18 



THE FORESTS OF ALASKA. 



spruce rarely attains a diameter of 6 inches, and the less abundant 

 tamarack is even smaller. The best white-spruce trees are about 75 

 feet high. Birch, aspen, and poplar usually reach a height of about 

 50 feet; black spruce rarely more than 40 feet, many times not ex- 

 ceeding 20 feet, and tamarack seldom more than 30 feet. Naturally, 

 it is impossible for timber to grow rapidly or to large sizes in soil 

 which is perpetually frozen. On such sites the roots can penetrate 

 only the overlying cover of moss and humus and must spread out flat 

 upon the frozen layer beneath. Rapid and thrifty growth has taken 

 place only upon warm slopes and in river valleys with sandy soil, 

 where the roots are able to go deeper. 



The following detailed notes upon the rate of growth of white 

 spruce and white birch were secured. It was very difficult to count 

 the rings on white birch, and in some cases it was practically impos- 

 sible to calculate them closer than to the nearest ten. Ring counts on 

 white-spruce stumps, which had grown under favorable conditions 

 on Minook Creek above Rampart, are given in Table 1. 



Table 1. — Diameter growth of white spruce, as shown bg ring counts on stumps, 



with averages. 



Height. 



Diameter 

 outside 

 bark. 



Rings. 



Height. 



Diameter 

 outside 

 bark. 



Rings. 



Height. 



Diameter 

 outside 

 bark. 



Rings. 



Inches. 

 24 

 22 



--- 2 'i" 



Inches. 



12.5 



7.5 



11.0 



8.0 



Number. 

 125 

 150 

 140 

 140 



Inches. 

 20 

 12 

 12 

 24 



Inches. 

 7.5 

 G.O 

 11.5 

 14.0 



Nu mber. 

 170 

 170 

 140 

 140 



Inches. 

 16 

 16 



Inches. 

 12.5 

 12.5 



Number. 

 140 

 140 



19 



10.3 



146 



Table 2 gives similar information on white spruce. The measure- 

 ments were made on logs at a Fairbanks mill. 



Table 2. — Diameter and height growth of white spruce, as shown bg ring counts 

 on saw logs, with averages. 



Butt. 



Length. 



Top. 



Bl 



tt. 



Length. 



Top. 



Diameter 





Diameter 





Diameter 





Diameter 





outside 



Rings. 





outside 



Rings. 



outside 



Rings. 





outside 



Rings. 



bark. 







bark. 





bark. 







bark. 





Inches. 



Number. 



Feet. 



Inches. 



Number. 



Inches. 



Number. 



Feet. 



Inches. 



Number. 



17.0 



167 



37.2 



11.0 



108 



17.0 



198 



33.7 



11.9 



130 



16.4 



155 



33.3 



11.3 



110 



18.4 



168 



32.6 



11.5 



114 



15.6 



110 



35.1 



11.0 



70 



16.1 



146 



33.0 



11.0 



120 



17.3 



150 



25.0 



13.2 



100 



15.4 



150 



32.7 



11.1 



no 



18.8 



198 



35.7 



12.0 



130 



14.8 



110 



32.5 



10.3 



88 



16.0 



136 



33.1 



11.2 



110 



17.0 



124 



28.3 



11.0 



85 



16.1 



118 



30.5 



12.1 



93 



16.0 



90 



30.6 



12.2 



78 



15.0 



140 



32.9 



11.2 



100 



17.2 



120 



33.0 



11.1 



80 



14.7 



100 



30.5 



11.6 



75 



15.8 



117 



32.8 



11.1 



80 



15.4 



200 



32.8 



10.5 



160 



15.7 



97 



31.7 



10.2 



68 



19.0 



116 



32.7 



10.6 



80 



16.0 



155 



33.0 



11.5 



125 



17.0 

 16.2 



190 

 200 



35.3 

 35.7 



11.3 

 11.8 



160 

 137 













16.4 



143 



32.6 



11.3 



104 



15.5 



120 



30.7 



11.3 



83 













