178 INTERMEDIATE CUTTINGS — THINNINGS 



opment. The trees capable of furnishing the largest propor- 

 tion of clear lumber in the final cut will be found in the 

 intermediate crown class. They have long clear boles which 

 have been thoroughly pruned while still slender and all subse- 

 quent growth will be clear Ivtmber. Borggreve in his succes- 

 sive thinnings, removing the relatively poorly formed domi- 

 nant trees, advances the intermediate trees to the co-dominant 

 and finally to the dominant crown class: — from a position 

 where only a small amount of overhead light was available 

 to a commanding place in the stand with opportunity for 

 rapid growth. In theory trees found in the overtopped class 

 at the time of the first thinning might eventually be advanced 

 to the dominant class. (See Figs. 71, 72 and 73.) 



The success of Borggreve's method hinges upon whether 

 trees which have been crowded and overtopped in the struggle 

 for existence can recover and become thrifty fast growing 

 individuals. Undoubtedly the degree to which the process 

 of suppression has advanced is the determining factor in such 

 recovery. The extent to which overtopped and intermediate 

 trees can be expected to develop into first class dominant trees 

 will vary with the silvical habits of the species and the site 

 and must be determined in each case. With shade enduring 

 species and on the better class of sites there is more oppor- 

 tunity for the use of Borggreve's principle than with hght 

 demanding species, which suffer more severely from suppres- 

 sion, and on poor sites when recovery and rate of growth 

 after thinning is slow. 



At first thought it might seem that a series of selection 

 thinnings, if continued long enough, must eventually produce 

 an unevenaged stand and thus be properly classed as repro- 

 duction cuttings under the selection method, rather than as 

 intermediate cuttings. This is not the case. The selection 

 thinnings are continued only until the reproduction period is 



