XI. SUCCESSION IN EURASIA. 



The abstracts of the successional studies on European and other vegetation 

 in the present chapter are grouped more or less exactly into general regions 

 as follows: (1) Scandinavia (including Finland); (2) Britain; (3) Middle 

 Europe; (4) Russia and Asia; (5) Mediterranean region; (6) Tropics and Sub- 

 tropics. An arrangement into climaxes proved so difficult and uncertain that 

 it was necessarily relinquished. While it is quite possible to recognize a beech 

 cUmax, a spruce climax, tundra, steppe, and sclerophyll climaxes, etc., the 

 limits of these are so uncertain and the disturbance produced by subclimaxes 

 due to man so great that the delimitation and correlation of European climaxes 

 must be left for the future. It is only natural that the study of succession 

 should have been regularly circumscribed by political boundaries, with the 

 consequence that the co-ordination of the units and results of various investi- 

 gators is a task yet to be done. 



A number of the European studies of succession have been dealt with in the 

 general historical summary in Chapter II, and a larger number have been 

 grouped together in Chapter XIII. Still others, such as those of Hult, 

 Warming, Nilsson, etc., have been discussed at various places in the text. 



SCANDINAVIA. 



Gronlund (1884) has described the vegetation of cliffs, heaths, lava fields, 

 chasms, warm springs, and ponds of Iceland. He has traced the development 

 in particular on the lava fields, which were formed in 1729. These are often 

 still covered only with lichens, especially Gyrophora and Stereocaulon; in 

 other areas occur a few mosses, particularly Rhacomitrium lanuginosum. 

 Flowering plants secure a foothold only where the lava has weathered into 

 soil. 



Keilhack (1886) has listed and described briefly the colonies about the warm 

 springs in Iceland, viz, Trijolium repens, Potentilla anserina, EpHobium 

 palustre, Sagina nodosa and S. procumbens, Montia rivularis, Viola palustris, 

 Ranunculus acer and R. repens, Sedum villosum, lAmosella aqvMica, Veronica 

 beccdbunga, Plantago major, Potamogeton pusiUus, Juncus bufonius, and Heleo- 

 charis palustris. Many of these also occur as fossils in the deposits of siliceous 

 sinter. 



Skarman (1887) has traced in detail the invasion of sandy shores and sand- 

 bars in Sweden by Salix triandra and its replacement by other species: 



On sandy areas just raised above the water-level, S. triandra is commonly 

 dominant. In places annually flooded, it maintains itself in some degree, but 

 elsewhere it is replaced chiefly by Alnus incana, which grows very rapidly and 

 overshades the willows. Salix nigricans usually invades early, and commonly 

 with Alnus incana. The outcome of the competition between these two is 

 determined by the preponderance of individuals, since both require about the 

 same light intensity. Salix daphnoides, on the contrary, is able to persist in 

 competition with all of the above, owing to its taUer growth. 



Raunhiaer (1889) has described the formations of the North Friesian 

 Islands: 



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