240 THE FUTURE OF ARID LANDS 
offset the cost, and some research is being done to develop products 
such as pulp for paper, chemical extractives, and others. For the 
comparatively level lands where shrub and tree control is now 
practiced, the change to grasses is desirable for both forage pro- 
duction and erosion control provided that grazing is carefully 
managed. In the shrub and woodland zone, erosion is often active 
because of insufficient effective grass cover to protect the soil. 
Unless the increased growth of trees and shrubs is reduced, grass 
cover cannot be increased because the roots of woody plants domi- 
nate even the open areas and extract available soil moisture. The 
necessity for proper control of grazing after brush is removed 
must be emphasized. 
Management of Higher Forested Areas in Arid Regions 
At higher elevations, the mountain ranges and plateaus are 
covered with valuable forests of tall pines (Pinus spp.), spruces 
(Picea spp.), and firs (4dzes spp.). 
Thinning and improvement cutting in the ponderosa pine, 
(Pinus ponderosa Laws.) and spruce-fir forests do not present 
erosion hazards in themselves. The danger of erosion comes from 
the skid trails and logging roads built and used to remove the prod- 
ucts. In thinning, the general recommendation is to remove the 
slowest growing trees to concentrate the capacity of the site upon 
the most vigorous trees. When stands are mature or overmature, 
as in much of the spruce-fir zone, harvest cuttings are made to 
replace the slow-growing old trees with young fast-growing 
trees (5). 
To prevent excessive erosion, roads must be carefully located 
to avoid steep pitches and soils that erode easily. Drainage must 
be provided to prevent water from concentrating on the road sur- 
face and in side ditches. Cuts, and particularly fill banks, must be 
protected. Much of the high country is too steep to be logged by 
methods now in common use without excessive erosion. For these 
locations, cable logging, chutes, or other methods are needed for 
transporting logs with less road building (16). 
Improvements in utilization and the development of new mar- 
kets for wood products will make possible better management to 
