10 BULLETIN 580, U. S. DEPARTMENT OF AGRICULTURE. 



and 474 were moderately to lightly browsed. Thus 633, or 35 per 

 cent of the total number, were subject to severe damage. 



Of 522 trees on 14 plots on an overgrazed range open to cattle 

 and horses only, an average of 11 were injured annually, 55 were 

 severely browsed, and 194 were moderately to lightly browsed. Thus 

 66 trees, or 13 per cent of the total number, were subject to severe 

 damage. This injury is not excessive in itself, but when compared 

 with the negligible injury which cattle and horses cause on nor- 

 mally grazed areas, it forms an* additional reason for insisting upon 

 the protection of the range against overgrazing, especially on areas 

 where all of the established reproduction is needed. 



The general conclusions from these observations are: (1) That 

 on ranges properly grazed by sheep as well as by cattle and horses, 

 a very considerable amount of damage occurs, but that where only 

 cattle and horses graze under such conditions a negligible amount 

 of damage results; and (2) that where overgrazing occurs serious 

 damage is caused by any class of stock. 



DENSITY, AMOUNT, AND CHARACTER OF FORAGE. 



DENSITY OF FORAGE. 



Since the intensity of grazing has a direct relation to the severity 

 of the injury to tree reproduction, the inference might be drawn 

 that on a range supporting a scattered stand of forage plants the 

 percentage of trees damaged would be materially greater than on 

 a range where the stand of forage is good. In order to determine 

 whether this is so, observations were made on ranges where the 

 average density of forage plants was less than two-tenths, and on 

 ranges where the average density was four-tenths of the ground 

 surface. The plots were selected as representing all degrees of graz- 

 ing. On 39 plots supporting a good stand of forage and 1,010 trees, 

 31 trees were injured, 119 were severely browsed, and 255 were mod- 

 erately to lightly browsed. Thus 150, or 15 per cent of the total, 

 were subject to severe damage. On 92 plots, containing 3,678 trees, 

 on range poorly stocked with forage, 157 trees were found to be 

 injured, 500 severely browsed, and 882 moderately to lightly 

 browsed. Thus 18 per cent of the total were being severely damaged. 



These comparisons indicate that under average conditions there 

 is not a great deal of difference in the amount of damage done on 

 ranges well stocked with forage plants and on ranges poorly stocked. 

 In general, therefore, it may be concluded that in a given forage 

 type, with the same amount of forage allotted each animal, the 

 density of the forage has little relation to the amount of damage to 

 pine reproduction. 



