southwest-facing slopes; the Birch Creek site is 1430 m above sea 

 level, and the Charleys Gulch site is 1525 m. The two sites are 

 separated by ca. 10 km. At Hamilton, ca. 8 km southwest and 300 

 m lower, mean temperatures for July and January are 19.4° and - 

 3.8° C respectively, and mean annual precipitation is 32 cm. 

 Zonal vegetation surrounding the sites is foothills Aqropyron - 

 Festuca grasslands with scattered Pinus ponderosa Dougl. and 

 Pseudotsuqa menziesii (Mirb.) Franco. 



The Lime Gulch site occurs on moderate east- and west-facing 

 slopes above a small drainage on the east side of the Pioneer 

 Range at ca 1890 m. The Vipond Park site is on a moderate south- 

 facing slope at 2195 m at the north end of the Pioneer Range. 

 The two sites are separated from each other by ca . 32 km and from 

 the Ravalli County sites by ca . 130 km. For Divide, at 1675 m 

 and north and east of the two sites, mean temperatures for July 

 and January are 17.2° and -7.2° C respectively, and mean annual 

 precipitation is 31 cm. Zonal vegetation around Lime Gulch is 

 Juniperus / Cercocarpus woodland, while it is Artemis ia - Festuca - 

 Aqropvron steppe at Vipond Park. 



Soils at all sites are highly calcareous sandy loams derived 

 from outcrops of metamorphosed calc-silicates or limestone. 

 These soils have a tendency to slump on moderate to steep slopes. 

 Vegetation at these sites is sparse compared to surrounding 

 grasslands and woodlands. Cryptogamic soil crusts are common at 

 Birch Creek, Charleys Gulch and Lime Gulch (Lesica and Shelly 

 1992a) . 



Field methods 



In 1987 we established two permanent transects, one of 5 and 

 one of 12 contiguous 1-m^ plots at both Birch Creek and Charleys 

 Gulch. In 1989 we established two permanent transects of 12 

 contiguous l-m^ plots each at both Lime Gulch and Vipond Park. 

 We censused Arabis fecunda in 1987-91 at Birch Creek, in 1987- 

 1992 at Charleys Gulch, and 1989-92 at Lime Gulch and Vipond 

 Park. Sampling was conducted in late May at the Ravalli County 

 sites, mid-June at Lime Gulch and late June or early July at 

 Vipond Park. We chose these times because A_^ fecunda fruits are 

 mature or nearly so, but dispersal has not yet occurred. Plants 

 smaller than 0.5 cm in diameter were not recorded because they 

 could not be reliably distinguished from other species. We did 

 not distinguish between small- and large-size plants in 1987. 



Individual A^ fecunda plants were mapped and recorded using 

 the following size-life history classification system: 



Small (S) = single vegetative rosette < 2 cm in diameter 

 Juvenile (J) = single vegetative rosette > 2 cm in diameter 

 Multiple-rosette (M) = multiple vegetative rosettes 

 Reproductive (R) = plants producing 1-many inflorescences 



