446 



FORESTRY AND IRRIGATION 



October 



In the semi-arid regions, what are 

 the relations between moisture defi- 

 ciency and seed production? 



In the same section, The Great 

 Plains, what species are best adapted 

 to planting and what is the proper 

 treatment for each? 



What degree of shade does a given 

 species require? How much shade 

 will it tolerate ? How do these factors 

 vary with the age of the trees and in 

 different situations? These questions 



orable, with the cost and advantage of 

 changing natural types of forest, with 

 the relations that exist between the 

 members of various forest types. 



It will not be supposed that work 

 in any direction must halt until each 

 question is answered. Daily work in 

 the forest helps to answer them. Nev- 

 ertheless, something more is required 

 and the method of sample plots is re- 

 sorted to. These are called permanent 

 sample plots when they are established 



Permanent Sample Plot in a Western Yellow Pine Pole Wood to Determine 



the Effect of Heavy Thinning. 



are vital to the production of forests 

 anywhere, whether the seeding be nat- 

 ural or artificial. 



What effect has frost upon the de- 

 velopment of a plantation and a for- 

 est? 



What is the relation of a given spe- 

 cies to various soils, aspects, and alti- 

 tudes? 



Iiroader problems will deal with 

 the possibility of establishing forests 

 where conditions are extremely unfav- 



and maintained in such a way that 

 every change which takes place within 

 them can be observed and recorded. 



In practise it is necessary to find a 

 place where every condition is as near- 

 ly ideal as possible, and to lay off the 

 plot so that everything affecting it 

 shall be entirely normal. The area is 

 usually rather small, rarely more than 

 half an acre, because it is hard to find 

 larger tracts having the necessary uni- 

 fomity, and hard to control them. 



