140 BULLETIN 1105, U. S. DEPARTMENT OF AGRICULTURE. 



saplings creates a fire menace. It also covers up and kills many of 

 the smaller seedlings. 



GRAZING. 



Improper sheep grazing is at present the largest controllable 

 obstacle to reproduction of western yellow pine on the NationaL 

 Forests of the Southwest. Under the methods of cutting practiced 

 by the Forest Service, reproduction is reasonably certain if exces- 

 sive damage by grazing is avoided; but unless this damage is rig- 

 idly controlled failure may be expected, regardless of method of 

 cutting or other silvicultural measures. Instances in which good 

 reproduction has taken place under uncontrolled grazing on private 

 lands. or on Government lands before they were placed under For- 

 est Service administration may be explained by the occurrence of 

 unusually favorable climatic conditions, which enable seedlings to 

 start in large numbers, or by the fortuitous absence of such grazing 

 conditions as tend to bring about excessive damage. 



Under normal conditions cattle and horses do a relatively small 

 amount of damage, but on areas which are overstocked or which for 

 other reasons supply too little feed for the animals present, cattle 

 and horses may injure a high percentage of the seedlings. The 

 same factors determine to a large extent the amount of damage by 

 sheep. But it can not be said with certainty that under normal 

 grazing conditions sheep will not do excessive damage. Sheep 

 browse yellow-pine seedlings to a considerable extent under normal 

 conditions in the Southwest. Whether the damage falls within the 

 limits permissible from the standpoint of silviculture depends upon 

 a number of circumstances. If pine seedlings spring up in great 

 abundance and at frequent intervals, large losses might be sustained 

 without serious consequences, whereas if reproduction occurs spar- 

 ingly the same amount of damage would be disastrous. Undoubt- 

 edly the intensity of grazing, the amount of palatable forage avail- 

 able for each class of stock, and methods of handling are important 

 factors in the sheep problem ; but until it is known more definitely 

 how much weight to give these and other factors, sheep grazing must 

 be regarded as a serious deterrent to the reproduction of western 

 yellow pine in this region. 



Until it is demonstrated that grazing management can effectively 

 assure reproduction, sheep should be kept off areas which are in 

 process of restocking until most of the seedlings are about 3 feet 

 high. Under average conditions this will require approximately 20 

 years. Eeproduction can be hastened and the period of exclusion 

 shortened correspondingly by removing sheep about 10 years before 

 cutting, thus taking advantage of the prolific seeding of virgin 

 stands. 



