinyon- juniper woodland vegetation type has historically provided forage (for 

 both livestock and big game), fenceposts, pine nuts, Christmas trees, firewood, charcoal, 

 mine props, and railroad ties. Pinyon- juniper woodlands are becoming increasingly 

 valued for their watershed, esthetic, and recreational values [Gifford and Busby 1975). 

 Planning for the conflicting multiple uses of these woodlands requires better ecolog- 

 ical understanding than is now available. Previous research in these woodlands has 

 been confined to small, selected areas. Lack of a broad perspective has limited under- 

 standing of how the results of previous studies relate to each other. Without know- 

 ledge of variation within the pinyon- juniper type, we cannot efficiently extrapolate 

 management successes to other areas or avoid actions that have produced known short- 

 comings at one or a few sites. 



A cooperative research program designed to provide a synecological stratification 

 of these woodlands was initiated in 1972 by the Department of Range Science at Utah 

 State University; the Renewable Resources Center at the University of Nevada, Reno; and 

 the Intermountain Forest and Range Experiment Station. The overall objective of this 

 program is to gain a broad synecological perspective of pinyon- juniper woodlands in the 

 Great Basin. The distribution of the woodland type, its flora, and variations in the 

 vegetal cover and tree dominants are discussed in this report. Subsequent reports will 

 deal with other aspects of floristic variation, successional patterns, subdivisions of 

 the pinyon -juniper type and their relations to environmental factors, and localized 

 applications of vegetation classification units to land use problems. 



PREVIOUS WORK 



The literature on pinyon- juniper woodlands has been itemized by West and others 

 (1973) , Aldon and Springfield (1973) , and Smith and Schuster (1975) . Various chapters 

 in the compilation edited by Gifford and Busby (1975) provide an excellent overview 

 of land use history and of current taxonomic, autecologic, and synecologic under- 

 standing of this ecosystem. Therefore most references to earlier research will be 

 deferred until our discussion. 



A consideration of the extent of pinyon- juniper woodland is, however, appropiate. 

 This woodland is thought to cover from 43 to 100 million acres (17 to 40 million ha) 

 in the southwestern United States. The vast difference in estimated acreage depends on 

 the definition of the pinyon- juniper vegetation type. The smaller figure is based on 

 Kiichler's (1964) map of the potential (climax or pristine) juniper-pinyon woodlands 

 centered in the Four Corners States plus Nevada. An estimate of 76 million acres 

 appears in Senate Document 199 (Clapp 1936). Allred (1964) gives the highest estimate. 

 The Clapp and Allred estimates include juniper that has invaded other areas since the 

 activities of white men altered the original vegetation. 



West and others (1975) estimate that about 30 million acres (12.5 million ha) of 

 these woodlands occur in the Basin and Range Physiographic Province. This amounts to 

 about 38 percent of the total area of pinyon- juniper dominated vegetation in the 

 United States. Most of this pinyon- j uniper is in the Great Basin portion of the Basin 

 and Range Province. Thus, both in terms of area and proportion of the total pinyon- 

 juniper woodland, the Great Basin has major amounts of this kind of vegetation. 



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