1966 



Canadian Forestry Journal, December, 1918 



to the movement of the earth and due 

 to dilTereJices of temperatures over 

 large areas, are the causes of what we 

 may call the cosmic climates; and by 

 local modifications of these conditions 

 the local climates are produced. 



It stands to reason that our means 

 are too puny to attempt an influence 

 on the causes of the cosmic climate, 

 and even the local climate can be 

 influenced only in a limited way; 

 especially if a practical issue or 

 considerable degree of difference is 

 considered. 



Even if we have found, as we have, 

 that temperature and humidity con- 

 ditions in a dense and extensive for- 

 est are different from those of an 

 open field, it remains still an open 

 question of how and how far the forest 

 condition influences the open field 

 conditions and vice versa; and how 

 large the area affected or to be affect- 

 ed must be to produce an influence of 

 practical value. 



Influence of large forests 



We know without measuring that 

 by interposing the shade of a single 

 tree between us and the sun we have 

 influenced the temperature of the 

 air; by building a house around us 

 we influence our local climate. A 

 small plantation on the open prairie 

 breaks the velocity and modifies the 

 temperature of the air on the leeward 

 side, but on the windward side such 

 an influence would not be niotced. 



We realize that a forest cover may 

 produce certain air conditions, but 

 their communication to surrounding 

 country W'Ould depend on its location 

 wdth reference to the prevailing winds: 

 the forest located on the leeside will 

 therefore have different influences 

 than on the windw-ard, on the neigh- 

 boring field according to their loca- 

 tion. The whole exchange and 

 mutual modification of conditions, 

 and whether the one or other condi- 

 ion will prevail in a practicably 

 sensible degree will depend on the 

 size o area of the same. Not only 

 the size of the area under foresi, 

 but the character of the forest, its 

 density, its soil cover, its composition, 

 elevation and exposure, its age and 

 height will determine the degree of 

 its influence. We can. therefore, 

 not readily generalize from place to 

 place. 



All we can safely claim is that the 

 forest condition, due to its lower 

 temperature and greater relative hu- 

 midity, is favorable to precipitation 

 as against the open field with its 

 higher temperature and drier air, 

 which furnish less favorable condi- 

 tions for precipitation. Extensive 

 forest areas are as a rule favored by 

 large rainfall, but is an open question 

 whether the forest is the cause or the 

 result. 



We must doubt, however, whether 

 the small woodlot is a rainmaker. 

 B. E. Fernow. 



Hind Screen to Cost 20 Millions 



Our government, says Pearson's 

 Weekly of London, has a scheme in 

 hand to create a wind screen of trees 

 along the top of the cliffs of the expos- 

 ed western coast, at a cost of twenty 

 millions. This screen will not only 

 supply much wanted wood, but will 

 prevent the salt Atlantic gales sweep- 

 ing over and souring the land behind 

 it, so freeing millions of acres of 

 land for wheat and other cereal 

 cultivation. 



QUEBEC'S FORESTS. 



Quebec province possesses 130 mil- 

 lion acres of merchantable forests 

 of which about 48,000,000 acres are 

 included in the fire-protected terri- 

 tories of the St. Alaurice, Ottawa 

 River, Laurentian and Southern St. 

 Lawrence Associations. Another fifteen 

 million acres of Quebec's forests are 

 privately owned, about nine million 

 acres being in the seignories. 



