47 



b. Regional macroclimate: The climatic 

 recording station nearest to the Tobacco 

 Valley sites is located at Fortine, at an 

 elevation of 2,951 feet, approximately 17 

 miles south of the sites. For the 30-year 

 period ending in 1980, mean July maximum 

 and mean January minimum temperatures were 

 82.2°Fand 11.5 F, respectively. Mean 

 annual precipitation was 17.25 inches. 

 Poison Kerr Dam, at an elevation of 2,931 

 feet, is approximately 23 mile south and 

 east of the sites near Niarada, and 

 approximately 12 miles south of the Wild 

 Horse Island site. For the 30-year period 

 ending in 1980, mean July maximum and mean 

 January minimum temperatures were 82.3°F 

 and 17.9°F, respectively. Mean annual 

 precipitation was 14.98 inches (U.S. 

 Department of Commerce, 1982) . 



c. Local microclimate: Silene spaldinqii 

 appears to occur on north- to east-facing 

 slopes and in swales, in areas where snow 

 deposition is likely. These sites may 



- hold moisture longer into the spring. 



2. Air and water quality requirements: Unknown. 



3. Physiographic province: Hunt (1974) places the 

 range of S. spaldinqii in Montana in the Rocky 

 Mountains of Montana and Canada Province, 

 within the Rocky Mountain System. 



4. Physiographic and topographic characteristics: 



In Montana, S. spaldinqii occurs on alluvial 

 or eolian soils. These soils were deposited by 

 Glacial Lake Missoula, which formed during the 

 advance of the Cordilleran ice sheet that 

 blocked several major drainages in northwest 

 Montana. Repeated breaking of the ice dam 

 caused numerous catastrophic floods (Alt and 

 Hyndman, 1986) . Depositional materials extend 

 across Idaho and into Washington and Oregon, 

 and are likely to underlie the S. spaldinqii 

 populations in these states as well. 



Populations often occur on moderate slopes in 

 swales and drainages. In Montana, the known 

 sites occur from 2,700-3,500 feet in elevation. 



