REPRODUCTION OF WESTERN YELLOW PIXE. 123 



tremely heavy losses from natural causes, it has been difficult to get 

 reliable information in regard to the damage by grazing. In the 

 studies prior to 1919. from 95 to 100 per cent of the seedlings on the 

 protected as well as on the unprotected plots died from causes other 

 than grazing : thus, although grazing damage was usually apparent, 

 the number of seedlings left formed an inadequate basis for conclu- 

 sions. Hill's records for the most part consider only seedlings beyond 

 the first year. He states that except during a succession of unusually 

 favorable summers, nearly all of the first-year seedlings die from 

 causes other than grazing, and therefore a record of damage by 

 grazing would have little significance. "While this is true, neverthe- 

 less the older seedlings must come from first-year seedlings, and the 

 chances for a crop of first-year seedlings to develop into trees is cer- 

 tainly decreased if a large proportion is destroyed by sheep during 

 the first season. The only published observations on this point are 

 those of Leiberg (14) ^ who, on the basis of examinations on the 

 Coconino Forest in 1904, concluded that sheep destroy a very large 

 proportion of the seedlings in their cotyledon stage, but that after 

 they are 3 or 4 years old the damage is relatively slight. The pres- 

 ent investigation and that of Hill both indicate that the damage 

 during the cotyledon stage is of less consequence than that which 

 occurs after this stage is passed. 



The large seedling crop of 1919 furnished the long awaited op- 

 portunity to observe the effect of grazing upon seedlings during their 

 first season. As the seedlings sprang up at the rate of from 10,000 

 to 200.000 per acre, the number surviving after allowing for normal 

 mortality insured an adequate basis for conclusions. In August, 

 1919. 46 plots aggregating 4.150 square feet were established along 

 a line beginning 2 miles east and extending 5 miles west of the 

 Fort Valley Experiment Station on range grazed by sheep, cattle, 

 and horses. Forty-four check plots aggregating 2,750 square feet 

 were established within inclosures grazed only by cattle and horses 

 or closed to all grazing. The results are given in Table 30. The 

 number of seedlings injured by grazing on typical sheep range 

 from August to the end of October of the first year varied from 

 8 to 23 per cent, with an average of 12 per cent for all groups of 

 plots under observation. Whenever a seedling was injured, almost 

 the entire crown was bitten off, killing the plant outright. To a 

 trained observer these decapitated stems are readily visible. At 

 the time the plots were established, right after germination, prac- 

 tically no damage was discernible, excepting in rare instances, as on 

 trails and bedding grounds. It is possible that seedlings in the early 

 stages may be completely destroyed, but after they are 3 or 4 weeks 

 old the roots are not pulled out by cattle or sheep, and therefore 



