48 



it condenses aqueous vapors, carbonic- acid gas, and ammonia from the 

 atmosphere, which, together with the carbonic acid-gas it develops, 

 assists the decomposition of the mineral substances in the soil. 



SUBSOIL. 



The subsoil, if different in nature from the soil, should be described 

 in the same manner as the soil. 



SOIL COVER. 



Under soil cover is meant the weedy or herbaceous forest plants that 

 grow in the soil. It should be noted, because frequently such weeds 

 indicate the quality of the soil. 



FOREST CONDITIONS OF SAMPLE AREA. 



In describing the forest conditions of the sample area it is advisable 

 to be as concise as possible. The blanks left for the composition of for- 

 est should be filled out after the measurements of the acre yield have 

 been taken, because then the proportion in which the species found in 

 the forest area mixed may be accurately determined. Very small trees, 

 such as those under 3 inches in diameter (breast high) and under 20 

 feet high, should be counted separately and be considered as under- 

 growth. All shrub forms shoald also be mentioned as a part of the 

 undergrowth. 



The description of the sample area is usually concluded with general 

 remarks relating to the appearance of the stand of trees, development 

 of crowns, quality of timber, average ages of the species composing the 

 stand, and such other items as may for any reason be found necessary. 



DENSITY OF FOREST. 



The density of a forest is usually judged by it's canopy or degree of 

 contact of the crowns of the trees. When the crowns are in touch with 

 each other, forming a close canopy, the density is considered normal 

 and the forest fully stocked. This condition is designated by a unit. 

 The degrees of opening of the crown cover are expressed in decimals, 

 thus permitting the making of 10 degrees of density. The density 

 factor is simply a short expression of the light conditions of the for- 

 est, and the 10 degrees are established not with the expectation of 

 getting the exact mark of density, but to enable the forester to indicate 

 it with more facility. It is not worth while to puzzle the brains over 

 the solution as to whether the density is 0.5 or 0.6, especially when it 

 is remembered that the method of designating tlie density is in itself 

 imperfect and mostly based upon the general impression of the 

 forester. 



