268 



Origin of Biomes and Succession 



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



^TT^ 



^^^iL 



AS THE YEARS GO BY, THE PREVAILING 

 WINDS WOULD PILE UP THE SAND, 

 WHICH WOULD BE CAPTURED BY 



GRASS. 



.11/ 



zmmi!mzimyMm'////y///M/,:rK';S. 



AS THE HUMUS INCREASED WE WOULD 

 FIND OURSELVES SUCCESSIVELY AMONG 



THE COTTONWOODS. THE PINES, 



THE OAKS 



AFTER A FEW THOUSAND YEARS WE 

 WOULD BE SURROUNDED BY A BEECH 

 AND MAPLE FOREST . 



D 



SAND-AT THE TIME WE 

 FIRST SAT ON THE 

 MIDDLE BEACH. 



SAND-WASHED UP BY THE 

 WAVES AND BLOWN BY THE 

 WIND, SINCE WE FIRST 

 SAT ON THE BEACH. 



Wim\ HUMUS-ADDED BY 

 r>™^^ PLANTS & ANIMALS. 



Fig. 119, Diagram of community succession from open sand to beech-maple 

 climax in the dune region of northern Indiana. (From Alice, Emerson, Park, 

 Park, and Schmidt, Principles of Animal Ecology, W. B. Saunders Co., 1949. 

 Adapted from Buchsbaum.) 



a certain height and density, larch seedhngs become estabhshed, 

 new herbs and shrubs grow in their shade, and a new community 

 is formed, this time with trees as its dominants. All this time the 

 pond is filling up with decayed organic matter deriv^ed from pollen 

 and other material falling into the open water and dead moss 

 being pressed down from the top. When the pond is thus filled 



