Introduction 



An understanding of mountain grassland ecosystems requires knowledge of both the 

 dynamic interaction between plants and of the effects of environment and environmental 

 variation upon those plants. Climate and variations in weather are unquestionably 

 among the environmental factors that most affect mountain grasslands. 



Our knowledge of mountain weather is sketchy at best. The influence of mountain 

 topography on weather renders extrapolation of records from valley stations to mountain 

 slopes hazardous. The only reliable means of gathering such information is to locate 

 weather stations on mountain slopes, which has been done to only a limited extent in 

 various parts of the West. 



Some information on weather has been obtained in the course of relatively short 

 term ecological studies, most of which have been concerned with the subalpine and 

 alpine zones. For example, Klikoff (1965) obtained two summers of weather data from 

 a timberline basin (elevation, 12,000+ feet) in Yosemite National Park, Calif. Summer 

 weather data were also collected during ecological studies in the alpine areas (eleva- 

 tion, 11,000 feet) of Rocky Mountain National Park, Colo. (Holway and Ward 1964; 

 Salisbury et al. 1968), and in the Medicine Bow Mountains of southeastern Wyoming 

 (Bliss 1956; Scott and Billings 1964). Mountain weather data were recorded for two 

 summers at somewhat lower elevations (7,000 and 9,000 feet) by Patten (1963) during 

 an ecological study in the Madison Range of southwestern Montana. 



Relatively long term weather summaries have been published for a few high mountain 

 locations. These include year-round records maintained for 19 years at elevations of 

 10,500 feet and for 15 years at 12,470 feet in the UTiite Mountains of Calif. (Pace 

 et al.l968), and for 6 years at elevations ranging from 7,200 to 12,300 feet on the 

 Front Range near Boulder, Colo. (Marr et al . 1968). In addition, Judson (1965) has 

 published 15 years of winter and spring weather data for Berthoud Pass, Colo., which 

 has an elevation of 11,315 feet. 



No published data are available describing in detail climatic conditions and 

 weather variations within the intermediate elevation (7,000-9,000 feet) mountain grass- 

 land areas of southwestern Montana. Patten (1963) reported on weather from the same 

 general area, but his data were limited both in detail and duration. 



Ecological studies of mountain grasslands necessitated acquisition of such weather 

 information. Consequently, four stations were established to record weather data con- 

 sidered to be of ecological significance to mountain grasslands. Summaries of these 

 data are presented here for those specifically interested in the effects of climate and 

 weather variations on this vegetation type and for those interested in mountain weather 

 in general. 



