Lesica and Shelly (1992) found that soil crusts 

 are beneficial to A^ fecunda survivorship at some 

 sites, and these crusts are often destroyed by 

 livestock. Livestock also adversely affect 

 survivorship by directly trampling plants, and 

 this effect can be locally severe (Lesica and 

 Shelly, pers. observation). However, many of the 

 largest populations are also the most heavily 

 grazed. It is possible that a small plant like A. 

 fecunda that is not eaten would benefit from 

 having larger neighbors grazed. After two years, 

 exclosure studies at two sites near the Big Hole 

 River have also yielded equivocal results. At one 

 site A^ fecunda density increased in the exclosure 

 compared to controls, while in the other A. 

 fecunda decreased. Lesica and Shelly (1994) found 

 that A^ fecunda populations can have different 

 life histories; some populations are more 

 dependent on adult survival for population growth. 

 These populations would tend to be more adversely 

 affected by livestock trampling. 



Over the long term, livestock grazing will 

 probably be detrimental to survival of A_^ fecunda 

 populations because, in addition to trampling 

 plants, livestock are also significant vectors for 

 exotic weed encroachment. This double negative 

 impact will probably outweigh increases in 

 recruitment at most sites. 



3. MINING: At this time there is only one A_^ fecunda 

 site that is near an active mine, and there have 

 been no adverse effects to date. Nonetheless, 

 many A^ fecunda populations are near mining claims 

 or inactive mines that could become active in the 

 event of improved extraction methods or increases 

 in the value of minerals. Consequently, mining 

 activity does pose a potential risk to A^ fecunda 

 populations . 



4. HERBICIDE APPLICATION: Many Ravalli County Arabis 

 fecunda sites are located in areas with severe 

 infestations of Centaurea maculosa , a state listed 

 noxious weed. Consequently, these populations may 

 be subject to weed control measures such as 

 herbicide application by government or private 

 agents. The effects of various herbicides on A. 

 fecunda are not known. 



II. ASSESSMENT AND MANAGEMENT RECOMMENDATIONS 



26 



