FORESTRY — GRAVES. 265 



environment which they themselves create. For this reason forest 

 trees assimilate, grow, and bear fruit diflerently and have a different 

 external appearance and internal structure than trees not grown in 

 a forest. 



Forestry, unlike horticulture or agriculture, deals with wild plants 

 scarcel}^ modified by cultivation. Trees are also long-lived plants; 

 from the origin of a forest stand to its maturity there may pass more 

 than a century. Foresters therefore operate over long periods of 

 time. The}^ must also deal with vast areas; the soil under the 

 forest is as a rule unchanged by cultivation and most of the cul- 

 tural operations applicable in arboriculture or agriculture are en- 

 tirely impracticable in forestry. Forests, therefore, are largely the 

 product of nature, the result of the free play of natural forces. Since 

 the foresters had to deal with natural plants which grew under 

 natural conditions, they early learned to study and use the natural 

 forces affecting forest growth. In nature the least change in the 

 topography, exposure or depth of soil, etc., means a change in the 

 composition of the forest, in its density, in the character of the ground 

 cover, and so on. As a result of his observations, the forester has 

 developed definite laws of forest distribution. The forests in the 

 different regions of the country have been divided into natural types 

 with corresponding types of climate and site. These natural forest 

 types, which, by the way, w^ere also developed long before the modern 

 conception of plant formations came to light, have been laid at the 

 foundation of nearly all of the practical work in the woods. A forest 

 type became the silvicultural unit which has the same physical con- 

 ditions of growth throughout and therefore requires the same method 

 of treatment. The manner of growth and the method of natural 

 regeneration, once developed for a forest type, hold true for the 

 same tj-pe, no matter where it occurs. After the relation between a 

 certain natural type of forest and the climate and topography of a 

 region has been established, the forest growth becomes the living ex- 

 pression of the climatic and physical factors of the locality. Simi- 

 larly, with a given type of climate and locality it is possible for the 

 forester to conceive the type of forest which would grow there natu- 

 rally. The forester, therefore, may speak of the climate of the beech 

 forest, of the Engelmann spruce forest, of the yellow-pine forest. 

 Thus, if in China, which may lack weather observations, we find a 

 beech forest similar to one found in northern Xew York, we can be 

 fairly certain of the climatic similarities of the two regions. More 

 than that, a type of virgin forest growth may serve as a better indi- 

 cation of the climate of a particular locality than meteorological 

 records covering a short number of years. A forest which has 

 grown on the same ground for many generations is the result not 

 of any exceptional climatic cycle, but is the product of the average 



