Formation has the most xeric habitat locally, and is more or less 

 continuous from north to south across half of Montana. The closed 

 drainage topography in areas of the till plains further concentrates 

 salts at the watershed centers, so that a full spectrujn of freshwater 

 to brackish water conditions are represented in a prairie pothole 

 mosaic. 



Soils 



Soil classification and mapping has not been published for the 

 Sweetgrass Hills. Soil orders represented include mollisols, alfisols 

 and entisols, with udic and ustic moisture regimes, and a prevalent 

 frigid temperature regime, mapped in the general state soil map as a 

 combination of cryoborolls, cryoboralfs, and haploborolls (US Soil 

 Conservation Service 1978) . Large areas on the highest peaks, 

 including most forested habitat, have limited soil development and are 

 provisionally mapped as Rubbleland-Cowood complex. Soil development 

 is strongly influenced by local climate, topography, and parent 

 material. 



Climate 



Temperature and precipitation data is available from the nearest U.S. 

 Department of Commerce - National Oceanic and Atmospheric 

 Administration recording station in Chester (U.S. Department of 

 Commerce 1982) . The Chester area has a continental climate with low 

 precipitation, cold winters and hot summers. Mean annual 

 precipitation is an average 11.8-13.8" (30-35 mm; from Thompson and 

 Kuijt 1976) . Though there are no recording stations in the Sweetgrass 

 Hills, estimates have placed it at twice the level of annual 

 precipitation in Chester, i.e., 23.6-27.6" (60-70 mm) per year 

 (Thompson and Kuijt 1976) . The soils series of the Sweetgrass Hills 

 which are being mapped by the Soil Conservation Service are ones that 

 typically fall within a 15-19" zone (USDA in progress) , but this is a 

 very rough estimate. A computer-generated state annual precipitation 

 map shows the Sweetgrass Hills falling within a 14-40" range (Caprio 

 and Nielsen 1992) . 



Weather conditions of the 1993 growing season were somewhat warm and 

 dry in spring, with local reservoirs at low levels (McDermott pers. 

 commun.). Conditions became exceptionally cool and wet during the 

 remainder of the growing season, bringing local reservoir levels above 

 nbrmal. Over the course of one day, on June 12, a nearby ranch 

 recorded 8" of rainfall. On July 12, snow blanketed East and West 

 Butte summits. 



Flora 



A total of 403 species of vascular plants have been collected or 

 reported from the Sweetgrass Hills. The preliminary flora of the area 

 was dociamented by Thompson and Kuijt (1976), expanded in the first 

 sensitive species study (Western Technology and Engineering, Inc. 

 1989) and augmented in this study. This includes additions and at 

 least one deletion in the list of alpine and subalpine plants of the 

 Sweetgrass Hills (Western Technology and Engineering, Inc. 1989) . 



