form-factor in coniferous trees. 149 



Variation due to Bark per cent. 



We have dealt, for the sake of simplicity, with the Over-bark 

 Breast-height Form-factor. It is the Under-bark type, however^ 

 which is in practical use. Since the volume under bark is, of 

 necessity, less than the volume over bark, while the height and 

 basal area remain the same, the under-bark form-factor of any 

 tree is bound to be less than its over-bark form-factor. This 

 difference is not, of course, constant for every species, nor for 

 every locality. Thus, of two trees with the same over-bark 



Very You N(; 

 YooNq. 

 Old Wood. 





Ttq 20. 



form-factor and of the same height and basal area, one a larch 

 and the other a spruce, the under-bark form-factor of the former 

 will be much less than that of the latter. 



Influences Tending to Increase the Form-factor — 

 i.e. an increase of volume without corresponding 

 increase in height or girth. 



1. Volume increase taking place largely in the upper part of 

 the stem. This is probably what occurs in dense stands where 

 the crowns are confined to the upper parts of the trees. 



2. Forking — causing increase of volume without increase of 

 height. This increase would also take place for the most part 

 above breast-height. 



3. Loss of leader, or point, from any cause whatever, so 

 reducing height without any reduction in volume. 



