72 BULLETIN 700, U. S. DEPARTMENT OF AGRICULTURE. 



continue to be of high value in the pasturing of live stock. On the 

 more favorable sites from the oak-brush up to and including the 

 spruce-fir association, lands which have been overgrazed and are not 

 fully stocked with vegetation may be increased in forage production 

 by the seeding of suitable plants, preferably native species. 1 



Since evaporation is apparently the chief factor limiting growth 

 and development of plants in the oak-brush and spruce-fir types, 

 the extension of agriculture and forestry should be limited to lands 

 protected from excessive evaporation. This may be done by select- 

 ing sites that are more or less protected by native vegetation and 

 natural obstacles. Failures in experimental plantings, in most in- 

 stances, have occurred on wind-swept lands where the soil moisture 

 becomes deficient early in the season. In the selection of species, 

 either of herbaceous or of woody plants, only the most drought re- 

 sistant sorts should be used. Failures in the case of the planting of 

 suitable timber species in the central (aspen-fir) type will probably 

 seldom be caused by adverse climatic conditions. Failures in this 

 type may generally be traced to the employment of unsuitable stock, 

 or to bad workmanship, wrong season of planting, or other pre- 

 ventable causes. 



1 Sampson, Arthur W. Natural revegetation of range lands based upon growth re- 

 quirements and life history of the vegetation. Journ. of Agr. Research, Vol. Ill, No. 2, 

 1914. 



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