THE COAST FORESTS 139 



There remains less than one third of the land area, 27 per cent 

 to be exact. Of this 6 per cent is capable of producing large 

 sized saw. timber. It is confined to southwestern Alaska whose 

 chmate has already been described. The remainder of the timber 

 producing area, 21 per cent of the whole territory, has, however, 

 an entirely different climate. The conditions at Fairbanks in the 

 Yukon Valley may be taken as typical of this region. The mean 

 annual precipitation is 15 inches. The winters are long and cold 

 while the' summers tho short are warm. July, for example, has 

 an average of 57° F. Furthermore, there is almost continual day- 

 light during the vegetative season. Consequently the upper 

 surface of the soil thaws out sufficiently to permit vegetative 

 growth while the frozen layers beneath supply ample moisture by 

 capillary attraction. There results, therefore, rapid growth in 

 spite of the short season and scant rainfall. White spruce (Picea 

 canadensis) and three cottonwoods (Populus balsamifera, tricho- 

 carpa and tremuloides) and white birch (Betula alaskana) are the 

 dominant species with black spruce (Picea nigra) and tamarack 

 (Larix alaskensis) much less common. These trees reach their 

 best development in the deep soiled river bottoms and are short 

 and stunted on the hillsides. Diameters of more than 18 inches 

 breast-high and total heights of over 50 feet are rare. The stands 

 are relatively open so that the yields per acre are not large. In 

 fact the wonder is that trees do so well rather than that they are 

 not larger and denser. Scant rain!fall and a long winter are only 

 partially offset by the long summer days and abundant supply 

 of ground moisture. 



The Coast Forests. — By contrast with the interior forests the 

 coast timber seems magnificent. It is in fact a northern exten- 

 sion of the luxuriant Douglas fir type of Washington and Oregon. 

 The composition is, however, considerably altered by the lower 

 temperatures. Douglas fir is no longer found but the dominant 

 species are western hemlock (Tsuga heterophylla) and Sitka 

 spruce (Picea sitchensis). Western red cedar (Thuya plicata) 

 and yellow cedar (Chamaecyparis Nootkatensis) occur sparingly 

 in southwestern Alaska. Species of little commercial importance 

 which are more or less abundant in this type are: 



