148 transactions of royal scottish arboricultural society. 



Breast-height Form-factors of Stands. 



Let us assume that every tree in the stand has the same form. 

 Since the vigour and rate of growth of the individual trees vary, 

 the heights, volumes, and basal areas also vary. 



In a very young wood, when the trees are very small, the 

 form-factor is, theoretically, -coo. In a slightly older wood, the 

 smallest trees are still -ooo, but some of the larger trees 

 approach '500, while the majority lie between these two figures. 



Tk; 19. 



Still later, quite a number of trees reach and pass the maximum. 

 In the case of trees with the degree of taper selected for this 

 article, the maximum would be reached when the girth at 

 breast-height was 13I inches. 



At a still later stage, the majority of the trees will have 

 passed the maximum, and the form-factor of the whole stand 

 begins to drop. Still later, all the trees pass the maximum and, 

 theoretically, all the form-factors are less than '500. 



Fig. 20 shows graphically how the form-factors vary with 

 girth in very young, young, and old stands. 



Having now obtained some idea of the mathematical varia- 

 tion in the breast-height form-factors of single stems and stands, 

 due simply to increase in size, let us consider a few of the other 

 things which may cause variation in this type of form-factor. 



