IMPROVEMENT THINNING. 



III. PRACTICE or THINNING. 



W7ten and How Often to Thin. 



Of course the conditions which exist in most parts of this 

 country do not permit of thinning as often as in some parts 

 of Europe. Our market conditions are different, and we 

 must be satisfied with a less intensive cultivation of our 

 forests. A safe rule to follow is to thin a young stand as 

 soon as the material to be removed has reached such a size 

 that its sale will pay for its removal, and as often thereafter 

 as the material to be removed has accumulated in sufficient 

 quantities to pay for its removal. If this rule is followed, 

 the improvement is a net. gain. If the rate of growth of our 

 native trees and their response to treatment were better 

 known, and if our forests were better protected from fire, 

 perhaps we could afford to thin a little before the material to 

 be removed would pay for its removal. We could thin at a 

 slight expense, and know whether the investment would be 

 profitable. But in the existing circumstances it is far better 

 to keep within the safety limit embodied in the rule just- 

 given. 



In practice this would mean a moderate thinning when a 

 stand is about thirty years of age, with a repetition every 

 ten or fifteen years thereafter. The trees in some stands 

 have not reached such a size in thirty years as to insure that 

 those to be removed will pay for the work ; while under 

 more favorable circumstances thinnings may be undertaken 



at an earlier age than that mentioned. 



i 



To What Extent to Thin. 



The extent to which a closed stand may be opened de- 

 pends on several circumstances. The kind or kinds of trees 

 that compose the stand, the nature of the soil, the character 

 of the undergrowth, and the purpose for which the timber 

 is to be grown, all play a part in determining the degree 

 of thinning. This is one of many matters in forestry that 

 cannot be reduced to a rule. 



The classes into which the trees in a closed stand gradu- 



