THE TREE 11 



The form of the root system varies with different species 

 of trees. Some trees, hke most of the oaks, the hickory and 

 walnut, develop a tap root or single main root that grows 

 down deep into the soil. Such trees are naturally wind firm. 

 They are practically never uprooted. They will be broken off 

 above ground before they will be blown over. With many 

 other trees like the spruce and birch, the roots tend to spread 

 out laterally in the upper layers of the soil. Such trees not 

 having a firm hold on the ground are not windfirm. A third 

 form of root system is where several strong lateral roots 

 extend down obliquely deep into the soil like the maple and 

 beech. These are fairly windfirm trees. The degree of wind- 

 firmness varies in the same kind of tree according to the con- 

 ditions under which the tree is grown. Trees in the open are 

 rarely seen uprooted no matter what kind of a root system is 

 naturally developed. A tree is able to strengthen its root system 

 to withstand 'the wind. Where trees grow closely together in 

 the forest they rely on each other for protection. Each tree 

 helps to hold the others up by preventing the wind from blow- 

 ing the tree over too far. Strong root systems are not devel- 

 oped. If such trees are thinned out suddenly, many of the 

 trees being removed, so that those left are deprived of their 

 former support, they will be apt to be blown over easily. If 

 such trees are thinned out through a series of years, the support 

 given by neighboring trees being gradually removed, the trees 

 left will thicken and strengthen their root systems and become 

 more and more wind firm, until finally they will be able to 

 stand alone in the heaviest winds. 



A few trees will adapt their form of root system to the con- 

 ditions of the soil on which they grow. With a deep soil a 

 deeply penetrating root system is produced, while in more 

 shallow soil a more spreading root system is formed. This 

 is true of but few trees. In general it may be said that unless 

 the soil is deep enough for the development of the character- 

 istic form of root system, the growth of the tree will be slow 



