River watershed. Populations occur at mid- 

 elevations (5000-6000 ft, (1525-1830 m) ) , on 

 slopes that range from 0-40 percent. Most of the 

 populations occur on toeslopes and along valley 

 bottoms. 



3. SOIL RELATIONSHIPS: In Montana, A. brevistvla has 

 been found on alluvial and colluvial limestone 

 substrates. Populations occur on soils derived 

 from Madison Limestone, the Monarch Formation 

 (brown & black granular limestone capped by- 

 shale) , and the Barker Formation (limestone and 

 micaceous shale, containing beds of limestone 

 conglomerate and quartzite at the base) (Weed 

 1899) . 



4. REGIONAL CLIMATE: The regional climate of central 

 Montana is characterized by warm summers and cold, 

 snowy winters. The precipitation peak in central 

 Montana is generally as rain or wet snow in May 

 and June (U.S. Department of Commerce 1982). 



The climatic station closest to the central 

 Montana sites is at Stanford (elevation 4308 ft. 

 (1315 m) ) , which is approximately 18 miles 

 northeast, and about 1500 feet (460 m) lower than 

 most of the sites in the Little Belt Mountains. 

 For the period 1951-1980 (U.S. Department of 

 Commerce 1982) , the January mean temperature was 

 20.5°F (2.6°C), the July mean temperature was 

 65.2°F (18.6°C), and the annual mean temperature 

 was 43.2°F (6.3°C). The mean annual precipitation 

 was 15.34 inches (38.4 cm), with May (3.01 inches) 

 (7.5 cm) and June (3.07 inches) (7.7 cm) being the 

 wettest months. 



F. POPULATION DEMOGRAPHY AND BIOLOGY 



1. PHENOLOGY: Plants begin flowering in Montana in 

 late May and early June, and often continue to 

 flower through early July. June of 1991 was a 

 very wet and cold month across most of the state, 

 including the Little Belt Mountains. Several 

 populations of A. brevistvla were at the height of 

 bloom on July 1, nearly two weeks later than the 

 previous year. Fruit and seed set usually occur 

 in July and August. 



2. POPULATION SIZE AND CONDITION: The following 

 population sizes are underestimated, since 

 flowering plants are usually the most visible and 

 are easily counted. It was not practical to try 



