THE DEVELOPMENT OF COMMUNITIES 



313 



the Caricion curvulae, the climax community of the alpine areas of the 

 Central Alps {cf. Braun-Blanquet and Jenny., 1926, pp. 226-240). 



The simplest form of this succession due to soil formation and the 

 development of vegetation is graphically shown in Fig. 157. "^ The 

 whole course of development, including soil formation, is to be regarded 

 as irreversible. 



The evolution of the soil and the development of vegetation follow a 

 similar course in other mountain regions such as the Pyrenees, the 

 Tatras, and the Colorado Rockies. It may be noted that the layer of 

 humus accumulated in the climatic climax association of the Tatras 



-!5% 



2 n 23 55 lOQ, ZOO 



Soil development 



270 280 Years 



Fig. 158. — Humus accumulation and acidification of old dune soil at Southport, Eng- 

 land, in the course of 300 years. {After Salisbury.) 



and of the Alps is thicker than that of similar associations of the eastern 

 Pyrenees or of the Colorado Rockies. In the Pyrenees the alpine 

 climax is an association of Festuca supina and C. membranacea, which is 

 less acid than the Curvuletum of the Alps or the Trifidi-Distichetum of 

 the Tatras. In the Colorado Rockies the climax alpine stage is occu- 

 pied by the Elynetum bellardii which appears to hold a position more 

 comparable to the climax of the Pyrenees than to those of the Alps and 

 the Tatras. The reason for these differences appears to be the greater 

 evaporation and higher summer temperature (smaller N.S. quotient) 

 in the Pyrenees and in the Rockies. 



Humid Regions of Europe. — It may be inferred that the laws of 

 development of vegetation and soil established in the humid alpine 

 region apply also to the humid regions of central, western, and northern 

 Europe. In Sylene National Park (Norway) Christopherson (1925) 



1 A somewhat different series, also leading to the Caricion curvulae, is shown 

 in Table 36. 



