THE DEVELOPMENT OF COMMUNITIES 323 



remain unchanged for a long time and maintain their social individual- 

 ity may be called permanent communities. 



The coating of blue-green algae on a limestone-rock surface, the 

 carpet of creeping willows of alpine snow land, the grassy woods near 

 the ground water along large rivers all are permanent communities. 

 They are distinguished from climax communities in not being limited 

 by climate and by possessing the potentiality of further development 

 when certain limiting factors are removed. Climax communities 

 can change only when there has been a change of climate. 



Climax Complex. Climax Area (Gehiet). — All seres in a natural 

 climatically uniform area must in the course of time, as the soil matures, 

 lead to the climatic terminal community. Obviously, this terminal 

 community will not be reached at the same time over the entire area; 

 and erosion and orogenic agencies will constantly make new rifts in the 

 mature plant covering. All long-cultivated regions, whose vegeta- 

 tion has been transformed according to human needs, show the terminal 

 community only in fragmentary remnants. Reconstruction of the 

 natural terminal community and its territorial delimitation are thus 

 made very difficult. For this reason not one climax community in 

 Europe has been exactly delimited. The principal climax communities 

 in French northern Africa have been mapped by Maire (1926), and the 

 great chmax communities of the United States are given on Shantz's 

 vegetation map in the "Atlas of American Agriculture." While 

 rather too general, Shantz's map is valuable as a preliminary sketch of 

 the natural vegetation of a large territory. 



The culmination of all the seres that lead to one definite climatic 

 terminal community is called the climax complex. The territory 

 covered by a climax complex is the climax area. It covers the surface 

 on which the climax community is theoretically possible. The 

 boundaries of the climax area are, however, rarely well defined. In 

 mountainous regions their course is irregular and follows the folds 

 of the valley walls. Outliers of foreign climax regions push deeply into 

 neighboring climax areas. The number of climax areas in central 

 Europe is small. They are most clearly distinguished and most 

 undisturbed in the Alps. 



Liidi (1921) distinguished in the Lauterbrunnen valley (Bernese 

 Alps) six chmax areas, corresponding to as many altitudinal 

 belts: 



1. The Fagetum silvaticae, up to 1,200 m. 



2. The Piceetum excelsae, 1,200 to 1,900 m. 



3. The Rhodoretum ferruginei, 1,900 to 2,100 m. 



4. The Nardetum, 2,100 to 2,300 m. 



