INTRODUCTION 



Arabis fecunda is a rosette-forming perennial in the mustard 

 family (Brassicaceae) . Endemic to southwestern Montana (Ravalli, 

 Silver Bow and Beaverhead counties) , this recently described 

 species (Rollins 1984) is currently known from a total of only 

 fourteen locations. Arabis fecunda populations are restricted to 

 light-colored calcareous soils derived from metamorphosed calc- 

 silicate parent materials (Presley 1971, Richards and Pardee 

 1925) . These sites are found along small to large drainages at 

 the edges of mountain uplifts (Pioneer, Sapphire, and Highland 

 mountains, Montana) , where parent materials have been exposed by 

 erosion. 



Livestock grazing and encroachment by knapweed (Centaurea 

 maculosa ) have been a suspected threat to populations of A. 

 fecunda (Lesica 1991, Lesica and Shelly 1988). These studies 

 hypothesized that the effects of grazing on A. fecunda were 

 indirect through disturbance of soil crusts, and subsequent loss 

 of plants. Long-term demographic studies have provided some 

 information on these hypotheses (Lesica 1985, 1991, Schassberger 

 1988) , but actual exclusion of grazers was not attempted. 

 Although the trampling associated with grazing may be detrimental 

 to populations, grazing may also benefit A. fecunda populations 

 via a reduction of competing vegetation. This report documents 

 the establishment of exclosures to study the effects of the 

 elimination of grazing by large herbivores on portions of A. 

 fecunda populations at two sites on the on Bureau of Land 

 Management lands, Butte District, Headwaters and Dillon resource 

 areas. First year data obtained from these sites are included 

 here. 



STUDY SITES 



The locations and geographic details for the two study 

 sites, in Beaverhead and Silver Bow counties, are as follows: 



Quartz Hill Gulch : From Dewey, Montana, travel west on 

 State Highway 43 ca . 0.33 miles, turning south on Quartz 

 Hill Gulch road (Beaverhead National Forest road # 187) . 

 Drive approximately one mile up road and park on east side 

 of road. Exclosure is on open steep hillside west of road 

 as marked in Figure 1, p. 3. Pins were driven into the 

 ground at the four corners of the covered exclosure and the 

 outside corners of the adjacent control plot. 



Township IS Range lOW Section 8, NW^SE^ 



Aspect: 95° 



Thompson's Corner : From Dewey, Montana, travel west on 

 State Highway 43 ca. 3.2 miles, turning north on the Jerry 



