70 



This pattern of being locally widespread in very low population numbers is shared with 

 Astragalus platytropis in the Big Hole Study Area, which is treated similarly. 



MANAGEMENT CONSIDERATIONS: Townsendia nuttaUii is a low-growing plant in an 

 exposed, sparsely-vegetated setting, and it completes its life cycle early in the growing season. 

 For these reasons, it is little-affected by livestock grazing and might respond positively to 

 grazing that reduces competition. Mining activity is a low-level tlireat to the species because it is 

 localized and the species is widely-dispersed in low densities. Invasion by exotic species is 

 minimal or absent in the study area but poses the greatest potential direct threat to the species. 

 Species which might invade and dominate in its habitat include Bromus tectorum and Centaurea 

 maculosa. Grazing, mining, and other activities can occasionally promote the spread of exotic 

 species, thus posing indirect management concerns. 



UPPER MADISON VALLEY STUDY AREA 



Sur\'eys in the Upper Madison Valley Study Area expanded on the previously available 

 information regarding two sensitive species. Astragalus terminalis and Stephajiomeria spinosa; 

 the largest concentration of occurrences and the largest population numbers known to the state 

 were documented. Wliile there are no immediate threats to these species in the Study Area, 

 knapweed is beginning to spread throughout the valley; in addition, subdivision of the rangeland 

 that represents their primary habitat is widespread outside of the BLM tracts. 



The Stephanomeria spinosa studied is a Great Basin species at the northeastern end of its range, 

 while the Astragalus terminalis is a regional endemic that spans an unusually wide range of 

 elevations in Montana at the northern end of its distribution. 



