18 



BULLETIN 580, IT. S. DEPARTMENT OF AGRICULTURE. 



BENEFICIAL EFFECTS. 



Probably the only important ways in which stock aid in the 

 establishment of reproduction are by helping to plant the seeds and 

 by reducing the fire menace. 



Sheep aid very materially in covering the seeds of grasses, thus 

 helping to insure their germination. 1 It is reasonable to suppose 

 that they aid in planting the seed of yellow pine. However, this aid 

 is not very important, because the important problem in establishing 

 a stand of reproduction is not to secure germination but to resist 

 freezing during the following winter and starvation during the 

 long dry period of the following spring. 



Grazing, by preventing the accumulation of rank growth, plays 

 no small part in preventing severe ground fires. 



HEIGHT GROWTH. 



The extent to which the growth of young trees is retarded forms 

 the most obvious index of the severity of the" effects of grazing 

 injuries. The effects upon height growth, however, indicate the 

 immediate results of injuries and may or may not be a guide to the 

 more permanent effects. 



On Taylor's ranch, 9 miles northwest of Flagstaff, is a pasture 

 in which the reproduction is abundant and free from injury. Just 

 outside of the pasture damage by grazing has been very severe. 

 Measurements of the height growth of saplings for the last five years 

 within and outside the pasture gave the results shown in Table VII. 

 Twenty trees form the basis for each height class. 



Table VII. — Comparison of Jieight growth of trees in and outside of pasture. 



Height 

 class. 



Growth, of the av- 

 erage tree dur- 

 ing last 5 years. 



In 

 pasture. 



Outside 



of 

 pasture. 



Feet. 



1 

 2 

 3 

 4 



Feet. 

 1.02 

 1.45 

 1.97 

 2.53 



Feet. 



0.6 



84 



97 



1.26 



The growth outside of the pasture is scarcely more than 50 per 

 cent of that inside. 



Measurements of 75 representative trees selected from three of the 

 inclosures fenced in connection with this project in 1912 revealed an 



1 Journal of Agricultural Research, Department of Agriculture, Vol. III. No. 2, " Natu- 

 ral Revegetation of Range Lands Based upon Growth Requirements and Life History of 

 the Vegetation," by Arthur W. Sampson. 



