The study area consists of that portion of the Pryor Mountain Desert north of the 

 Wyoming border and below the Douglas fir zone on the south slope of the Pryor 

 Mountains (ca. 1980 m). Lowest elevations are ca. 1220 m (4000 ft) at thesouthwest end 

 of the study area. We did not conduct sur\'eys on Bighorn Canyon N.R.A. or on private 

 lands within the study area. 



The oldest formation outcropping in the study area is the Madison limestone 

 which forms the south slopes of the Pryor Mountains. On more level terrain south of the 

 mountain slopes, younger formations overlie the Madison limestone. These are Paleozoic 

 and late Mesozoic sediments, predominantly sandstones and shales. The red sandstones 

 and siltstones interbedded with thin lenses of gypsum of the Chugwater formation are 

 particularly conspicuous (Richards 1955). A geologic history of the area is provided by 

 Knight et al. (1987). 



Soils in the study area are entisols, mollisols and aridisols (Kratz 1988). In 

 general, soils in the northeast portion of the study area are sandy and often calcareous, 

 while those in the south and west portions have a higher clay content and are often 

 saline. Very sandy soils occur locally where they weather from sandstone outcrops. 

 Productivity of the vegetation is low due to the arid climate. As a result, soil 

 development is minimal and organic matter is low. Shallow soils formed over Chugwater 

 sandstone are particularly barren. 



Climate of the study area is semi-arid. Bridger, Montana, 16 km (10 miles) north 

 of the west end of the study area at 1100 m (3680 ft), receives an average of 323 mm 

 (12.7 in) annual precipitation, and mean daily temperatures for January and July are -5.8'' 

 C (21.5° F) and 21.4° C (70.5° F), respectively (NOAA 1982). Lovell, Wyoming, 16 km 

 (10 miles) south of the east end of the study area at 1160 m (3800 ft), receives an 

 average of 180 mm (7.1 in) precipitation annually. Daily temperatures averaged -4" C 

 (16.8° F) in January and 22.0" C (71.8° F) in July (Knight et al. 1987). Spring and early 

 summer rainfall accounts for two-thirds of the annual precipitation, the balance coming 

 as snow (Knight et al. 1987). 



METHODS 



We conducted our surveys on 20-24 May, 9-13 June, and 23-29 June 1991. In 

 1990, spring and early summer moisture was average or above average, resulting in a 

 generally good flowering year for most species (Dean Culwell, personal communication). 

 In 1991, there were heavy rains in April, May and June. This above-average 

 precipitation directly following a good year produced an exceptional flowering year for 

 most species. We believe that the.se conditions allowed us to make a good evaluation of 

 the abundance of species of interest. 



