THE SWISS METHOD OF REGULATING THE CUT IN PRACTICE 569 



The same diameter classes were chosen for each of the species in the 

 Catskills, 16 inches d. b. h. below which no sound and thrifty timber 

 should be cut and 18 inches d. b. h. as the maturity limit above which 

 the timber is growing so slowly as to be judged overmature. 



The diameter and maturity limits are not uniform for the various 

 species in the Peninsula State Park. Since pulp wood can be cut from 

 smaller trees than can saw logs, the diameter limits are bound to vary. 

 The maturity limit was fixed where the current annual increment falls 

 below 2 per cent. 



The technical rotations and the diameter limits for the species on 

 both tracts of land can be seen from Tables 4 and 7. 



Although several methods were used in determining the cut for 

 each working plan, the results obtained by use of the Swiss Method were 

 given the most weight, and the other methods merely used as checks. 

 Tables 4 and 5 show the relative volumes of the size classes {"Y" and 

 " Z"), the increments {"Xi" and "Yi"), the length of cutting cycles,* 

 and the allowable annual cuts as determined by the use of these data 

 in the Swiss method. It will be remembered that the cutting cycle 

 here is the number of years during which the volume of the oldest size 

 classes must last, and is obtained by dividing the volxmie of the older 

 size classes by the annual increment of the forest.^ With this in mind, 

 the reason for the difference in length of cutting cycles for the two 

 tracts of forest is readily apparent. The volume of timber in trees 

 over the diameter limit and under the maturity limit (class "Y"), 

 and the increment on classes "X" and "Y" {"Xi" and "Yi") will 

 determine the number of years in the cutting cycle. Where there is a 

 large amount of timber in class " F," and a relatively low increment, a 

 long cutting cycle is found to result. This condition is found in the 

 forests of the Catskill tract. Beech and birch are examples of cutting 

 cycles of average length. With the hemlock there is a relatively high 

 increment in proportion to the amount of timber in class "Y," and the 

 result is a shorter cutting cycle. With the maple the conditions and 

 results are reversed. 



* The varying lengths of cutting cycles in the two tracts of timber are perhaps 

 the most noticeable features in Tables 4 and 5. 



Y 



* CC= ^. , ,.. The surplus growing stock "Z" should play no part in deter- 



Xt-\- It' 

 mining the cutting'cycle, " CC," (F. Q. XIV, No. 2. p. 264). 



