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PLANT SOCIOLOGY 



the advance of alpine plant communities into the wooded region below 

 is thereby favored (Fig. 138). 



Finally the steepness of slopes and their surrounding conditions also 

 affect the development of the climaxes of soil and vegetation. In the 

 mountains of the temperate zones the climatic soil climax, and with it 

 the climax vegetation, can mature upon calcareous rock only when a 



Fig. 138. — Path of an avalanche on Munt La Schera, 2,000 m. (Lower Engadine). 

 In place of the destroyed larch climax forest a creeping scrub enters owing to repeated 

 Bcouring by avalanches. (Photo by Braun-Blanquet and Heller.) 



certain equilibrium in the slope is reached, and the angle falls below 10 

 to 15 deg. On steeper slopes than this, with basic soils, acidification is 

 impossible because of continuous additions of calcareous rubble and 

 water and also because of reduced humus formation. The climax 

 vegetation of the alpine levels of the Central Alps, Caricion curvulae, is, 

 therefore limited, in limestone mountains, to flat and moderately 

 inclined slopes. 



