ASPEN AS A TEMPORARY FOREST TYPE 297 



Plantations Made in Spring of 1913 



Light intensity 25 .30. .45 .60 i.oo 



Species — Per cent living, fall of 1917 



Engelmann spruce 61 30 19 12 



Plantations Made in Spring of 1917 



Light intensity 09 .25 .30 .46 i.oo 



Species — Per cent living, fall of 1917 



Western yellow pine jz 78 81 67 50 



Douglas fir 68 55 60 44 55 



Norway spruce 93 84 67 55 35 



It will be observed that with the exception of the intolerant western 

 yellow pine, which does best under moderate shade, the greatest suc- 

 cess is correlated with the greatest aspen shade. Nevertheless, on the 

 part of the plantation where the light intensity is but .09 normal there 

 are a number of western yellow pines and Douglas firs from an ad- 

 ministrative planting made in 1909. The pines are spindling and poor, 

 but they still make good growth. The Douglas firs, on the other hand, 

 are thrifty. Since .09 full sunlight is practically the minimum intensity 

 under aspen, it appears from plantings that tolerant conifers can not 

 only exist, but can thrive under all aspen, as far as light may be con- 

 cerned. This fact has been noted elsewhere than at the Utah Experi- 

 ment Station. Pearson recommends aspen as an excellent nurse tree 

 in the mountains of Arizona and New Mexico'' under conditions simi- 

 lar to those found in the Great Basin. 



The natural reproduction shows up much the same as the planted 

 stock. In the dense aspen referred to above, natural white fir seedlings 

 are found at the rate of 86 per acre, and all appear to be doing well. 

 Another area covered with dense aspen showed no white fir and 

 Douglas fir seedlings per acre, all of which are thrifty, yet the light in- 

 tensity is only .105 of the full sunlight. 



The tolerance of native conifers is also shown on a permanent sam- 

 ple plot in first-class immature aspen. Here the aspen grew .38 inch 

 in diameter between 1910 and 191 5, while 20 alpine fir poles increased 

 1.69 inches. This indicates a condition far from suppression. The dif- 

 ference in heigiit growth doubtless would be even more striking if the 

 data were available. Nine per cent of the aspen on this plot died from 

 crowding during the last 5-year period, but all the alpine firs re- 

 mained healthy. It seems perfectly obvious, therefore, tliat aspen is 

 quite unable to withstand coniferous invasion. 



'Pearson, G. .'\. : "The Role of Aspen in the Reforestation of Mountain Burn> 

 in .Arizona and New Mexico." Plant World. \nl. 17, 240, September, 1014. 



