CHAPTER rV 

 SWAMP TYPE 



General Conditions. — This type is a comparatively unim- 

 portant one which occurs scattered here and there among the 

 three preceding t3rpes. It is all north of Mason and Dixon's 

 line and east of the Great Plains. In other words it is confined 

 to the glaciated regions. In fact the low lying sites in which it 

 occurs are in many cases directly due to glaciation. Beaver 

 dams are also a cause for the poor drainage which leads to the 

 occurrence of this type. On account of the small extent and 

 localized occurrence of this type it is impossible to give its occur- 

 rence by states and counties. It is only possible to say in general 

 terms where it may occur. 



The climate of the type varies, of course, with the altitude and 

 latitude but in general it may be said that the growing season is 

 shorter than on the surrounding upland because of the poor air 

 drainage. Swamps are more subject to late and early frosts for 

 this reason. While the precipitation is the same as that of the 

 surrounding country the available moisture is greater because of 

 the slow runoff and retarded evaporation. In fact there is too 

 much water in the soil for rapid plant growth. 



The height at which water stands has the same effect on root 

 development that a layer of hard pan would have. The roots 

 cannot reach down but must spread out. Furthermore, a fre- 

 quent cause of swampy conditions is an impervious soil whether 

 it be hard pan or clay. Consequently the soil conditions may 

 safely be said to be very poor for tree growth. Because the 

 roots cannot go down, the tree cannot grow tall and diameter 

 growth is minimized by the short growing seasons. 



The species which can endure such untoward conditions are 

 comparatively few. They must be shallow rooted and frost hardy. 

 Arbor vitae, southern white cedar, tamarack, spruce, balsam, 

 and red maple are the commonest. Usually they occur in more 



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