58 A MANUAL OF FORESTRY 



Where there is danger of windfall in leaving single trees small 

 groups of three to ten or more seed trees are left standing together. 

 This is done to better prevent windfall. 



Where trees are left for seed alone, inferior individuals may be 

 retained. If trees are left for greater growth as well as for seed, 

 only straight, thrifty specimens are reserved. This modification 

 is well adapted to stands of moderate age where there are many 

 trees capable of continuing a thrifty growth for years, probably 

 for another rotation. If, for example, the rotation used in white 

 pine were seventy-five years, these reserves or standards might be 

 left over one rotation, until they were one hundred and fifty 

 years old, when they would be very valuable for special purposes, 

 as for derrick sticks, besides having served as seed trees. While 

 under the previous method less than a dozen trees per acre are 

 required for seeding, under this system from 15 to 25 reserves 

 per acre may be left. Naturally the reproduction is better on 

 this account. 



D. THE SHELTERWOOD METHOD. 



There are certain disadvantages connected with all of the 

 clear-cutting methods which are overcome by shelterwood. 

 Under the former methods the soil is exposed and reproduction 

 is retarded by drought and frost. It is also impossible to use 

 them with heavy-seeded trees, such as oak, chestnut, and beech. 



The principle of shelterwood is to open and remove the stand 

 gradually by a series of thinnings. This results in reproduction 

 under the shelter of the mother trees which are not all cut until 

 complete reproduction has been accomplished. A more even 

 distribution of seed results because there are large numbers of 

 seed trees well distributed over the area, and the young seedlings 

 arc- protected by the shade of the remaining trees. The mother 

 trees also benefit from the thinnings and make a more rapid 

 growth during the remainder of their lives. 



The method can be applied only with wind firm species or where 

 there is no danger from windfall, as the system of cutting leaves 

 many trees isolated. On account of the gradual removal of the 



