INTRODUCTION 



In order to adequately protect populations of an organism, 

 it is necessary to understand its life history and population 

 dynamics (Massey and Whitson 1980; Sutter 1986; Palmer 1987). In 

 addition, many rare species are threatened by interactions with 

 non-native species that have been introduced into their habitat 

 (Drake 1988) . It is important to understand the nature of these 

 interactions in order to protect populations of rare species from 

 extinction. 



Arabis f ecunda Rollins (Sapphire rockcress) is a rosette- 

 forming perennial in the mustard family (Brassicaceae) . This 

 recently described species (Rollins 1984) is endemic to highly 

 calcareous, azonal soils in the foothills of the Sapphire and 

 Pioneer mountains in Ravalli, Beaverhead and Silver Bow counties, 

 Montana (Lesica 1985; Schassberger 1988). Arabis f ecunda occurs 

 on eroding slopes with low vascular plant density but a 

 relatively high cover of cryptogamic soil crust. Populations of 

 A. f ecunda are thought to be threatened by livestock grazing and 

 encroachment by Centaurea maculosa Lam. (spotted knapweed) , an 

 aggressive exotic weed (Lesica 1985; Schassberger 1988). 



This paper is a progress report on three studies being 

 conducted on populations of A. fecunda in Ravalli County. The 

 studies and their purposes are: 



1. Long-term monitoring of A. fecunda populations in order 

 to determine important life history attributes and 

 trends in overall recruitment and mortality. 



2. Spotted knapweed removal study, in order to determine 

 the effects of knapweed competition on the performance 

 of A. fecunda . 



3. Soil crust ecology study, in order to assess the 

 importance of soil crust to the establishment and 

 survival of A. fecunda plants. 



METHODS 



Study Areas 



Studies were conducted at two Arabis fecunda sites in 

 Ravalli County, Montana: Charleys Gulch and Birch Creek. The 

 Charleys Gulch site is on a steep, eroding, southwest-facing 

 slope along the drainage at an elevation of ca. 1524 m. 

 (5000 ft.) (T6N R19W S29, NW1/4). The Birch Creek site is on a 

 steep, eroding, southeast-facing slope above the creek at an 

 elevation of ca . 1433 m. (4700 ft). (T7N R19W S16, NW1/4). 

 Complete descriptions of the study sites can be found in Lesica 

 (1985) and Schassberger (1988). 



