PRACTICAL POKESTRY. 



19 



These are the most important of the silvicultural systems. They 

 have many modifications, and indeed each forest may require a 

 special form of its own, which must be devised or adapted for it by 

 the forester. But whatever the form, the object is always to use the 

 forest and provide for its future at the same time. 



Improvement cuttings. — ^Very many forests in the United States, 

 and especially many woodlots, are in poor condition and unfit for the 

 immediate appHcation of any silvicultural system. They need to be 

 put in order, and for that purpose improvement cuttings are usually 



Fig. 11.— Spruce managed under the strip system. Southern Russia. 



required. In the end these cuttings should remove all trees which 

 the forest is better without, but they should be made gradually, so 

 as not to open the cover too much and expose the soil to the wind and 

 the sun. In general, it is unwise to cut more than 25 per cent of the 

 poles and older trees in a dense mature forest, or to cut oftener on 

 the same ground than once in five years. Improvement cuttings of 

 course should never fall on trees which are to form the future crop, 

 but they should remove spreading older trees over promising young 

 growth; poor trees which are crowding more valuable ones; unsound 

 trees whose places will be taken by others of greater value, or which 

 are themselves becoming less valuable from year to year; and seed 



358 



