674 



Canadian Forestry Journal, August, ipi6 



How Plantations Are Thinned 



Preserving the Wind Belt, When to Commence Thinning, 

 Removing the Diseased and Dying Trees. 



By H. M. Morrison, 

 Porcupine Forest Reslerve, Usherville, Sask. 



If one is to be successful in rear- 

 ing timber for profit, there is, per- 

 haps, no branch more important 

 than a thorough knowledge of the 

 art of thinning and yet this is a sub- 

 ject on which there is considerable 

 diversity of opinion. What is the 

 object of thinning, one may ask? 

 Well, in the first place, it is to utilize 

 that material in the plantation which 

 otherwise would be rendered useless 

 by rivalry of the other trees. Twen- 

 ty to thirty per cent of the yield of 

 a plantation should be given by 

 thinnings. Thinning also stimulates 

 growth and helps the development 

 of the remaining trees and influences 

 the deeper production and time of 

 maturity of the plantation as a 

 whole. It improves the soil as well 

 as the remaining trees. It also pre- 

 vents the formation of knots and 

 useless branch wood. The life of 

 the plantation may be lengthened or 

 shortened by the mode of the thin- 

 ning ; when properly done and at 

 the correct time it should render the 

 remaining trees more proof against 

 wind, storms, snow, insects and 

 fungi. Final thinning is generally 

 carried out with a view to promot- 

 ing natural regeneration. In mixed 

 woods thinning regulates the pro- 

 portion of the trees in mixture. 



No unchanging rules can be laid 

 down for the thinning of planta- 

 tions, it is to a great extent a mat- 

 ter of experience and good judg- 

 mert. l)':t l!^c following gv^ieral 



principles may be of use to those 

 who undertake this work: 



1. Study the relationship of trees 

 and soil and act accordingly. 



2. Begin to thin at the correct 

 time and most sheltered spot. 



3. Cut away all diseased and 

 dying trees. 



In thinning young or old planta- 

 tions the work must always be sub- 

 ject to modification, according to 

 the nature of the trees and soil and 

 the ultimate use of the plantation 

 which is being operated upon, and 

 much forethought and discrimina- 

 tion are required. 



When to Commence. ^ 



One of the most important things 

 in thinning plantations is to knoAv 

 when to commence the operation. If 

 it be delayed too long, the result is 

 stems whose length is out of all pro- 

 portion to their diameter. Such 

 trees have not sufificient stem de- 

 velopment in girth to withstand 

 wind, storms, or snow whose weight 

 they cannot bear. As a general rule 

 thinning should commence when 

 the plantation is from 20 to 25 years 

 old and should be repeated at from 

 intervals of from 5 to 10 years. 

 When trees have finished height 

 growth and have developed clean 

 and branchless stems, thinning 

 gives them niore soil-room and light 

 and thus increases nutrition. It also 

 produces broader year rings and 

 wood of better quality. Without it 

 the wood is apt to be soft and 

 springy. 



