2) document selected groups of invertebrates 

 (especially tiger beetles); 



3) identify relationships between species distribu- 

 tions, stages of vegetation succession and 

 sandhills physiognomy; and 



4) provide information to assist managers in 

 maintaining the faunal diversity of this unique 

 area. 



Study Area 



Centennial Valley 



The Centennial Valley of Beaverhead County, 

 located about 80 km west of Yellowstone National 

 Park, is a relatively undeveloped area of Montana 

 and a biodiversity "hot spof (Povilitis and Mahr 

 1998). The valley is about 75% public and 25% 

 private ownership. Public lands include units 

 administered by the U. S. Fish and Wildlife 

 Service, U. S. Bureau of Land Management, U. 

 S. Forest Service, and State of Montana. Live- 

 stock grazing and livestock-related agriculture are 

 the principal land uses. 



The valley is an east- west trending basin about 60 

 km in length of 1 600 km^ within the "Southwest 

 Montana Intermontane Basin and Valleys" subsec- 

 tion of the Beaverhead Section (Nesser et al. 

 1997). The climate is cold and continental, with 

 warm dry summers and cold dry winters, and is 

 characterized by 22-50 cm of precipitation, of 

 which 10% falls as snow. The steep-sloped 

 Centennial Mountains form the valley's southem 

 boundary, with several summits between 2850 and 

 3087 meters in elevation. The Continental Divide 

 runs along the crest of the Centennial Mountains, 

 which form the north rim of the broad Snake River 

 basin to the south. The less rugged Gravelly and 

 Snowcrest ranges lie to the north of the valley, 

 each with elevations exceeding 3 1 80 m. This 

 broad, flat-bottomed basin was likely formed both 

 by^ erosion and by downfaulting which has oc- 

 curred here since the Miocene (Alden 1953). The 

 gradient of the valley floor is very slight, and there 



is little evidence of downcutting at the outflow of 

 the Red Rock Lakes (Banko 1 960). 



The valley supports over 700 plant species and at 

 least 20 major vegetation community types, 

 including the rare three-tip sagebrush-Idaho fescue 

 {Artemisia tripartita-Festuca idahoensis) type 

 that forms the climax vegetation of the Centennial 

 Sandhills (Lesica and Cooper 1 999). Over 26 1 

 bird species have been documented for the valley, 

 including the Trumpeter Swan (Cygnus buccina- 

 tor), which Red Rock Lakes National Wildlife 

 Refuge was established to protect. The valley also 

 hosts one of the two remaining native populations 

 of Montana Arctic Grayling (772ywo//M5 arcticus 

 montanus), and one of three known native 

 populations of Lake Trout {Salvelinus 

 namaycush). In addition, the eastern portion of 

 the valley offers a movement corridor and year- 

 round habitat for larger carnivores such as Lynx 

 {Felis lynx). Wolverine {Gulo gulo). Gray Wolf 

 {Canis lupus), and Grizzly Bear ( Ursus actos 

 horribilis). 



Centennial Sandhills 



The Centennial Sandhills, which lie in the northeast 

 comer of the Centennial Valley, are a unique 

 feature of the Greater Yellowstone Ecosystem. 

 They form a band approximately 2-3 km wide and 

 14 km long (between 44°40'N, 1 1 1 °42' Wand 

 44°42'N, 1 1 1°49'W) and cover about 3200 ha in 

 1 8-20 legal sections north of Lower and Upper 

 Red Rock lakes. The sandhills consist of small 

 and generally stabilized dunes created by sands 

 deposited probably during the late Pleistocene. 

 They are in various stages of activity, with the most 

 active and tallest lying north of Lower Red Rock 

 Lake (in Tl 3S R2W) and the lower and most 

 stable dunes present in the eastern portion of the 

 sandhills (in T 1 3 S R 1 W), east of Tepee Creek 

 (see Figure 1). Average elevation of the sandhills 

 is about 2030 m. 



The Sandhill vegetation is a mixture of succes- 

 sional types (Lesica and Cooper 1999) dominated 

 by shrubs (big sagebrush, ^rtemw/o tridentata; 



