Ecology of the Cincinnati Region 
193 
channel at one side of an island is filled up during a flood, and the island 
becomes a part of the shore. And, vice versa, a projecting portion of the 
shore may be suddenly transformed into an island by the gouging out of 
a channel across it. All parts of an island formed in this way are of 
very nearly the same age. For this reason, the normal asymmetry of 
vegetation of river islands as noted by Cowles ( 1901 ), is not seen here. 
Fig. 48. The steep lower end of one of the residual islands of the Little Miami 
river; near Gravel Pit. 
Instead, the zonation of associations is radial. The number of zones is 
dependent on the height and size of the island; their width upon the 
steepness of the island’s shores. Fig. 48 shows the lower end of the 
island in the map (fig. 4/). In this case, the lower end of the island is 
steep, and resembles the eroding portion of depositional islands. The 
upper end of this same island has very gently sloping shores, occupied 
by the first two vegetation zones, both open associations. Tree zones 
occupy the higher parts of the island—zone III that part between the 15 
and 20 foot contours, and zone IV, the area above 20 feet (fgs. 47 and 
49, BB' and CC). 
