PLANT ASSOCIATIONS OF WESTERN PENNSYLVANIA 



147 



The Floodplain Forest. The floodplain proper lies outside of 

 and above the transition zone. Its soil is alluvial and usually 

 bears a mesophytic forest. One would naturally expect this; 

 first, because of richness of soils of this type, and in the second 



Fig. 6. A pure stand of Tsuga Canadensis occurring as the first stage on the 

 slopes of the Allegheny Plateau. 



place because of the water supply which is generally favorable 

 for such a growth. 



The floodplain is subject to occasional submergence, but it is 

 only during exceptionally high stages that the upper portion of 

 this area is inundated. This occurs mostly at the time of heavy 



