PLANT SUCCESSION- AND RANGE MANAGEMENT. 63 
distinctly in favor of the protected plot. Thus, for instance, yarrow 
shows a difference of 38 per cent in favor of the protected plot; 
slender wheat grass, 12 per cent; sweet sage, 100 per cent; small 
mountain porcupine grass, 63 per cent; and dandelion, 51 per cent. 
In four species the greatest density occurs on the unprotected area. 
In the case of at least one plant, tall larkspur, the result is apparently 
accidental, as the plants concerned are old and thoroughly estab- 
lished, so that it is not probable that they have invaded the area 
since the establishment of the plot. Two of the species, plantain 
and tansy mustard, rapidly colonize the more exposed soils, so that 
their greater rate of increment on the outside range, as compared 
with that on the better vegetated protected area, is not alogether 
surprising. 
The contrast in the relative height growth of the different species 
is strikingly in favor of the protected area, the percentages being 
greater in all but one instance. The exception is meadow rue, a 
plant which locally is grazed practically not at all, hence is as vigor- 
ous physiologically on the unprotected area as on the protected plot. 
Careful analysis of the data as to relative height shows that the per- 
centage difference is roughly in proportion to the palatability of the 
plant, as would be expected. According to observations, the differ- 
ence in height growth corresponds in general to the difference in seed 
production, the larger seed crop being produced on the protected 
urea. This physiological response, as a result of complete rest of a 
cover weakened by injudicious grazing, is identical with the vigorous 
response of a similarly weakened vegetation when the deferred and 
rotation system of grazing is applied. 1 In either treatment prac- 
tically complete physiological recovery results in about three years. 
1 Where a good deal of the original forage cover has been destroyed and the remaining 
plants weakened from overstocking or too early grazing, the deferred and rotation grazing 
system, if strictly applied, will soon result in revegetation. 
In applying the deferred system of grazing, such portion of the range as is consistent 
with the welfare of the range as a whole is reserved for cropping until after the ma- 
turity of the seed of the main forage species. Upon the maturity of the seed, the range 
is grazed closely, but not destructively, by the stock allotted to the lands. The follow- 
ing year, owing to the large proportion of seedlings destroyed, especially on areas grazed 
early in the season, the forage is not to be cropped until another season's seed has been 
produced. If, after the production of two seed crops of the choice native forage species, 
an ample number of seedling plants have been established, a second area in need of seed- 
ing is selected, and the tract upon which grazing was previously deferred is then grazed 
before seed maturity. This same plan is continued season after season, alternating the 
deferred grazing first on the one area and then on another, until the entire range has 
rejuvenated. After the vegetative cover has been established, however, the deferred graz- 
ing is alternated or rotated from one portion of the range to another in order to permit 
the formation and distribution of an occasional seed crop by means of which the old plants 
may be replaced. In this way the range is brought back and maintained in its maximum 
state of productivity without the loss of a season's forage crop during the period re- 
quired for revegetation. For full discussion of this subject see : Sampson, Arthur W., 
" Natural Revegetation of Range Lands Based upon Growth Requirements and Life His- 
tory of the Vegetation." Jour. Agri. Research, vol. 3, No. 2, 1914. Sampson, Arthur W., 
" Range Improvement by Deferred and Rotation Grazing." U. S. Dept, of Agr. Bui. No. 
34, 1913. 
