ASPEN AS A PERMANENT FOREST TYPE 759 



ments at the Utah Experiment Station, in a few years the area restocks 

 with a dense jungle in which the writer would hesitate to introduce the 

 slow-growing conifers for fear that they would be smothered. In fact, 

 heavy stands when underplanted there with conifers have to be thinned. 

 Some years ago the writer had occasion to clear aspen-covered land for 

 a nursery site, when the whole stand was found to be connected by 

 superficial roots in which the smaller trees were joined to the next 

 larger, and so on up the line. This proved the sprout origin of the 

 stand. Throughout the district one repeatedly observes at time of 

 flowering or leafing out that the staminate and pistillate trees occur in 

 pure groups and patches, which would not be the case if the stands 

 originated from seed. By virtue of this capacity for reproducing from 

 root sprouts, aspen is practically independent of seed, and has this de- 

 cided advantage over the conifers, whose seed occurs at irregular inter- 

 vals, is eagerly sought by birds and rodents, becomes subject to drought 

 before, during, and after germination, and to diseases, and is handi- 

 capped by slow initial growth. 



Moreover, aspen leaves and litter harbor a fungus of the cobweb 

 type, known either as Herpotrichia or Botrytis, which weakens and 

 kills small conifers during winters in which the snowfall is very heavy. 

 This afifects natural seedlings as well as those resulting from direct 

 seeding or planting. Aspen foliage may be a good shelter for such 

 species as Douglas fir and Engelmann spruce during the hot summer 

 months, but may become an agency for their destruction in winter or 

 early spring. If we were to mulch our first-year nursery beds in au- 

 tumn with a normal fall of leaves from a good stand of aspen, the 

 chances are that all of the seedlings would be dead in spring. 



Snow-shoe rabbits generally abound in the pure aspen as well as in 

 the mixed and pure conifer types, but their influence is most keenly 

 felt where the conifers are the scarcest. Thus, where the mixed type 

 is approached, the few conifers that sift in and struggle along are fre- 

 quently pruned back annually on top of the snow until they finally get 

 above reach or, what is just as likely, until they succumb entirely. In 

 case of plantations made in the pure aspen type, this drain upon the 

 conifer supply becomes especially heavy and indicates what happens to 

 natural seedlings that may get started and reach the attractive stage. 



Whether attributed to drought, fungi, heavy shade, leaf cover, rab- 

 bits, or to the unfavorable site, the fact remains that the great majority 

 of the plantations made in the type of aspen which the writer classes' 

 as permanent, even though successful for a while, eventually played 

 out or died a lingering death, which argues against a natural rotation 

 with the native species used. 



