IMPROVEMENT OF THE FOREST 203 



3. Tolerance of the species. 



4. Danger from windfall. 



5. Site. 



Purpose of Management, — The character of the 

 product depends on the density of the stand. If the aim 

 is to secure rapid growth in diameter, the stand must he 

 opened sufficiently to permit the development of a full 

 crown. The long, full crown means, however, a shorter, 

 clear- length and coarser logs from the upper stem. The 

 largest trees and the greatest yield in log measure are ob- 

 tained by the heavier grades of thinnings. On the other 

 hand, for the production of trees of high quality mod- 

 erate thinnings are made. In general, the best results are 

 obtained by making the thinnings during the first half of 

 a stand's life moderate, in order to secure good iorm of 

 trees, and then, after the main height growth is reached, 

 thinning heavily, in order to secure rapid growth in diam- 

 eter and volume. 



Condition of the Stand. — The considerations in the 

 previous pages are necessarily subject to modification, if 

 a stand is not regular or does not have a uniform density. 

 In many stands — in this country, most of them — there 

 are undesirable individuals in all crown classes. There 

 are dominant trees of poor species, trees of poor form, 

 defective trees, etc., which are cut whenever their removal 

 will benefit the stand. In a thinning designed to be of 

 the B grade, there might be taken out co-dominant or 

 even dominant trees, of undesirable character. So, also, 

 in a thinning designed to be of the D grade, there 



