V. 



SETTING 



The four study areas selected were near the north end of the Gravelly Range in 

 southwestern Montana, approximately 12 miles southeast of Virginia City. The areas were 

 on gentle southwest and northeast exposures, two at an elevation of 7,100 feet and two 

 at 8,200 feet. The two lower areas were within 200 yards of each other, whereas the 

 higher areas, which were 5 miles away, were within 700 yards of each other. This 

 arrangement permitted determination of differences in development and production between 

 extreme exposures and between elevations. 



The soils, derived principally from limestone, were generally deeper at the upper 

 elevation and on northeast exposures. Annual precipitation usually ranged between 20 

 and 30 inches; about half fell from May through October. Precipitation during May and 

 June was usually heavy; it accounted for about one-fourth of the yearly total. 



All four areas were natural mountain grasslands dominated by Festuoa idahoensis. 

 Forbs were abundant. Many graminoid and forb species were common to all four areas, but 

 other species were restricted to specific sites. 



I collected data on plant development and herbage yields on all study sites for 5 

 consecutive years, 1964-1968. Each area was adjacent to a weather station established 

 to measure the climate on mountain grasslands. I recently described weather variations 

 over the same 5-year period (Mueggler 1971). 



