DETERMINATION OF THE QUALITY OF WOODS. 257 



by faulty treatment, by injurious external agencies, such as 

 drought, frost, wind, fire, insects, diseases of the trees, cattle 

 grazing, etc. 



For the preparation of working plans, only the actually 

 existing, or real, quality of the locality should be taken into 

 account, because the restoration of the normal quality is 

 generally a slow process, if it is at all practicable. As regards 

 the growing stock, both values are required, because the 

 normal quality represents the real quality of the locality, and 

 the real quality of the growing stock forms the basis for the 

 calculation of the yield, which the forest can at present give. 



On page 46 of Volume II. it has been said, that the quality 

 of the locality can be ascertained — 



(1.) By an assessment according to the several factors of 

 the locality ; or 



(2.) By an assessment according to a crop of trees produced 

 on the area in question, or on a similar soil in the 

 vicinity. 



It has also been stated, that the first of these two methods, 

 however carefully carried out, is always subject to grave 

 errors, because an examination of the chemical composition, 

 the physical properties of the soil and a determination of 

 the climate do not indicate the yield capacity of the locality 

 for forestry with any degree of certainty ; hence, it should be 

 used only as an auxiliary of the second method, or when the 

 latter is not available. 



Thus it will be seen, that the determination of the quality 

 of the locality depends practically on an examination of the 

 existing wood, which it has produced. In fact, a normal 

 growing stock is the true expression for the real quality of the 

 locality ; the same investigation gives both the quality of the 

 locality and of the existing crop. 



For the purpose of obtaining an actual figure, which repre- 

 sents the quality, the best way is to ascertain the volume of 

 the growing stock, including all thinnings, and the number of 

 years, in which it has been produced. In dividing the volume 



F.M. s 



