EFFECT OF GEAZING UPON ASPEN REPRODUCTION. 17 



questionable value. Reproduction, on clear-cut lands located on 

 cattle range, on the other hand, while damaged more or less by- 

 browsing, appears to occur in sufficient density over the plots under 

 observation to insure a maximum stand of first quality mature timber. 



Practically without exception there are no young aspen sprouts 

 on range grazed annually by sheep during the period that the sprouts 

 are being produced. The few sprouts found are almost invariably 

 lacking in vigor and are often more or less seriously diseased. On the 

 range used exclusively by cattle it is the exception not to find at least 

 a partial stand of sprouts varying in age, most of which are vigorous 

 and healthy. Cattle naturally prefer the leafage of herbs, especially 

 grasses, to shrubs and other woody plants, and while they browse 

 aspen reproduction, the damage they do seldom endangers the per- 

 manent establishment of the stand unless the range is stocked with 

 cattle beyond its natural carrying capacity. 



An analysis of the character of the injuries showed that the pro- 

 portion of terminal and lateral shoots browsed was practically the 

 same on cattle and on sheep allotments. It was quite evident, 

 however, that the cattle browsed the foliage more and the woody 

 tissue less than sheep; consequently the complete removal of ter- 

 minal and lateral shoots was less commonly observed on the cattle 

 ranges than on the sheep ranges. The difference would appear to 

 account for the more rapid and complete recovery of injured sprouts 

 on cattle allotments. 



Practically no damage is caused to aspen reproduction by rubbing 

 and trampling by cattle. Rubbing is generally confined to young 

 conifer saplings characteristically scattered through the aspen type, 

 the needles and bark of which afford the friction desired, or to aspen 

 specimens of about pole size. Young aspen sprouts are so limber that 

 stock seldom break the branches or otherwise distort them by rubbing. 

 Sheep, of course, not being addicted to the rubbing habit like cattle, 

 cause virtually no damage in this way. Trampling by either class 

 of stock causes very slight mortality or permanent injury. On sheep 

 ranges the young sprouts are either killed or seriously damaged long 

 before the formation of prominent trails which might otherwise 

 result in trampling out the reproduction. On cattle allotments there 

 is occasionally a small amount of damage to young sprouts by tram- 

 pling, portions of the bark being removed along the main stem or 

 the specimen being broken; but such injury is negligible on lands 

 stocked according to their actual carrying capacity and on which the 

 animals are properly distributed. Where cattle have a tendency to 

 congregate, however, near watering and salting places, for instance, 

 both browsing and trampling have a telling effect on the density and 

 vigor of the reproduction. 



