42 BULLETIX 1264, U. S. DEPAKTMENT OE AGKICULTTJRE. 



will permit. The conspicuous success of western yellow pine on 

 Douglas-fir burns may be cited as an example. In order to reduce 

 first-year losses to a minimum, it is also desirable to use stock with 

 (1) a well-balanced and extensive system of fibrous roots, (2) a 

 tendency to develop a new and deep root growth quickly, (3) a 

 relatively low transpiration rate in proportion to the absorption of 

 moisture, and (4) a high resistance to wilting through high sap 

 concentration. 



These losses may also be guarded against by planting where there 

 is a minimum amount of root competition with shallow-rooted 

 vegetation already well established on the area. Disastrous results 

 with western yellow pine on sagebrush sites have followed when this 

 factor was ignored. Another common example is afforded by the 

 complete failure of Engelmann spruce plantations on old spruce 

 burns which have grown up to a dense stand of grass. 



The density of the cover is charged with the failure of about 10 per 

 cent of the administrative plantations and should always be considered 

 in connection with the quality of the planting site. Although rarely 

 responsible for the immediate extermination of plantations, the effect 

 is cumulative and becomes successively more pronounced with the 

 increasing age of the plantations. Since dining the first season in the 

 field much of the development of the plant is dependent upon stored 

 food materials that were formed under the ideal conditions of the 

 nursery, heavy cover at this time, shading the ground and thus pre- 

 venting excessive water loss from the plant and the rapid drying out 

 of the soil, rather encourages survival and growth. After the first 

 year the plant is dependent upon its new habitat. Having become 

 established by one year's field growth, sudden death is unlikely; but 

 growth may become subnormal, with the result that the plant dwin- 

 dles slowly away. 



Snow-molding fungi are frequently dangerous on sites having too 

 heavy cover and are often the direct cause of death. Then, too, 

 species which are intolerant in youth naturally suffer most from too 

 dense shade; western yellow pine, lodgepole pine, and blue spruce 

 being frequently weakened and killed from this cause. Oak brush 

 of maximum density and dense aspen are too dark for the general 

 success of western yellow pine. Dense aspen leads also to failure of 

 lodgepole pine and even when of only moderate density frequently 

 reduces thrift. Blue spruce slowly fails under dense aspen and 

 herbaceous cover (such as Rudbeckia occidentalis), and under all aspen 

 stands with thick undergrowth. 



It is evident that in order to insure the best success, sites selected 

 for planting must have an ample supply of soil moisture during the 

 growing season, proper shade, a fairly open, porous soil of high water 

 supplying power and not chemically unfavorable. 



RODENTS. 



Rodents come next to unfavorable sites in responsibility for planta- 

 tion failures, being charged with nearly one-fourth of the losses on 

 administrative plantings. These animals, chiefly the snowshoe 

 rabbit (Lepus americanus), gophers, and ground squirrels, are very 

 destructive, particularly in new plantations established in localities 

 distant from natural coniferous growth. 



