3 



germination occurs following late summer and autumn rains, but a 

 second bout of germination may occur in the spring. Mortality of 

 seedlings and first year plants is high (Lesica and Shelly, 

 unpublished data) . Plants generally grow for at least one year 

 before blooming and then produce one or more inflorescences with 

 3-many flowers. Arabis fecunda is threatened by livestock 

 trampling and competition with the aggressive exotic, Centaurea 

 maculosa at the Ravalli County sites. It occurs in areas of 

 historic mining activity in Beaverhead and Silver Bow counties 

 (Schassberger 1988) . Arabis fecunda is a candidate for listing 

 as a threatened or endangered species by the U.S. Fish and 

 Wildlife Service (USDI, Fish & Wildlife Service 1990) and is 

 considered threatened in Montana (Lesica and Shelly 1991) . 



At many sites A^ fecunda often occurs in soil with a low 

 density of vascular plants but a relatively high cover of 

 cryptogamic soil crust. Soil crusts at our study sites are 

 similar to typical pinnacled crusts found in the steppe-deserts 

 of southern Utah and Arizona (J. Johansen, personal 

 communication). Common algae are Microcoleus vaginatus (Vauch.), 

 Nostoc commune Vauch. , JL. muscorum C.A. Ag. and N^ punctiforme 

 (Kuetz.) Hariot. Common lichens include Collema tenax (Sw. ) 

 Ach., Catapvrenium lachneum (Ach.) R. Sant. , Toninia 

 caeruleonigricans (Lightf.) Th. Fr. , Caloplaca tominii Savicz.C. 

 iunqermanniae (Vahl) Th.Fr. and Fulgensia bracteata (Hof fm. ) 

 Raanen. Patches of cryptogamic crust, typically 10-50 cm in 



