30 FARM FORESTRY 



well above neighboring crowns spreading out in the sunlight. 

 These are called dominant trees. Other crowns occupy the 

 lower portion of the canopy, overtopped and shaded by those 

 above. These are the suppressed trees. Still other crowns 

 occupy a position between these two. They have their crowns 

 open to the light but they are narrow and restricted, due to 

 crowding by the taller, dominant trees. These are called 

 intermediate trees. Where the canopy is thick it prevents 

 excessive evaporation from the soil and serves as a protection 

 to the under portions from the drying effects of the wind and 

 sun and from the extreme cold of winter. Forest trees will 

 not grow well together unless the canopy is intact, so that the 

 floor is shaded from the sunlight, bringing about and main- 

 taining forest conditions. It keeps the air and soil moist be- 

 neath the trees and prevents a heavy growth of grass, weeds 

 and berry bushes, that would rob the trees of moisture and 

 food. 



The Region of the Boles. — This comprises the space be- 

 tween the canopy and the undergrowth or forest floor. It 

 is occupied by the boles of the trees and is high or low 

 according to the distance the canopy is above the forest floor. 

 The air surrounding the boles has greater humidity than the 

 air outside the woodlot and is warmer in winter and cooler 

 in summer than the air in the open. 



The Undergrowth. — The undergrowth comprises seed- 

 lings, or reproduction as it is often called, of the trees in the 

 woodlot, together with bushes and shrubs. When the canopy 

 is thin or broken the undergrowth may have a beneficial effect 

 in protecting the forest floor from the sun and from the beat- 

 ing effects of rain and in preventing evaporation. But if the 

 undergrowth is too thick it may cause a reduction in the 

 growth of trees by absorbing large amounts of mineral food 

 and moisture from the soil. The future of the woodlot de- 

 pends on the young seedling trees in the undergrowth. Cut- 

 ting all the undergrowth, as is often done to open up the 



