ALASKA FORESTS 243 



few inches below this cover is a bed of rock or ice or 

 frozen ground which thaws only for a foot or two in sum- 

 mer and prevents the water from sinking." The oppor- 

 tunities for tree seeds to sprout are, therefore, found only 

 here and there on the better drained slopes and on the 

 alluvial sands of river bottoms and islands. 



The lowlands which skirt Bering Sea and the Arctic 

 Ocean exhibit this inimical condition of soil, which is 

 sufficient to explain the absence of tree growth; but here 

 additional causes may be found in the absence of protec- 

 tion from the icy winter blasts, and perhaps in a defi- 

 ciency of summer rains, for, although the atmosphere is 

 humid, the low tundras furnish no causes for condensation. 



The peculiarity which seems in general to characterize 

 the Arctic flora, namely, the appearance of species in 

 groups or islands, attaches also to the forest cover, for the 

 forest is not always mixed, but groves of one species by 

 itself are frequent. Numerically the spruce would appear 

 the commonest, the birch the rarest tree. 



The economic importance of these limited forest areas 

 is growing with the development of the mining industry. 

 Not only must the scanty resources be drawn upon for 

 fuel to keep the houses warm, and to run the steamboats 

 and machinery, but the advantageous working of the 

 placers requires the use of fire in thawing the frozen 

 ground. Yet the usual carelessness and recklessness 

 which characterize pioneering has already shown itself 

 in the destruction of considerable areas by fire. It is said 

 that around Lake Lindeman, nearly all the timber is 

 burned off, none suitable for boat building being left. 



Lieutenant Allen reports burnt spruce in various lo- 

 calities and speaks of the " heavy smoke caused by the 

 extensive timber fires which obscured the sun the entire 

 day." In this case it was the signal fires of the Indians 

 which were the cause. 



