EFFECT OF GRAZING UPON" ASPEN REPRODUCTION". 25 



tops to cover effectively the entire ground surface and thus prevent 

 the entrance of stock, the method permits the establishment of a 

 fairly good stand of vigorous, well-formed trees. 



Observations covering a five-year period have made it evident that 

 the tops of aspen scattered over a clear-cutting in such a manner as 

 to protect the sprouts are well along in decay in the third year after 

 scattering; and usually by the end of the fifth year only the central 

 axis of the top remains, this portion often being pretty thoroughly 

 decayed. The absence of turpentine and other volatile and highly 

 inflammable oils, couple'd with the relatively high precipitation in the 

 aspen type and the tendency of the species to absorb and retain a 

 large percentage of moisture when lying on the ground, makes the 

 fire risk due to the scattering of the brush practically negligible. 



Another means of protecting the sprouts from browsing is to pile 

 the tops in windrows, as it were, thereby fencing out the stock during 

 the period required for partial decay of the nonmerchantable parts 

 This method, however, is not particularly applicable to field opera- 

 tions, and instead of fostering the sprouts by protecting them from 

 frost, the sun's excessive heat, evaporation, and other adverse factors, 

 exposes the reproduction to the elements in much the same way as 

 when the brush is piled and burned. 



SUMMARY. 



(1) Aspen, a tree of high commercial value on many National For- 

 ests in the West and on some of the farm woodlots and lands adjacent 

 thereto in northeastern United States, is often reproduced with diffi- 

 culty where the lands are made to serve the double purpose of timber 

 and meat production. 



(2) The leafage, young twigs, and branches of the reproduction 

 are browsed with varying degrees of relish by both cattle and sheep. 

 Over 90 per cent of the damage inflicted by stock is chargeable to 

 browsing, the injury due to trampling, rubbing, and similar causes 

 being negligible. 



(3) Sheep are responsible for severe damage to the reproduction, 

 both as it occurs in standing timber and on clear cuttings, regardless 

 of the variety and supply of choice forage. Cattle cause some damage, 

 but the extent of injury is usually slight, except where the lands are 

 overgrazed or where the animals are inclined to congregate for more 

 or less lengthy periods. 



(4) The injury and mortality chargeable to the presence of live 

 stock is roughly proportional to the closeness to which the lands are 

 grazed. Observations covering a 5-year period in standing timber 

 on sheep range showed that 27.2 per cent of the reproduction was 

 either injured or killed on lightly grazed plots, 31.8 per cent on mod- 

 erately grazed areas, and 65 per cent on heavily grazed plots. A 



