EFFECT OF GRAZING ON WESTERN YELLOW PIXE. 5 



TABLE I. Annual damage to western yellow-pine reproduction, etc. Continued. 



In order to arrive at the number of trees damaged to such an ex- 

 tent as seriously to retard their growth, it is necessary, under the 

 plan of classification, to include only the injured, the severely 

 browsed, and the severely rubbed trees. Estimated on this basis, 

 1,493 trees, or 16.7 per cent of the total number examined, are sub- 

 ject to severe damage by grazing. It is this class of damage, rather 

 than the total damage, that is of serious importance. 



It is believed that the figures given represent fairly the actual 

 damage over approximately one-half of the yellow-pine type on the 

 Coconino Forest and that similar damage will occur elsewhere under 

 like conditions. Conditions under which the damage is greater or 

 less than the average are pointed out in the later discussions. 



DAMAGE BY HEIGHT CLASSES. 



The extent of damage done to trees of different sizes is shown in 

 Table II. 



The conclusions drawn from this table are that damage is most 

 severe in the seedling class and gradually shades off as the plants 

 increase in size; that injuries and serious browsing constitute nearly 

 all of the important damage to trees below 3.5 feet high, but that 

 above this height most of the serious damage is due to rubbing, which 

 becomes more acute with increase in height up to 5.5 feet. 



Figure 2, which is constructed from the data in Table II, shows 

 graphically the basis for these conclusions. 



