372 JOURNAL OF FORESTRY 



In 1908 Pearson made observations to determine grazing damage to 

 western yellow pine reproduction on the Coconino. He reported ® 

 damage to seedlings 1, 2, and 3 years of age under open range grazing 

 varying from 10 per cent to 28.2 per cent. On one plot typical of 

 driveways and bedding grounds he found a damage of 68.3 per cent. 

 His investigations showed that horses and cattle do little damage. 



Pearson's data are difficult to evaluate because he does not give 

 information as to the character of range, the time of grazing, the 

 intensity of grazing or the way in which the sheep were handled on 

 the area studied. 



His summary, however, that "sheep severely injure seedlings by 

 browsing, and to a less extent by trampling," undoubtedly was war- 

 ranted. His further conclusion that "sheep should, therefore, be 

 excluded from areas on which reproduction is desired" may have been 

 the right conclusion for the areas studied. It may, perhaps, be the 

 right conclusion for many other areas. It seems doubtful, however, 

 if the study upon which the conclusions were based was comprehensive 

 enough to warrant insistence upon carrying out such a policy without 

 qualification as to areas. 



Accordingly the observations started by Pearson were resumed and 

 expanded under his direction in 1910 and were followed up by Hill 

 in 1912, 1913,"^ and 1914. 



Hill's report, like Sparhawk's, requires careful study as a whole 

 for a thorough understanding of the results. For the purpose of this 

 paper, however, the essential data and conclusions are as follows : 



/. Average Amount of Injury: Over a period of three years on 250 plots 

 an average of 16.7 per cent of the seedlings up to oVa feet in height were se- 

 verely damaged each year and an additional 16.1 per cent were moderately dam- 

 aged. By severely damaged was meant that injury, if continued, would seri- 

 ously interfere with the development of the plants, resulting either in death or 

 prevention of ultimate development. Moderately damaged was applied to in- 

 jury which would not prevent the ultimate development of the tree, even if re- 

 peated in succeeding years until the tree developed beyond injury by grazing. 



An average of 21 per cent' of the seedlings below 6 inches in h»ight were 

 seriously damaged annually. The damage gradually decreased with increase in 

 height. 



° Pearson, G. A., Reproduction of Western Yellow Pine in the Southwest. 

 U. S. Dept. Agr., Forest Service Cir. 174. 



' Hill, Robert R., Effects of Grazing Upon Western Yellow-pine Reproduction 

 in the National Forests of Arizona and New Mexico, U. S. Dept. Agr., Bull., 

 580, Dec. 1917. 



