Canadian Forestry Journal, May, ig20. 



229 



<% 



"^i^ 



A Ranger's cabin and lookout tower, north of the 

 Canadian National Railways ia the Cochrane, Ont., 

 forest protection district. Photograph by courtesy 

 of Ernest G. Poole. 



The purpose of thinning- is to 

 stimulate the growth by giving each 

 tree sufl'icient light and space to de- 

 velop and yet keep a complete cover 

 over the entire area of the woodlot 

 so that the sun and wind will not de- 

 teriorate the soil. A large proportion 

 of any tree has been derived through 

 the leaves from the air and sunligln 

 and foliage are ^•ery necessar\- agents 

 in its growth. Shading- or cnnvding 

 which interferes with the (le\clo]i- 

 ment of the lea\es niu->t neoe->sariI\ 

 check the growth. To keep trees too 

 l"ng in a crowded condition is iu)t 

 adxisable. Since other things l)eing 

 equal, the tree receixing the most 

 light will produce the most wood. We 

 must at the same time he careful and 

 not go to the other extreme and grow 

 our trees in stands which are too 



open, for our object is not merely to 

 secure wood in quantity; we also' de- 

 sire quality. \\'e require the wood 

 in a form in which we can best use 

 it. Ordinarily the form we most de- 

 sire it in, is long straight trunks, clean 

 of stubs and branches. \\q must, 

 therefore, remember that trees grown 

 too much in the open do not have de- 

 siral)le trunks, since it is characteris- 

 tic for a young and vigorous tree to 

 spread out and take all the space it 

 requires, and to develop a low bushv 

 head in a comparatively short trunk. 

 To secure tall, clear trunks we must 

 keep the young trees sufficiently 

 crowded to prevent the crown or head 

 I)ecoming too spreading. ^^'e must 

 cause the lower branches to be killed 

 oil by shading when they are com- 

 paratively small, so that they will 

 leave no large stubs to form knots in 

 the sawn material. By crowding the 

 trees from the time they are quite 

 small, and from time to time thinning 

 them as they require it, we can retain 

 a sufficient amount of shade to cause 

 the pruning to take place but at the 

 same time, permit the tree to have 

 enough light to keep u]) a good rate 

 of growth. 



Which Trees Need Most Light? 



A woodlot composed o\ on]\- a 

 few species is much easier to thin j^ro- 

 j)erly than one coni])o>ed of \-erv 

 many kinds of trees, and especially if 

 they are of diff'erent ages. In the fol- 

 lowing list the trees ha\e been group- 

 ed according to their light rcduire- 

 nuMit^. This order is not absolutelv 

 tixed. 1)iit will he found to \arv 

 Somewhat in dirfcrent loealities. 

 ^lUlng trees as a rule will tolerate 

 more sjiading than those nearer ma- 

 ture. I'rees growing on a site not 

 suited to them will retjuire more 

 lii'lit than it tluw h.id i)roper soil and 

 nil ii>lni\' ci Miditii mi>. 

 Shade Bearers: .^ugar Maple: l>eech 



Hemlock: l'>alsam fir: ."spruce 



White cedar: ."^iKi'r Maple: Red 



I'dm : I'.asswood. 

 Intermediate: Chestnut: liirch : White 



I'ine : r.lack W .ilnut : Sycamore; 



r.lack Ciierrv : (^ak-. 



