EFFECT OF GRAZING ON WESTERN YELLOW PINE. 9 



age that continues through the season of abundant forage growth. 

 The fact that the needles and stems become tough and therefore less 

 palatable by September seems to account for the relatively little 

 damage that is done during the fall period, when ordinary forage 

 becomes dry and usually is closely grazed. 



In 1912 the time of making the first count extended until early in 

 June and in the preliminary study during 1910 until June 20. In 

 neither of these counts was serious damage recorded. In view of 

 this fact and of the indications based upon phenological observa- 

 tions, it is safe. to say that very little serious damage is done to the 

 reproduction before the middle of June. 



FACTORS INFLUENCING DAMAGE. 



INTENSITY OF GRAZING. 



Casual observations indicate that the amount of damage to repro- 

 duction is greater on heavily grazed areas than on those lightly 

 grazed. In order to determine the extent to which this apparent 

 relation holds and the intensity of grazing which may be permitted 

 without causing an undue amount of damage, plots were observed on 

 ranges representing various degrees of utilization. 



NORMAL GRAZING. 



Normal grazing, as the term is used here, implies that the class 

 and number of stock are well adapted to the character and amount 

 of forage. 



Observations during 1912, 1913, and 1914 on 92 plots, representing 

 a variety of forage types on ranges normally grazed by sheep, cattle, 

 and horses, showed that out of a total of 3,352 trees an average of 

 126 were injured, 258 were severely browsed, and 1,023 were moder- 

 ately to lightly browsed each year. Thus 384 trees, or 11 per cent 

 of the entire number, were severely damaged. 



Observations on 14 plots, containing 571 trees, on ranges normally 

 grazed by cattle and horses only, showed no trees injured during the 

 three-year period, none severely browsed, and only 11 moderately to 

 lightly browsed. The number of plots in this series is perhaps 

 insufficient to form the basis of general conclusions, but extensive 

 observations elsewhere bear out the belief that cattle and horses, 

 under proper conditions of grazing, do a negligible amount of 

 damage to forest reproduction. 



OVERGRAZING. 



B} r overgrazing is meant grazing by an excessive number of 



stock, with consequent injury to the palatable forage. Of 1,792 



trees on two plots on ranges overgrazed by all classes of stock, an 



average of 298 were injured annually, 335 were severely browsed, 



4205°— 17— Bull. 580 2 



