270 COLLECTION OF STATISTICS. 



for the Scotch pine prepared for Germany may safely be used 

 in the south of England. The fact is, that the sources of 

 inaccuracy inherent to the best methods of measuring the 

 volume of a standing crop are greater than those caused by 

 using general yield tables for any particular locality. 



The general yield tables given at page 386, Appendix D, 

 are used in Saxoii} r for the determination of the quality class. 



The quality of young woods cannot be judged by their 

 volume, since the factors of the locality may not yet have 

 found full expression in the volume ; here the quality must 

 be estimated by the general condition of the crop, and especi- 

 ally its height growth. Indeed, the latter may be used even 

 in older woods, as long as height growth has not ceased. 



The determination of the quality from yield tables in the 

 case of clear cutting in high forest and in coppice is a simple 

 matter, as previously shown. The regeneration area under the 

 shelter-wood system gives some trouble, because it is no longer 

 fully stocked, so that the volume does not represent the 

 quality ; here the determination must be based upon an inves- 

 tigation of the quality of the locality combined with the con- 

 dition of the shelter-wood and young growth. A similar 

 procedure is followed in the case of coppice with standards, 

 and in selection forests. The quality of blanks is estimated 

 from the soil and climate, or from that of adjoining woods 

 which have been produced on soil of a similar description. 



c. Determination of the Quality by the Final Mean Annual Increment. 



This method has sometimes advantages, especially if the 

 areas are to be reduced to one common quality ; but it has the 

 great disadvantage that the final age of each wood must be 

 fixed, since the mean annual increment changes with the age at 

 which the wood is cut over. Moreover it is almost impossible 

 to fix the final mean annual increment without the help of 

 yield tables. 



