THE SHELTERWOOD SYSTEM 165 



ture stand of spruce and fir, there are a number of groups 

 of advance growth, from 20 to 50 feet in width, of 

 the character shown in Fig. 30. The center of a given 

 group stands under an open or broken canopy, and there 

 the trees are the tallest. The group extends under the 

 denser portion of the canopy, obtaining enough side 

 light from the central opening for life. 



The first cutting, which may be called the primary 

 cutting, is designed to uncover the larger of the young 

 growth, to give more light to the less vigorous trees near 

 the edge of the group, and to induce an extension of the 

 group in all directions. 



It might happen that an actual clearing would be 

 made over the center of the group, while over the border 

 trees there would be a heavy thinning, and still beyond 

 there would be a lighter thinning. In fact, one would 

 actually be making a final cutting over the center of the 

 group and a removal cutting over the remainder of it, 

 while immediately beyond the edge of the group the 

 thinning would resemble in severity a seed-cutting. 

 One could go farther, and if the forest were dense 

 immediately beyond this point, a thinning resembling 

 a preparatory cutting could be made in a still wider 

 circle. 



All the groups are thinned as just described. Sup- 

 pose that the thinnings have been successful, and that 

 reproduction has taken place beyond and around the sev- 

 eral groups. They will then be extended a distance of 

 from 50 to 100 feet. A secondary cutting is then re- 



