ASSOCIATED VEGETATION: Arabis fecunda generally 

 occurs in relatively sparse vegetation. At three 

 sites, bare soil varied from 40% to 80%, and basal 

 vegetation varied from 20% to 50% (Lesica and 

 Shelly 1994) . Many of the sites occur on steep 

 slopes with very sparse vegetation and periodic 

 natural erosion. In some cases these steep slopes 

 support cryptogamic soil crusts that have been 

 shown to be beneficial to survival of A^ fecunda 

 plants (Lesica and Shelly 1992). 



In Ravalli County, zonal vegetation at A_^ fecunda 

 sites is Artemisia tridentata - Festuca idahoensis - 

 Aqropyron spicatum steppe, sometimes with a sparse 

 overstory of Pinus ponderosa . In Beaverhead and 

 Silver Bow counties, associated vegetation is 

 Cercocarpus ledifolius , Juniperus scopulorum or 

 Pinus f lexilis woodland, very open Pseudotsuga 

 menziesii forest or sparse Aqropyron spicatum 

 grassland. Habitat descriptions and common 

 associated species for the 18 sites are presented 

 in Table 2 . 



PHYSIOGRAPHY: All known Arabis fecunda occur in 

 the Northern Rocky Mountains of southwest Montana. 

 Populations in the north part of the range are 

 found in the west foothills of the Sapphire Range 

 in the Willow Creek drainage, a tributary of the 

 Bitterroot River. In the southern portion of the 

 range A^ fecunda occurs in the foothills and 

 mountains at the north end of the East Pioneer 

 Range and the Highland Mountains in the lower Big 

 Hole River drainage. One population in the 

 Highland Mountains is just across the divide in 

 the drainage of the Jefferson River. 



TOPOGRAPHY: Arabis fecunda usually occurs on 

 moderate to steep slopes with a warm (SE, S, SW, 

 W) aspect. Most sites are in lower slope 

 positions, although populations do occur on mid 

 and upper slopes. Elevations range from 4,700 ft 

 to 7,800 ft; sites in Ravalli county are at or 

 below 5,000 ft, while populations in the southern 

 portion of the range are above 5,500 ft. 



SOIL RELATIONSHIPS: Arabis fecunda occurs only on 

 soils derived from calcareous sediments that have 

 been metamorphosed to some extent by contact with 

 granitic intrusions. Soils are generally sandy in 

 texture with low organic matter content and a 

 light albedo. Results of analysis of soil from 

 the Charleys Gulch site in Ravalli county are 



