from Hamilton and Divide, the two closest recording stations to 

 the Ravalli County and Beaverhead County sites respectively. 

 Mean monthly deviation from the 30-year normal for temperature 

 and precipitation were calculated for the each year up to and 

 including the spring when demography data were collected (data 

 from National Oceanic and Atmospheric Administration) . Take 1991 

 for example, summer included June, July and August, 1990) ; fall 

 included September, October and November, 1990; winter included 

 December, 1990 and January and February, 1991; and spring 

 included March, April and May, 1991. Entries for each site and 

 each year were used in the analyses. These samples cannot be 

 considered independent even though responses of A^ f ecunda 

 populations were often very different in the same year (see 

 Results) . As a result, significance testing of these regressions 

 is not valid, and reporting probability values is not 

 appropriate. Nonetheless, these analyses provide useful insight 

 into environmental factors affecting demography. 



RESULTS 



Vegetation 



Mean canopy cover estimates for dominant vascular plant 

 species are presented in Table 1. Total basal vegetation cover 

 was generally similar at the four sites (Table 1) . Graminoids 

 were common at Lime Gulch, but forbs were more common at the 

 other three sites. Bare soil was more common at Charleys Gulch 

 and Lime Gulch, while rock was more abundant at Birch Creek and 

 Vipond Park. A marginally significant effect on bare soil was 

 attributable to site (ANOVA; F=4.5, P=0.09), and the amount of 

 bare soil at Birch Creek and Vipond Park compared together was 

 greater than at Charleys Gulch and Lime Gulch (P=0.03). 



Population Growth 



Density of Arabis fecunda at the two Pioneer Range 

 transects. Lime Gulch and Vipond Park, was 2-3 times higher than 

 Charleys Gulch or Birch Creek in the Sapphire Range. Over the 

 course of our study the number of A^ fecunda plants decreased by 

 ca. 10% at Charleys Gulch and by more than 40% at Birch Creek but 

 increased by 37% at Lime Gulch and 65% at Vipond Park (Fig. 1) . 

 Population growth varied among years at all sites (Fig. 2) . The 

 Charleys Gulch and Lime Gulch populations showed low to moderate 

 among-year variation and displayed similar patterns in growth 

 between 1990 and 1992. On the other hand, the Birch Creek and 

 Vipond Park populations displayed high variability in growth rate 

 and had similar responses in 1990 and 1991. Responses in growth 

 rate between Charleys Gulch-Lime Gulch and Birch Creek-Vipond 

 Park were opposite in sign in three of the five years (Fig. 2) . 



