REGULATION OF GRAZING 369 



1. Amount of injury: "The damage to seedlings more than a year old was 

 negligible in quantity" ; a yearly average of about 2.8 per cent. 



Of seedlings less than one year old an average of 15.4 per cent on the Dead- 

 wood area and 24.9 per cent on Silver Creek were killed. 



These figures, according to Sparhawk, represent the damage on grazed plots 

 on,ly, and indicate "the maximum loss which would result if the sheep grazed 

 over every square yard of their allotment." He points out "that an area is 

 seldom grazed so closely unless it is much overstocked ; a great many spots are 

 missed, and many of them are likely to be patches of reproduction, since there 

 is usually little palatable forage in such places." 



Of the tota^l seedlings over one year of age on all plots, both grazed and un- 

 grazed, 1.1 per cent were killed each year on the Deadwood range, which was 

 lightly grazed, and 2.5 per cent on closely grazed Silver Creek range. 



Of seedlings less than 1 year of age, on all plots, 8.8 per cent on Deadwood 

 and 14.8 per cent on Silver Creek were killed each year. 



Computations based upon the annuaj data collected show that about 45 per 

 cent of the western yellow pine which germinates will eventually be killed if 

 the area is grazed completely every year; or about 7.2 per cent will be killed if 

 grazing is eliminated untij the seedlings pass the third year of age. 



"During the first few years seedlings succumb very easily to slight injuries, 

 because of their small size, shallow root system, and the lack of woody matter 

 in their stems. The loss due to grazing decreased from about 2U per cent for 

 seedlings in their first year to 11 per cent for those in their second and third 

 years. By the end of the third year they are from 2 to 4 inches high (depend- 

 ing on species and site), their stems have become woody and fairly tough, and 

 their roots penetrate the soil for a foot or more, so that they are not easily up- 

 rooted by trampling nor exposed to drying by the loosening of the soil. Injury 

 from grazing is so slight after this that there is no need for closing reproduc- 

 tion areas to sheep after the third year, though it may be desirable to graze 

 such areas lightly for a few years more, until the seedlings reach a height of 

 6 inches." 



2. Season of injury: "The proportion of seedlings killed by grazing, par- 

 ticularly of those less than a year old, was very much greater early in the sea- 

 son than it was later. The reasons for this are that early in summer the seed- 

 lings are rather brittle, with little wood in their stems ; their roots do not go 

 down very deep ; the soil is moist and easily shoved out of place by the sheep ; 

 and seedlings injured early are either kijled outright or have small chance to 

 recover because of the dry period which follows the injury. By the middle of 

 August the season's growth is nearly completed, the stems are tougher, the 

 roots deeper and more widely spread, the soil is more firmly packed, and an 

 injury is soon followed by the fall rainy period and the long winter period of 

 rest, so that there is a fair chance for recovery from slight disturbanee." 



2. Relation bctivccn amount or damage and intensity of gracing: "As would 

 be expected, the amount of injury and death increased fairly constantly with in- 

 creased intensity of grazing. Except on bed grounds and areas grazed with 

 similar intensity, the damage was not very serious for seedlings more than a 

 year old, and even in such places only 4 per cent of the seedlings were killed. 



