92 OUR NATIONAL FORESTS 



altitudinal limit of tree growth in that locality. 



Such studies as these, based upon systematic 

 meteorological observations, have an important 

 bearing on all other forest problems. The data se- 

 cured in this way especially assist the technical 

 foresters in solving the various problems in forest 

 management, reforestation, fire protection, and 

 land classification, besides giving positive knowl- 

 edge of the environment in which our trees live and 

 of the factors affecting their growth and reproduc- 

 tion. These systematic observations are of prime 

 importance if we ever hope to have a science of 

 American Forestry. 



Forest Management Studies. Experiments in 

 forest management are carried on to determine the 

 best methods of cutting National Forest timber to 

 secure natural reproduction and at the same time 

 to improve the quality and productivity of the re- 

 maining stand. These studies are carried on by 

 means of permanent sample plots, on which all the 

 trees are carefully measured and recorded. First 

 the timber is cut on the plots under different sys- 

 tems of management, or thinnings or improvement 

 cuttings are made. An exact record is kept of the 

 amount of timber removed and of the size and dis- 



