64 



BULLETIN 55, U. S. DEPARTMENT OF AGEICULTUKE. 



culling the forest of trees of certain diameters. It requires, however, 

 great regularity and exactness in logging operations, and may there- 

 fore present difl5culties, although it is being practiced to a considerable 

 extent in private and State spruce forests abroad. 



Thinned and. partialhj cleared strips.- — Another modification of the 

 system of clear cutting in strips is especially applicable to large 

 stands of mature timber. Watersheds, or other logging units large 

 enough to allow logging on the same area for a period of five or six 

 years, are divided into strips, all of which are cut over within the 

 five or six year period, but only for two-thirds of their full width. 

 Thus, if the width of the strips is 150 feet, each strip is cut only 100 

 feet. On the remammg 50 feet of each strip the timber is merely 

 thinned (fig. 8). As logging operations on the area will go on for 

 five or six years, there should be one or two good seed years during 

 which the logged areas will be reproduced from the adjoining 50-foot 



S 



Fig. 8. — Partially cleared and thinned strips. Each strip is cut only for two-thirds of its width. On the 

 remaining one-third the timber is only thinned. Reproduction takes place on the adjoining clearings 

 and under the thinned stand. When reproduction is secured, the remaining one-third of the strip is 

 cut clean. The entire logging area is reproduced within five or six years. 



Strips of timber. Since 50-foot strips are thinned, reproduction 

 will occur on them. As soon as young growth appears on the clear- 

 ings and under the trees left uncut, the 50-foot strips are also taken, 

 and the entire area is thus cut and reproduced within a few years. 

 This method of cutting is simple and, under favorable conditions, 

 practical as a logging proposition. The great danger is from windfall, 

 to which thinned stands are particularly susceptible. 



While often, as in cutting for pulp, clear cutting in strips is the best 

 method, even with the greatest precautions cleared strips often fail 

 to reproduce naturally with the desired species. No matter what 

 modification of the system is practiced, the narrower the strip the 

 greater are the chances for successful natural reproduction. When 

 abundant young growth exists under the old trees, clear cutting 

 need not be in the form of strips, but may cover the entire area 

 bearing reproduction. 



Clear cutting in strips must naturally lead to an increase of balsam 

 in the second growth, since it is a proHfic seeder and requires more 



