The Rate of Plant Migration 



By O. W Arrhenius 



IN THE SKERRIES (small islands) along the east coast of Sweden 

 the migration of plants plays a great role. Every year the 

 land rises from about 0.3 to 1.5 cm. New areas are constantly 

 wrested from the sea, and thus the water level in the soil changes 

 from year to year. Consequently the changes in the plant associa- 

 tions are very great, and the rate of migration is important in 

 the formation of the new associations. 



Usually these skerries are small — one acre or less. Their high- 

 est parts are rocks washed clean by the waves. Between these 

 rocks, in sheltered places, we find the soil apt for vegetation. 

 The most common profile of a place covered with vegetation in 

 the younger skerries is shown in figure i. 



Rocks 



Main direction 

 of the wind 



Fig. I. 



In order to examine these and related questions, some "bare 

 areas" were laid out in the early summer of 1920. The areas were 

 prepared as follows. In a typical plant association, a frame of 

 I square meter divided with iron strings into 100 small squares 

 was laid out. The plants were counted separately in each small 

 area. After this the humus layer was dug away. The upper part 

 of the mineral soil was then removed, put through a fine sieve, 



[I] 



