6 BULLETIN 738, U. S. DEPARTMENT OF AGRICULTURE^. 



The species and height of all seedlings on the plots were recorded 

 at the beginning and end of each season, and in many instances at one 

 or more other times during the summer. Injuries due to grazing or to 

 other causes were noted at the same time. Record was also made of 

 the approximate date when each plot was grazed, and of the intensity 

 of grazing. 



INJURIES TO REPRODUCTION CAUSED BY SHEEP GRAZING. 



NATURE OF INJURIES. 



Sheep injure forest reproduction directly both by browsing and by 

 trampling. In the case of browsing the injury may be confined to a 

 few needles or to the tips of side branches, the leader may be bitten 

 off, or the bark may be gnawed. With conifers such injuries, except 

 in extreme cases or when repeated, seldom result in permanent deform- 

 ity or death. A careful study of comparative heights of uninjured 

 seedlings and of those whose leaders had been removed several years 

 before showed no perceptible difference in the rate of growth, except 

 for the loss of the one year's increment. An uninjured side branch or 

 a new bud takes the place of the leader, and the slight crook in the 

 stem, which is evened out as its diameter increases, usually disappears 

 within 10 years. 



If the injury is repeated every year or two, of course the seedling 

 will be permanently .stunted and will never become a tree. This has 

 happened along driveways which have been used for many years, and 

 also on bed grounds which have been used several nights at a time 

 year after year. It seldom happens except in such places. If an 

 average of 1 per cent of the seedlings on an area are injured by grazing 

 in one year, only 1 per cent of this 1 per cent will be likely to suffer 

 a second injury the next year. In 20 years only 1.7 per cent of the 

 seedlings will be likely to have been injured twice, and only 0.1 per 

 cent three times. 



Very severe browsing, such as frequently occurs on bed grounds 

 which have been used too much, often kills the seedlings outright. 

 In order to test the recovery from such injury, a number of seedlings 

 between 6 inches and 3^ feet high were entirely defoliated in 1913. 

 One year later 20 out of the 42 were dead, and the others, although 

 they had put out new needles, appeared to be unhealthy and likely to 

 die later. To test the effect of light browsing, only the foliage put 

 out during the current year was removed from a number of other seed- 

 lings. This had no apparent lasting effect, since all were fully recov- 

 ered within a year. 



By trampling, sheep may bruise the seedling, bury it under loose 

 soil or litter, uproot it, or break it. Such injuries, especially in case 

 of the smaller seedlings, often cause death. 



