BIOME AND BIOME-TYPE IN WORLD DISTRIBUTION 



593 



of mountains. The life zone concept, espe- 

 cially familiar in the faunal and floral litera- 

 ture of North America, is useful in the de- 

 scription of altitude zonation in mountains 

 (Fig. 19) in spite of a wholly erroneous 

 theoretical base (Daubenmire, 1938; vari- 

 ous state "biological surveys" of the Bu- 

 reau of Biological Survey in North Ameri- 

 can Fauna; Shelford, 1945; see also p. 

 114). Where the mountains are high 



American mountain goat, the ibexes of the 

 Eurasian mountains, the chamois, and the 

 pikas. The attendant carnivores are usually 

 entrants from lower zones like the puma 

 (Felis concolor) in the Rocky Mountains 

 and the Andes. The snow leopard of the 

 Himalaya appears to be the only large high- 

 altitude carnivore endemic to montane 

 tundra, commonlv referred to as the arc- 

 tic-alpine life zone in North America. 



Fig. 225. The rain forest biome: border of a clearing in the Ituri Forest of Nala, Belgian 

 Congo. (Photograph by Herbert Lang; courtesy of The American Museum of Natural 

 History. ) 



enough to maintain permanent snow, the 

 zone seasonally free from snow between 

 the summer snow line and timber line 

 may be closely representative of the tundra, 

 and, as in the Rocky Mountains, may pre- 

 sent essentially a peninsular southward ex- 

 tension of the animal life of the Tundra 

 Biome in a somewhat modified plant 

 matrix. The ptarmigan with its striking 

 color change from summer brown to winter 

 white, and the arctic butterflies of the genus 

 Parnassius, exhibit such a relation. It is to 

 be noted that the broken rock habitat, and 

 the otherwise modified montane environ- 

 ment exclude other characteristically arctic 

 forms and have associated with them strik- 

 ingly evolved mountain herbivores like the 



The taiga exhibits parallel southward ex- 

 tensions wherever north-south mountain 

 ranges in the northern hemisphere form a 

 connection with the latitudinal taiga biome. 

 As in the montane tundra, these southward 

 extensions tend to break up into outlying 

 islands and to be strongly modified in bi- 

 otic composition. Thus, the "Spruce-Moose" 

 biome of Shelford, when applied to the 

 Colorado coniferous zone, lacks the moose, 

 and when applied to the coniferous pine 

 forest of the Sierra Madre in western 

 Mexico, lacks the spruce as well. In gen- 

 eral, it seems best to base both definition 

 and nomenclature of the biomes upon gen- 

 eral vegetational type. Whereas the tun- 

 dra and taiga zones are evidently extended 



