8 A MANUAL OF FORESTRY 



oak, ash. maple, chestnut, beech -seem to demand the presence 

 oi" a considerable quantity of potash; spruce, fir, pine, and birch 

 thrive on soils rich neither in lime nor potash. For the produc- 

 tion of wood only, the demands vary as follows in high forests: 

 from 4 to 20 pounds of lime; from 2 to 10 pounds of potash, and 

 from I to 4i pounds of phosphoric acid per acre per year. The 

 Combined influence of all these factors dependent on soil and 

 situation is shown in the amount of timber produced per acre 

 and in the quality of the timber. 



When the trees of a wood are tall and straight, free from 

 branches, and tapering but little, it is the best possible indica- 

 tion that the soil and situation are eminently suited to the wood- 

 land crops growing on them. 



These factors of climate, soil, etc., have influenced the dis- 

 tribution of trees in such a way as to form forest "types." In 

 crossing a mountain ridge we find one type of forest in the 

 swamp at its base, which is quite distinct in its composition 

 and appearance from that on the drier, rolling land just be- 

 yond. On the steeper slopes another forest type is substi- 

 tuted, just as the human type raised in the wild mountains 

 differs from that of the fertile valleys below. Scientific forestry 

 largely deals with the causes for these varied types, while applied 

 forestry, based on this knowledge, tries to develop in every 

 locality the type which is best fitted to exist there. 



The term stand is a general descriptive term referring to an 

 aggregation of trees standing on a limited area, of more or less 

 uniformity of composition and condition, or of age. Thus in a 

 (c-rtain type we may have a stand of young growth; a stand 

 of diseased and damaged trees; a stand of exceptionally tall 

 specimens, etc. These stands are usually confined to a compara- 

 tively small an a. 



FOREST TYPES. 



In every forest the ceaseless struggle going on gradually 

 brings about many changes unseen by the casual observer. 

 In the small openings of the forest, caused by windfall, snow 



