16 BULLETIN 580, U. S. DEPARTMENT OF AGRICULTURE. 



Counts were made on IT plots located in situations subject to this 

 kind of injury. Of 165 trees above 3 feet in height, and so of a size 

 subject to severe damage by rubbing, 36 were seriously injured. Fif- 

 teen were so badly rubbed that they would become worthless if the 

 rubbing continued, and 2 were moderately rubbed. Thus 22 per 

 cent of the trees subject to this class of damage had been severely in- 

 jured, and 9 per cent were being subjected to severe damage. In all, 

 a total of 31 per cent would in time be killed. This indicates a seri- 

 ous condition over certain parts of the yellow-pine type. The sites 

 on which such damage is most likely to occur support the best quality 

 of timber. 



Damage along sheep driveways. — In the southern part of the Forest 

 the only places where pine reproduction seems to be injured are 

 around watering places, near the lower boundary of the yellow-pine 

 type where reproduction is scattered, and along the Mud Tank sheep 

 driveway. This driveway, with an average depth of 1 mile, extends 

 about 30 miles through the yellow-pine type. About 75,000 sheep 

 are driven over it each year. Besides its use as a driveway, the strip 

 is included in sheep and cattle allotments, and would be fairly well 

 grazed by stock throughout the season without the additional use by 

 transient stock. The first few bands find sufficient feed, but before 

 the total number have crossed the feed is so short that sheep are 

 forced to eat whatever growth is available, including a great deal of 

 yellow-pine reproduction. The damage caused in this way is so 

 severe that the boundaries of the driveway can readily be traced by 

 the line of severe damage. Conditions on this trail are typical of a 

 number of trails in Arizona and New Mexico. Good management re- 

 quires that this damage be reduced to the minimum. 



Around watering places and ranches where stock are allowed to 

 congregate it is very common to find a majority of the reproduction 

 badly deformed and stunted, as a result of browsing and rubbing. 



EFFECTS OF GRAZING INJURIES UPON WESTERN YELLOW-PINE 



REPRODUCTION. 



ESTABLISHMENT OF REPRODUCTION. 



INJURIOUS EFFECTS. 



Abundant reproduction is often found in pastures, while just out- 

 side, with no apparent change in natural conditions, it is relatively 

 scarce. In all such cases observed the outside range had been subject 

 to severe grazing bv all classes of stock for a number of vears after 

 the pasture had been constructed. A comparison of the ages of 

 reproduction within and those adjacent to the pastures indicates that 

 the effect of severe grazing outside has been not only to prevent the 

 establishment of reproduction, but also to kill many of the trees 

 alreadv established at the time the fences were built. This conclu- 



