Ecology of the Cincinnati Region 
199 
noticed. All three are on high flood plains, only reached by exceptional 
floods, as that of March, 1913. 
It is probable that this type of forest arises late in the pond-swamp 
succession. At least the ponds of the flood plain occupy the only other 
similar positions. None of these show any tendency toward the develop¬ 
ment of a swamp forest, but this may be due to the artificial conditions 
which surround them. 
Little can be learned as to the probable trend of the succession from 
the depression forests themselves, for they are completely cleared of their 
undergrowth. A comparison of the three depressions shows that their 
forests are not in the same stage of development. The largest one (on the 
flood plain of the Ohio river at Melbourne, Ky.) is undissected by small 
ravines. Its trees are of different ages and range from several inches to 
a few feet in diameter, some of the pin oaks being exceptionally large. 
On the margin of the depression, and not far from the willows and syca¬ 
mores of the flood plain forest is a single beech tree. This gives the only 
clue as to the possible future of the depression forest of flood plains, if un¬ 
dissected—a mesophytic forest, probably similar to that which follows the 
depression forest of the upland. 
The other two depressions are broken by ravines. One, on the Ohio 
river flood plain at Finney, Ohio, is trenched by a deep gully, along 
which are a few ravine trees. The third depression, north of Lockland, 
is traversed by several shallow valleys along which are sycamores. As 
on the uplands, the conditions which produced the depression forest are 
being destroyed by dissection. 
The depression forests of uplands and flood plains are alike in that 
they contain the same kinds of trees, and their successions are proceed¬ 
ing in the same general course, either toward mesophytism by gradual 
filling, or toward xerophytism, by dissection. The depressions of the 
upland depend upon rainfall, ground-water and impervious soil for their 
supply of water. Those of the flood plain depend upon rainfall and 
ground-water during only a portion of the year, for at times they are 
filled by the river. The alluvial soil is light and porous, very different 
from the till and white clay of the uplands. Topographic situation is 
a big factor in the production of swamp forests in the flood plain de¬ 
pressions. 
Flood plain forest .—The flood plain forest is closely related, in its 
development, to the constructional phases of river activity. It exhibits 
a number of zones whose extent and degree of development are depen- 
