THE LIFE HISTORY OF TREES IN THE WOODLOT 37 



has all the space it needs for the expansion of its crown and 

 roots. As the little seedlings gradually grow in height they 

 also spread their crowns by extending the side branches. It 

 is not many years until the ground becomes shaded. With 

 the coming together of the crowns the sapling stage usually 

 begins. 



(b) The Period of Rapid Height Growth. — Until the 

 crowns of the little trees come together the soil is exposed ' 

 to the sun and wind and to the beating and washing eiifect 

 of the rains, and is dry and hard and less fertile than if it 

 had been under cover. As a consequence the growth of the 

 trees is slow during the seedling stage. As soon as the ground 

 becomes shaded a forest floor begins to form. The soil be- 

 comes soft and light and because of the protection from the 

 sun it contains more moisture. The leaves from the trees 

 falling on the ground rot and begin the formation of humus, 

 which helps to enrich the soil. Grass and weeds which tend 

 to dry the soil disappear because of the reduced light. With 

 the formation of the forest floor and a bettering of the soil 

 conditions a change comes over the life of the stand, and the 

 young trees begin to grow rapidly in height. So we see that 

 the growing of trees together has a beneficial effect. Each 

 tree tends to help its neighbor by protecting it from the sun 

 and wind, and by helping to enrich the soil! 



Trees growing thickly together in the forest not only have 

 a beneficial effect on each other, they also exert a harmful 

 effect in that they tend to modify the natural form and de- 

 velopment of each other. 



When the crowns of the trees come together further ex- 

 pansion in a sidewise direction practically ceases and the 

 energy of growth becomes concentrated in the terminal buds 

 in the tops of the trees, where alone height growth takes place. 

 Each little tree now seems as though it were running a race 

 with its neighbors to secure the space and light above. The 

 contest is not an equal one. Some of the trees are naturally 



