44 



least to sncli spots of the lumber area where the species fs found in 

 primeval forest conditions and not affected by natural dangers. The 

 spots selected must be carefully and minutely described, accompanying 

 the description by a sample area staked off exactly in the place where 

 the trees will be afterwards felled and measured for analysis. Blank 

 No. 2 in the appendix may be conveniently used both for description 

 and measuring purposes of the sample area, which should be, if possi- 

 ble, an acre in extent. The method of taking the acre-yield measure- 

 ments has been discussed in one of the preceding chax^ters. As regards 

 the description of the sample area, the example given in the blank 

 shows exactly how it should be done. 



ASPECT. 



In a mountainous country the aspect or exposure must be noticed, for 

 It exerts an influence on the climate and hence upon the growth of trees. 

 The northern aspect has diffused light, comparatively little heat, and 

 the soil, due to low temperature, remains moist, thus favoring rapid 

 growth. The eastern aspect is the most favorable for forest vegetation, 

 because the sun shines obliquely and during the coolest hours of the 

 day; the temperature and the light are moderate, permitting the soil 

 to retain its moisture, which again favors active growth. 



The southern exposure has the sun almost all day, causing intense 

 light, heat, and high temperature, which dries the soil rapidly and, con- 

 sequently, retards tree growth. On the western exposure the sun 

 shines during the hottest hours; again the high temperature makes it 

 difficult to retain the moisture of the soil. Of course, the nature of 

 the prevailing winds will modify the influence exercised by the expos- 

 ure upon tree growth, and it is desirable, therefore, to note the direc- 

 tions of the wind, its velocity, and the amount of moisture and heat 

 with which it is charged. It should be also mentioned that on north- 

 ern and eastern exposures, especially on the northern, vegetation is 

 retarded and the trees usually escape spring frost, but are apt to suffer 

 from early autumn frost, owing to the incomplete lignification of their 

 shoots. On southern and western exposures vegetation begins early 

 and young forests often fall the victim of spring frosts. 



SOIL AND DRAINAGE COXDITIOXS. 



In describing the soil it must be borne in mind that the fertility of a 

 soil for sylvicultural purposes is determined by its physical properties 

 rather than by its chemical composition. Forest vegetation requires 

 little inorganic matter. The amount of inorganic matter barely exceeds 

 one-half of that required by agricultural products, and then a great 

 portion of it is returned to the soil by the fall and decomposition of 

 the leaves and branches. The mineral constituents absolutely neces- 

 sary for the growth and development of trees are: Potash, calcium, 

 iron, magnesia, phosphorus, and sulphur. Most soils contain these 



