44 MISC. PUBLICATION 217, U. S. DEFT. OF AGRICULTURE 



Many are relatively small timbered tracts, lying on the ridges and 

 higher mountain plateaus, interspersed with great treeless stretches 

 and sometimes widely scattered in large arid districts, as in parts of 

 Nevada, Utah, and Arizona, As a result, the timber is locally in 

 good demand and valuable for development, as well as for shipping 

 to other points. 



The change in forest cover as one ascends a mountain slope may be 

 illustrated by the successive belts in the southern Colorado-New 

 Mexico forest area. First, at altitudes ranging from 5,000 feet on 

 moister situations to 6,000 feet on drier slopes occurs a belt of one- 

 seeded, alligator, or Utah junipers and pinon, or nut pine; above it 

 ponderosa (western yellow) pine which forms extensive forests over 

 the highly dissected Colorado plateau; with Douglas fir and white fir 

 mingling in the stand in the upper part of the belt, and often so pre- 

 dominating as to form pure stands at 8,000 feet; and finally Engel- 

 mann spruce over an extensive horizontal belt terminating at the 

 upper portion at altitudes of 9,000 to 11,000 feet in a belt of alpine fir. 



In the northern Montana-Idaho portion of the Rocky Mountain 

 region, forest growth begins at elevations of 3,000 to 4,000 feet 

 and, depending very much upon the exposure and soil moisture, ex- 

 tends upward to 6,500 to 7,000 feet. Limber and western white pine 

 blend at 4,500 feet. The maximum commercial forest growth occurs 

 at about 5,000 feet with limber pine on the dry southern exposures and 

 on the moister or northern slopes Engelmann spruce and alpine fir. 

 Another important tree in the central portion of the region is lodgepole 

 pine, a tall slender tree which grows in dense stands, deriving its name 

 from its use by Indians in making lodges or tepees. 



The total area of the many separate divisions or blocks of the Rocky 

 Mountain region amounts to about 62,899,000 acres, or about 13 

 percent of the total forest land in the United States. The most 

 extensive type is the ponderosa (western yellow) pine, occupying 

 21,811,000 acres, or about 35 percent of the region. The lodgepole 

 pine type covers about 26 percent or 16,541,000 acres, the western 

 white pine-western larch type about 21 percent or 12,984,000 acres, 

 and the Douglas fir and Engelmann spruce (with some others) about 

 18 percent or 11,563,000 acres. 



The present condition of the Rocky Mountain region is to a very 

 large degree the result of extensive fires set by prospectors in search 

 for outcroppings of gold, silver, or copper ores, over much of the 

 period since the early fifties, and those set by other early pioneers 

 and by tourists who came later. In an earlier day, the Spaniards 

 and their descendants regularly burned over the mountains to get rid 

 of the forest and in its place provide forage for their goats and sheep. 

 Lumbering has been carried on, on a varying scale, as markets have 

 been available during the past 60 years or so, both locally and over the 

 treeless agricultural region to the east. 



An idea of the composition of the forest in the various parts of the 

 Rocky Mountain region can be gained from the grouping of the trees 

 in the order of their relative importance for each of the northern, 

 central, and southern portions, as follows: 



