36 A PRIMER OF FORESTRY. 



work is impossible. The strips are usuall}^ not over 

 100 3^ards in width. Where the soil is dry, they are 

 run east and west to protect the young growth against 

 the sun, and are comparatively narrow. If there is 

 serious danger of windfall, the}^ lie at right angles to 

 the direction of the wind. 



These are the more important of the silvicultural 

 svstems. Thev have manv modifications, and indeed 

 each forest ma}^ 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 man}^ forests in the United States, and espe- 

 cially many woodlots, are in poor condition and unfit 

 for the immediate application of any silvicultural sys- 

 tem. They need to be put in order, and for that pur- 

 pose Improvement Cuttings are usually 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 tocutoftener 

 on the same ground than once in five years. Improve- 

 ment 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 



