INTRODUCTION 



The Pryor Mountain Desert region has a flora and vegetation 

 unique in Montana (Dorn 1973, Kratz 1988, Lesica et al. 1984). 

 The arid climate and unusual and varied soils provide desert-like 

 habitats that are otherwise unknown in Montana. Furthermore, 

 this region lies at the north end of the Bighorn Basin, a broad 

 trough that extends south to the Red Desert of southern Wyoming. 

 The Bighorn Basin has undoubtedly been a migrational pathway for 

 desert plants (Dorn 1978). For these reasons numerous species of 

 desert plants reach the northern limit of their range in the 

 Pryor Mountain Desert • (Lichvar et al. 1985). Many of these 

 species occur nov/here else in the state. Furthermore, many plant 

 communities common in the Great Basin deserts reach their 

 northern limit here (Kratz 1988) , and some community types m.ay be 

 endemic to the area. Peripheral populations of species and their 

 habitats are often important areas for genetic divergence and 

 speciation (Mayr 1963). In addition, monitoring peripheral 

 populations and communities can provide insight into incipient 

 changes throughout their main geographic range. As such, the 

 area makes an important contribution to the overall biological 

 diversity of the state and the region. 



Floristic and ecological studies have been conducted in the 

 area of the Pryor Mountains in the past. Dorn (1978) made plant 

 collections in the area and reported the occurrence of many 

 species with Great Basin Desert affinities. South (1980) 

 provided a general description of common vegetation types and 

 their relationship to landscape features. In the mid-1980 's 

 researchers at the University of Wyoming conducted a study of the 

 flora and vegetation of Bighorn Canyon National Recreation Area 

 (NRA) , a narrov; corridor along the Bighorn River on the east side 

 of the Pryor Mountains (Lichvar et al. 1985, Knight et al. 1987) . 

 Their studies contributed a great deal to our knowledge of the 

 area. Finally, Kratz (1988) described four "Great Basin-type" 

 communities from the area based on a few carefully selected 

 stands. These studies produced a comprehensive list of species 

 present in the area and provided general descriptions of many of 

 the plant communities. Unfortunately, the exact locations of the 

 peripheral, disjunct and endemic species on most of the public 

 land in the area remained unknown. Furtherr.ore, a formal plant 

 community classification compatible v/ith regional schemes v/as 

 still not available. Thus, land managers are not able to 

 determine which communities should receive priority for 

 conservation management. Finally, locations of these rare 

 communities on public lands is not known. A comprehensive 

 management plan for this unique area cannot be achieved without 

 this information. 



The purpose of cur study is to provide the USDI Bureau of 

 Land Management (3LI-I) with the information necessary to properly 

 manage public lands in the Pryor Mountain Desert Region to 



