STUDY AREA 



Custer National Forest - Ashland District is located on the most rugged breaks and ridges 

 between the Powder and Tongue River valleys, 5 miles east of Ashland and 42 miles west of 

 Broadus, in Rosebud and Powder River counties. Its outline has an irregular "J" shape which 

 curves inward along Otter Creek, extending about 41 miles north-south and up to 3 1 miles 

 east- west (Figure 1). 



The highly-dissected terrain drains in all directions, with the largest watercourses feeding into 

 the Tongue River. Rolling uplands are broken by complex ridge systems, with particularly 

 well-developed badlands topography at the southeast and west areas. 



The surface geology throughout is composed solely of the Tongue River Member of the Fort 

 Union Formation, which consists of shallow marine sedimentary deposits from the Cretaceous 

 and Tertiary Periods. Despite the uniform historical geology, the topography and stratigraphy 

 are decidedly heterogeneous. The highly-dissected terrain is carved by water erosion. The 

 horizontally-bedded outcrops include soft sandstones, silty sandstones, clayey shales and 

 lignite. Areas with burnt lignite have baked and oxidized adjacent beds to produce brittle, 

 erosion-resistant porcelainite (Warren 1959). 



The nearest long-term weather station is in Broadus (3030 ft.), with monitoring also 

 maintained at Ashland (as cited in Hansen and Hoffman 1987). Both have semi-arid 

 continental climates. The mean annual precipitation is 13 inches at Ashland and 14 inches at 

 Broadus. The mean annual temperature is 44.7° F., with a January mean of 18.2° F., and a 

 July mean of 71.2° F. The mean maximum temperature for July was 30.6° C (87.0° F), while 

 the mean minimum for January was -15.8 ° C (3.6° F). (U.S. Department of Commerce 

 1982). The year-round pattern of temperatures and precipitation at Ashland are depicted on 

 below. 



Topography of the District 

 intercepts precipitation and 

 influences weather patterns. This 

 climate is more distinguished by 

 its extremes rather than its means. 

 The broken terrain also divides 

 the landscape into an array of 

 microhabitats, each with its own 

 microclimate. 



Figure 2. Average monthly temperature 

 and precipitation at Ashland, MX. 

 From Hansen and Hoffman, 1988. 



