WITH THE HELP OF YIELD TABLES. 109 



Generally, the method is better adapted to woods which 

 have passed middle age than to younger woods, as in the latter 

 the factors of the locality have not in all cases found full 

 expression. In the case of very young woods it is altogether 

 useless to measure the volume for the purpose of selecting 

 the proper yield table. For such woods the quality class 

 must be selected by means of an older wood growing in the 

 vicinity on a locality of similar quality. The same procedure 

 is followed in the case of blanks ; if no such older wood is 

 available, the soil and climate must be examined and the best 

 possible estimate of the quality made accordingly. 



As the measurement of the volume takes much time, and as it 

 is difficult to estimate the exact proportion between the actual 

 and normal stocking, it has been proposed to select the proper 

 yield table for a wood by means of one factor only of the 

 volume. It has already been explained that of all, such as 

 number of trees, diameter, form factors, basal area and height, 

 the last is the most suitable. Indeed, actual investigation 

 has proved that in the case of all woods of middle age and 

 upwards the volume of two woods, other conditions being the 

 same, is fairly proportionate to their mean heights. The 

 mean height is, therefore, an excellent indication of the 

 quality class ; it, as well as the age, are comparatively easy to 

 ascertain. In selecting the appropriate yield table the mean 

 height is used in the same way as has been described for the 

 volume. If the height agrees with one of the heights given 

 in the yield table for the same age, the increment can be read 

 off directly. If it differs, the nearest is selected and the incre- 

 ment of the table modified in proportion to the difference be- 

 tween the actual height and that given in the table. If, more- 

 over, the wood is not fully stocked, the increment given in the 

 table must be further modified in the manner indicated above. 



The height is no true indicator of the quality for young 

 woods ; for such, as well as for blanks, other woods growing 

 in the vicinity must be utilized, or the soil and climate 

 examined. 



