associations below the rank of life belt were considered as rela- 

 tively stable communities. 



The major plant-animal formations, or "biociations," in North 

 America have been classified and mapped by Kendeigh^24 jj^^q 

 tundra, alpine meadow, boreal forest-edge, boreal forest, western 

 forest, prairie, woodland, chaparral, basin sagebrush, desert 

 scrub, deciduous forest, deciduous forest-edge, and southern pine. 

 The biociations are further divided into plant-animal commu- 

 nities. In this hierarchical system, criteria of floristics, faunistics, 

 plant and animal sociology, and community dynamics are used. 



According to Knapp'^v ^^le chief formations or "zones" of 

 Europe (excluding the extreme southern, southeastern, and 

 western parts) are the evergreen-sclerophyllous-woody vegetation 

 near the Mediterranean; the Quercus pubescens formation in 

 southern Europe, extending from Spain to the Balkans; the 

 Quercus- Carpinus mixed forest, extending from England to east- 

 central Europe, north to southern Scandinavia, and southeast to 

 the Balkans; the mountain-beech forest reaching from north- 

 eastern Spain to the Carpathian and Balkan mountains; the 

 spruce forest at higher elevations in the mountains in central and 

 southeastern Europe, but most widespread in Fennoscandinavia 

 and northeastern Europe; the Empetrum "zone," containing open 

 woods and dwarf shrubs at high elevations with a distribution 

 similar to the preceding; and the arctic-alpine "zone" above the 

 tree-line in the mountains, and north to the tree-line in the 

 higher latitudes. 



Zonal classification of vegetation in restricted regions is useful. 

 As an example, the plant life of the Rocky Mountains has been 

 classified by Daubenmire^^ into six major zones: alpine tundra, 

 Engelmann spruce-alpine fir, Douglas fir, ponderosa pine, 

 juniper-pinyon, and oak-mountain mahogany. Another example 

 has been described on the east coast of Greenland,^^ where the 

 common zonation from the sea to the uplands comprises com- 

 munities of Festuca rubra nearest the sea, followed by those of 

 Cassiope tetragona, Vaccinium uliginosum, and Dryas integrifolium, and, 

 farthest from the sea, the lichen-moss assemblages. The complex 

 gradient from the sea to the uplands shows decreasing depth of 

 snow cover and increasing exposure to winds in the winter. 



Bases and Units • 187 



