252 



Origin of Biomes and Succession 



Central Lowland 



Physiographic Provinces 



aA Allegheny Plateau 

 t,V Interior Low Plateau 

 ce Lake Section, 

 i4 Till Plains, 



Southern Boundary of Glaciation 



Watershed 



,.._.. Smoll area included in Northeastern 

 Evergreen-Deciduous Transition 

 Forest (Shreve); Remainder - 

 Deciduous Forest. 



T 



VIRGIN FOREST 

 1798- 1820 



Beech -Maple 



Ash -Elm-Oak-Linden 



White Oak 



Southeastern Complex 



Chestnut 



Fig. 110. Five combinations of dominant deciduous trees in Ohio. (After 

 Sears in Shelford.) 



that different species of trees form a coiitiniuini over the surface, 

 one combination gradually merging into the next (Fig. 112) (see 

 also Mcintosh, 1958). In Whittaker's examples the distances be- 

 tween diverse combinations are short because the area is moun- 

 tainous and contains extreme ecological types in close proximity. 

 If this same type of intergradation were stretched out over flatter 



