62 BULLETIN 790, U. S. DEPARTMENT OF AGRICULTURE. 



The foregoing example applies to range where the soil still retains 

 most of its original fertility and where there is still considerable 

 of the original perennial vegetation. If the range has deteriorated 

 beyond this stage, more than two years of deferred grazing on each 

 third of the range will be necessary for revegetatiom and the rotation 

 will extend oyer a longer period. The number of years necessary or 

 the number advisable depends upon the extent to which the vegeta- 

 tion has been killed out and ih& soil depleted in fertility x and must 

 be decided in the individual case after a careful examination of the 

 vegetation. Deferred grazing should be continued until there is sat- 

 isfactory reproduction of the principal forage species. 



Of course, there are difficulties to overcome in the application of 

 deferred and rotation grazing, but in only a very few cases is it im- 

 possible to work out and eventually apply a plan which will aid in 

 maintaining the vigor and productiveness of the main forage plants 

 and occasionally allow the production of a seed crop. On ranges 

 within the National Forests the two main difficulties are: (1) Great 

 variation in character of forage and growing season, due to varia- 

 tion in altitude and exposure: (2) lack of fences or other means 

 of controlling the stock, especially cattle. 



The division of range into spring grazing extending up to about 

 July 1 and summer grazing" from July 1 on, as suggested in the dis- 

 cussion of seasonal grazing, will in part overcome the difficulty of 

 variation in growing season. The growing season throughout the 

 range set aside for spring grazing will ordinarily be uniform enough 

 to admit of a plan for deferred grazing to meet the needs of this 

 range. Likewise, the growing season on the range opened to use 

 about July 1 will be sufficiently uniform to make possible a sub- 

 division for deferred grazing along the lines of the sample plan 

 given. This division into spring and summer grazing has been made 

 on parts of the range on many National Forests, especially on the 

 sheep range. And in many instances deferred and rotation grazing 

 has been applied in the way shown in figure 4. Eventually there 

 must be some such division on most of the cattle ranges, with corre- 

 sponding control of the cattle to prevent premature grazing" of the 

 higher range in certain cases and in others to prevent seasoniong 

 grazing and overstocking of the range at the lower altitude-. 



The variation in season of growth between the Forest boundary 

 and the mountain top and high basins is so great that inclusion of the 



1 Sampson, Arthur W., Natural Revegetation of Range Lands Based upon Growth 

 Requirements and Life History of the Vegetation. U. S. Dept. of Agriculture, Journal 

 Agricultural Research, Vol. Ill, No. 2, pp. 93-147, Nov. 16, 1914. 



Sampson, Arthur W., and Weyl, L. H., Range> Preservation and its Relation to Erosion 

 Control on Western Grazing Lands. U. S. Dept. of Agriculture, Bui. G73, 1918. 



Sampson, Arthur W., Plant Succession in Relation to Range Management. U. S. Dopt. 

 of Agriculture, Bui. 791, 1919. 



