10 



These mats appeared to be the principal soil 

 stabilizer in these habitats. 



In Wyoming, A, shultziorum is almost always found 

 in calcareous habitats. Populations occur in 

 soils derived from the Triassic Thaynes limestone 

 and the Paleozoic Wells and Amsden Formations in 

 the Salt River Range. In the upper Spring Creek 

 drainage, A. shultziorum is occasionally found on 

 a fine red soil that may not be calcareous. In 

 the Teton Range, it occurs on several Paleozoic 

 limestones and dolomites, including the Darby, 

 Bighorn, Gallatin and Gros Ventre Formations. 

 Astragalus shultziorum is commonly found on 

 somewhat vegetated rocky soils. In the Salt River 

 Range, it is often a co-dominant on vegetated 

 talus or scree at the bases of slopes below 

 calcareous cliffs. In the Teton Range, 

 populations are especially well-developed on fine 

 soils with calcareous pebbles, apparently derived 

 from the Death Canyon member of the Cambrian Gros 

 Ventre Formation. At these locations it almost 

 always grows in open habitat, usually in subalpine 

 forb communities (Marriott 1990) . 



REGIONAL CLIMATE: The Sawtooth Range is commonly 

 referred to as the "Front Range" of north-central 

 Montana. It is generally dominated by dry, 

 continental weather conditions. Much of the 

 yearly precipitation falls as rain or wet snov/ in 

 May and June, with large convective storms 

 providing the mid- and late summer moisture. 

 Winters are cold, dry, and windy, with 

 precipitation occurring m6stly in the form of 

 snow. For the Sawtooth Range populations,' the 

 nearest long term climatological station is at 

 Gibson Dam (4,735 ft), located approximately 14 

 air miles south and approximately 3,300 feet lower 

 than the plant populations. The mean annual 

 temperature for the time period 1951-1980 was 

 41.7° F. The mean maximum temperature for July 

 was 77.9° F, while the mean minimum temperature 

 for January was 11.2° F. For every 1,000 feet in 

 elevation gain, there is an estimated 5° drop in 

 temperature. Thus, the averages given above are 

 likely to be 10-15° higher than the actual 

 temperatures that the plant populations 

 experience. Mean annual precipitation was 18.52 

 inches (U.S. Department of Commerce 1982). 



