Ecology of Animals 659 



stage is bare sand which is quickly invaded by the dune-binding grass. 

 As this grass holds the sand, beech plums and cottonwood are gradually 

 able to gain a foothold. These in turn are replaced by a mixed forest of 

 oaks, pines, and other species. Ultimately these are replaced by the cli- 



IF WE WERE TO SIT ON THE MIDDLE BEACH OF TODAY. . . 



AS THE YEARS GO BY, THE PREVAILING 

 WINDS WOULD PILE UP THE SAND, WHICH 

 WOULD BE CAPTURED BY GRASS 





AFTER A FEW THOUSAND YEARS 

 WE WOULD BE SURROUNDED BY 

 A BEECH AND MAPLE FOREST. 



SAND- WASHED UP OR 

 BLOWN IN. 



HUMUS -FROM 

 PLANTS AND 

 ANIMALS. 



Fig. 214. — Dune succession beginning with bare ground and culminating in a 

 forest. (From Readings in Ecology by R. Buchsbaum, copyright, 1937, by R. Buchs- 

 baum.) 



max forest. Although these stages are best characterized by the vege- 

 tation types, the animals likewise are characteristic of each associes and 

 the association. 



