16 FORESTRY 



veloped from small sizes, under the same conditions, an 

 have adjusted their root system to the moisture supplj 

 and their boles and crowns to the exposure to wind an 

 abundant light. The ground about such trees may be bake 

 hard by the wind and sun, or covered with a dense sod, bu 

 the tree will resist these drying influences since it has a] 

 ways had them to contend with, and its roots have sprea< 

 out and struck deep, insuring abundant moisture. At th 

 same time, the trunk at the base has swelled into a stron 

 buttress, and the crown lies low on a tapering bole, so tha 

 the form and strength of the stem are ideal for resistin 

 the sudden onslaught of a fierce wind. Competition wit' 

 other trees is eliminated, and the tree easily masters th 

 opposing forces of the elements. 



The Struggle for Moisture and Light and its Effect o: 

 the Form of Trees. — But in the forest, single trees gro^ 

 so closely together that there is a struggle between ther 

 for the necessities of life, light and moisture. Plant foo< 

 is taken up by means of water, always in solution, and th 

 amount of moisture present is of more importance in it 

 effects on tree growth than the richness of the soil in chem 

 jical food supplies. This struggle for light and moistur 

 Jgives the forest its distinctive form. Wherever there i 

 sufficient soil moisture to support a full stand of trees, th 

 competition is fiercest for light. But in many places th 

 moisture is very scant, and then the struggle becomes who! 

 ly one of root competition for water. The form of a fores 

 growing on dry soil is necessarily open. Trees are space< 

 at considerable intervals, and their crowns have room t< 

 develop. But investigations show that the stand is realh 

 as dense as the soil will support. Young seedlings whicl 

 may spring up, die out in a few years, because they ar< 

 unable to get moisture. The roots of the old trees, large: 

 and more vigorous than the seedling, and penetrating deep 

 er, suck up all the water, and the seedlings perish o: 

 drought. Such stands are true forests, although they maj 



