RANGE PRESERVATION AND EROSION CONTROL. 23 
owing to the low moisture content due to exposure and lowered 
water-holding power, seed germinate poorly. Moreover, about nine- 
tenths of the plants which do come up die early in the- spring while 
still in the seedling stage. The remainder usually dry up before the 
end of the season. 
Interesting contrasts have been recorded on the mountain ranges 
of the Manti National Forest as to the rate of revegetation and the 
character of species being established on overgrazed and subsequently 
eroded lands as compared with lands which have not been seriously 
overgrazed, and where the soil, therefore, is relatively productive. 
During observations extending over four years (1913-191G) it was 
most exceptional to find on the more seriously eroded soils an increase 
in the number or appearance of new deep-rooted perennial species of 
any kind. On the less seriously eroded soils, on the other hand, 
shallow-rooted perennial species, both seedlings and matured speci- 
mens have gradually increased in number each season ; and on some- 
what overgrazed, but not eroded lands, deep-rooted perennials have 
increased relatively rapidly and steadily. 
On analyzing the data recorded as to the rate and character of 
the revegetation it was found that by noting the seriousness to which 
the soil has been eroded, and hence its physical condition, including 
the relative amount of organic matter contained in it, it is possible 
to predict with much precision not only the rate at which the ground 
cover may be restored but the- particular kind of plants that will 
occupy the soil for a temporary period prior to establishment of a 
permanent vegetation. As a general thing, many years must lapse 
before the more desirable forage species can reoccupy the site upon 
which the3 T formerly predominated. The reestablishment of the 
deeper-rooted perennial species, if this type of vegetation is desired, 
and it usually is, can be accomplished on these eroded soils under 
range conditions only by certain rather inconspicuous plants first 
gaining a foothold on the land and gradually reinstating the vege- 
table matter and plant foods which are invariably lacking. 
The- replacement of one set of plants by another through a series 
of successive invasions is known as plant succession. Where the fer- 
tility of the soil has been seriously impaired only rapidly growing 
and early maturing annual species first occupy the soil. Several 
species of this type of vegetation begin germination and growth 
promptly in the spring, and before the soil has dried out to a point 
where the vegetation wilts beyond recovery and further growth, the 
plants have developed fully and ripened an abundant seed crop of 
good germination strength. The ramifications of the roots of these 
inferior plants through the soil season after season, the aeration 
of the upper soil layer as a result of the innumerable penetrations 
