NATURAL AREAS AND REGIONS 



249 



11. IDAHO 



BY R. A. MUTTKOWSKI 



I. GENERAL FEATURES AND ORIGINAL 

 BIOTA 



1. Physiographic regions 



Idaho might be compared to a chair, 

 the back and seat of which consist of 

 mountain ranges along the eastern 

 border. The area between the upper 

 and lower rung of the chair is occupied 

 by a great plateau, the Snake River 

 Plains. 



In the northern panhandle the moun- 

 tains are relatively low, chiefly of the 

 round top type. Toward the middle 

 of the state, the "seat of the chair," 

 the mountains grow very rugged and 

 precipitous. 



Throughout the state the bases of the 

 mountains lie in volcanic lava, upon 

 which are heaped the aeolian soils. 

 This is seen in the Snake River Plain 

 which is a built-up plain formed by out- 

 pouring sheets of tertiary lava inter- 

 bedded with accumulated sediments of 

 the tertiary Lake Payette, which two 

 processes of upbuilding were contem- 

 poraneous within the basin, out of which 

 this plain was formed. Through this 

 plain the Snake River eroded a canyon, 

 and finally drained this geologic lake. 

 Except for the extreme southeastern 

 part. 



2. Plant and animal communities 



All of the original types of communi- 

 ties are still available for study. Orig- 

 inally, two-fifths of Idaho comprised 

 the forests and mountains, two-fifths 

 the arid plains, and one-fifth the fer- 

 tile prairies. These proportions have 

 changed somewhat in regard to the 

 extent of the forests and the arid plains, 

 due to lumbering, grazing, irrigation 

 and reclamation. 



a. Forests. There are two types of 

 forests in Idaho, the western white pine 

 forests of the north (see page 210) ex- 

 tending from the Canadian boundary 

 to the Clearwater Preserve; and the 



western yellow pine forests in the central 

 and southern parts of the state. In 

 central and southern Idaho especially 

 the forests were interspersed with great 

 fertile prairies, called Camas Prairies, 

 by the early travellers, from their con- 

 tinuous Camas blue. 



In the montane forests of the northern 

 part of the state are found character- 

 istically the black bear (Ursus america- 

 nus group), grizzly bear, wolverine 

 (Gulo luscus), marten (Martes americana 

 group), fisher (Martes pennanti group), 

 weasel (Mustela sp.), marsh shrew 

 (Neosorex), masked shrew (Sorex per- 

 sonatus group), red-backed vole (Evoto- 

 mys), mountain lemming-vole (Phena- 

 comys orophilus], chipmunks (Eutamias 

 spp.), pine squirrel (Sciurus hudsonicus 

 richardsoni), flying squirrel (Glaucomys 

 sabrinus group), yellow-haired porcu- 

 pine (Erethizon epixanlhum group), 

 snowshoe hare (Lepus bairdii), moose 

 (alces americana group), and black- 

 tailed deer (Odocoileus}.L. R. D. 



Among the reptiles and amphibians 

 occurring in the Montane are the rubber- 

 snake (Charina bottae], a garter-snake 

 (Thamnophis), the western frog (Rana 

 pretiosa), the western toad (Bufo b. 

 boreas), and a salamander (Ambystoma 

 macrodactylum) . H. T. G. 



Idaho and Utah are filled with small 

 mountain ranges which are for the most 

 part isolated by stretches of arid ter- 

 ritory. Each range usually contains a 

 group of species peculiar to itself and 

 in many cases certain species are 

 apparently confined to some one of 

 these ranges. The genus Oreohelix here 

 reaches its greatest development in 

 species. While little study has been 

 given to the ecological features of dis- 

 tribution, a good idea of the distri- 

 bution of the genus Oreohelix among 

 the mountain ranges may be obtained 

 from the paper by Henderson and 

 Daniels, Proc. Acad. Nat. Sci. Phil, 

 1916, pp. 315-339. F. C. B. 



b. Yellow pine forests. (See page 209.) 



c. Alpine tundra. The central peaks 

 carry snow and ice fields the year round. 

 The vegetation is typically alpine. 



