COMMUNITY SUCCESSION AND DE\^LOPMENT 



569 



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



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 BLO'.'/N BY THE 

 WIND, SINCE WE FIRST 

 SAT ON THE BEACH. 



HUMUS -ADDED BY 

 PLANTS & ANIMALS. 



Fig. 206. Diagram of succession (physiographic influences) and development (biotic in- 

 fluences) operating through time in the forest-on-sand sere in the dunes of northern Indiana. 

 (After Buchsbaum. ) 



Fig. 207. Succession and development in the microsere of cattle dung. Periods during which 

 predominant maggots were present in early stage droppings. ( After Mohr. ) 



