48 



MISC. PUBLICATION 217, U. S. DEPT. OF AGRICULTURE 



Forest, and the combined area of the two national forests is 21,000,000 



acres. 



A very different type, known as the " interior" forest, lies mostly 

 within the drainage basins of the Yukon and Kuskokwim Rivers. 

 It is composed of small-sized trees of spruces, birches, and aspens and 

 other poplars which form dense stands over large areas. White 

 spruce is the only tree growing to saw-timber size. Trees which 

 occur in Alaska, but not in continental United States and therefore 

 not listed on pages 5 to 32, include the bigleaf willow (Salix ampli- 

 folia), feltleaf willow (S. alaxensis), Kenai birch (Betula kenaica), 

 Alaska white birch (B. neoalaskana) , and Alaska red birch (B. east- 

 woodae). This type of forest prevails over a vast area estimated at 

 some 80,000,000 acres (fig. 8). 



The prevailing trees of the two forest regions are: 



Coast forest: 



Western hemlock (important) 



Sitka spruce (important) . 



Western red cedar. 



Alaska cedar (yellow cedar). 



Mountain hemlock. 



Lodgepole pine. 



Black cottonwood. 



Red and Sitka alders. 



Willows. 



Interior forest: 



White (important) and black 



spruce. 

 Alaska white (important) and 



Kenai birches. 

 Black cottonwood. 

 Balsam poplar (Balm-of-Gilead) . 

 Aspen. 

 Willows. 

 Tamarack. 



FORESTS OF PUERTO RICO 



The forests of Puerto Rico are tropical and may be divided roughly 

 into wet forest, dry forest, and mangrove swamps, as shown in figure 

 9. These wet and dry forests are separated by the central mountain 

 range, which causes a heavy rainfall on the north-facing slopes and 

 a great shortage in precipitation on the south side in the southern 

 portion of the island. Forest vegetation culminates in density and 

 luxuriance of growth in the tropical rain forests of the northern and 

 central portions of the island (pi. 13). In the southern portion, the 

 lower mountain slopes, foothills, and coast lands are sparsely covered 

 with an open growth of short-bodied deciduous trees and shrubs. 

 The original forests of the island have largely disappeared through 

 clearing land for agriculture, heavy overcutting of timber, close 

 grazing, and burning. The second-growth forest, although irregular 

 in occurrence, consists of a great variety of species and forest types. 



The total forest area is reported to be about 100,000 acres, or about 

 5 percent of the total land surface, which originally was all in forest 

 growth. This is only one-fifteenth of an acre of forest land for each 

 inhabitant. Saw timber occurs on about 30,000 acres. The Caribbean 

 National Forest, with an area of about 14,000 acres and reaching a 

 climax in forest tree growth at an elevation of 2,000 feet, is being 

 managed on a conservative basis by the Forest Service. There are 

 some 37,000 acres of mangrove swamp of which about 15,000 acres 

 are in insular forest for protection of the coast. The principal forest 

 industry is burning charcoal. The island has no forest products for 

 export; on the other hand, it imports large quantities of lumber and 

 wood products. Only about 10,000 acres of virgin saw- timber forest 

 remain, located on the bottomlands and slopes of the mountains of 

 the national forest, and all rather difficult of access. 



