FLOOD-PLAIN FOREST COMMUNITIES 203 



crane-fly larvae, and ground beetles. These had been swept into this 

 position by the current. Wood (21) says that the white-footed mice 

 and shrews climb the trees when the stream is in flood. As the number 

 of animals does not seem to be decreased after floods, the animals of the 

 lower strata of the flood-plain forest must be able to withstand sub- 

 mergence for days at a time. The fact that these floods come in spring 

 and winter when the animals are inactive doubtless assists in preserving 

 them because of the low ebb of their metabolic processes. 



e) Succession in the flood-plain forest. — As the stream works over its 

 flood-plain, it is constantly destroying the forest at some points and 

 depositing new materials upon which a new series develops at other 

 points. The depositing sides of the curves present the early forest 

 stages. Back of these and higher above the stream are the older stages. 

 Thus the horizontal series which we see when we pass from a depositing 

 bank across the various terraces is a duplication of the vertical series at 

 the oldest point or on the highest terrace. 



The higher and drier parts of the plain left by the lowering of the river 

 bed, and much of the flood-plain proper, are often well drained, rarely 

 flooded, and when thus drained pass rapidly into the oak-hickory type. 

 At such a stage the oak-hickory animal association is present and the 

 characteristic flood-plain animals have disappeared. 



/) Comparison with other moist forests. — There are a few species 

 common to the marsh and flood-plain forests. This is true of several 

 mammals and insects. One of the most characteristic of the insects is 

 the scorpion-fly. Many of the others belong particularly to the trees 

 common to the two, such as the ash, elm, basswood, etc. 



