476 ECOLOGY AND WILD LIFE CONSERVATION 



The term biome has been applied to the formation or association of 

 plants and animals which cover a large area in which the climate and 

 other conditions are fairly uniform. All the organisms which live in a 

 biome are called the biota. In North America north of Mexico the two 

 main factors in the distribution of plants and animals are temperature 

 and rainfall. The following biomes are usually recognized : tundra, 

 northern coniferous forests, the deciduous forests, southern evergreen 

 forests, the great plains grasslands, deserts, western coniferous forests, 

 and the tropical biome, the latter occurring only in the southern half 

 of Florida. 



The Tundra Biome. In northern Canada and the arctic islands, con- 

 ditions are so frigid, the growing season is so short, the soils are usually 

 so thin, and the winds are so strong that no trees can survive there. 

 Typical plants are reindeer lichens, mosses, and fast growing annuals 

 which spring up and bloom for a few days each summer. The reindeer 

 lichen furnishes much of the food for arctic hares, the caribous, and 

 larval stages of many arctic butterflies and other insects, and so in- 

 directly for the arctic foxes and wolves that prey on them. Tundra 

 plants grow under rather similar conditions on the highest mountains 

 of New England and New York, and down the Rocky Mountains nearly 

 to the Mexican border. 



Northern Coniferous Biome. This has been called the spruce-moose 

 formation after the largest animal and the dominant tree. This biome is 

 characterized by cone trees of many species with needle-like foliage. 

 Only one, the larch, sheds its needles in the winter. This formation ex- 

 tends across southern Canada and then enters the northeastern states 

 and down the mountains as far as eastern Tennessee and western North 

 Carolina. Timber wolves formerly preyed on the moose, and deer are 

 fairly abundant. The ruffed grouse and the spruce grouse are typical 

 game birds. Glacial lakes are very numerous and are filled with cold- 

 water fish. 



Deciduous Biome. This biome covers most of the eastern states as 

 far west as the Ozarks of Missouri and Arkansas and as far south as the 

 Gulf States. Dominant trees in the northern part of the area are sugar 

 maple and beech, in the southern parts oaks and hickories are most 

 abundant with the graceful tulip poplar common in rich bottomlands. 

 The foothills of the southern Alleghenies have the greatest variety of 

 trees of any region in the world. As the forests have been cut, the wild 

 turkey has become scarce but the white-tailed deer has become increas- 

 ingly abundant at least in the northern half of the region. Bobcats and 

 foxes are the largest carnivores today ; black bears are still common in 

 the mountains. Tree-nesting birds are most abundant, but the bobwhite 



