29(\ TENDING OF CROWDED WOODS AFTER EAUEY YOUTH. 



increases the ilitYerence, leading to the formation of trunks 

 whicli consist of a niimher of broad rin^^'s in the inner i)art, 

 surroinided by a series of narrow ones. Such timber is for 

 many purposes of smaller value than if the rings are of 

 uniform breadth throughout. 



As regards the density of the timber, a distinction must be 

 made between the various species. In the case of those broad 

 leaved species which have the pores in the spring portion of 

 the wood, broad rings indicate high density, and narrow rings 

 comparatively low density ; here, then, heav^y thinnings are 

 indicated. The same prol)ably holds good for species which 

 have the pores uniformly distributed over the ring. In coni- 

 fers, however, the matter is reversed, as in their case broad 

 rings usually represent low density and narrow rings high 

 density ; consequently heavy thinnings must be avoided, at 

 any rate up to a certain age. 



On the whole it may be said that, in the production of 

 higli-class timber, heavy thinnings at an early age should be 

 avoided. The rule here, according to which the thinnings 

 are to be made, must run as follows : — 



The wood sliould be thinned lightly until towards the end 

 of the principal height growth. Then the thinnings should 

 gradually become heavier, so as to assist a selected number 

 of trees by the gradual removal of all those which are inferior 

 and diseased ; in other words, the thinning is then done more 

 in the dominating and dominated trees than in those which 

 have been left behind in the struggle for existence and no 

 longer compete ; the latter, if capable of living on, may be left 

 to assist in the protection of the soil or to act as wind brakes. 

 This method of thinning is called " eclaircie par le haut " 

 in French, and " Hochdurchforstung " in German. 



4. TJiiintiiKi of Mixed ll^oods. 



In the foregoing pages the theory of thinning as applicaljle 

 to pure woods has been given. Generally, the points aimed 

 at are to stimulate producticm and to develop the most suitable 



