PLANT SUCCESSION AND EANGE MANAGEMENT. 23 
of secondary species is relatively sparse. On the other hand, when 
the soil has been more seriously depleted, these two species merely 
occupy the chief place, many other species, especially grasses, being 
associated with them (fig. 9). Much of the acreage which had 
become so badly depleted in 1905 as to support only a scattered stand 
of the most drought-resistant and short-lived vegetation, has now 
been revegetated to the point of supporting a good, and in some 
instances a maximum, cover of porcupine grass and yellow brush, 
with the scattered admixture of other species, especially grasses high 
in the cycle of development. On areas where the vegetation has for 
one reason or another met with reversals from time to time, porcupine 
grass and yellow brush are much less conspicuous, though they con- 
stitute the predominating species. At this stage in the revegetation 
only the grasses that are characteristic of early successions are asso- 
ciated with the porcupine grass and yellow brush. 
In general, the secondary species of the porcupine-grass-yellow- 
brush consociation are numerous and of much importance economi- 
cally. 1 Among the more common grasses may be mentioned Nevada 
blue grass (Poa nevadensis) , Malpais blue grass (P. scabrella), little 
blue grass (P. sandbergii) , spiked fescue (Festuea eonfinis% western 
fescue (F. occidentalis) , mountain June grass (Koeleria cristiata), 
spiked trisetum (Trisetum spicatum), mountain brome grass (Bromus 
marginatus), Porter's brome grass (B. porter!) , and frequently a 
scattered stand of wheat grasses, of which Scrihner's wheat grass 
{Agropyron scribnerl) is somewhat conspicuous. Typical examples 
of the more important grasses are shown in figure 10. Among the 
more common herbs other than grasses (aside from the ever-present 
yellow brush) are yarrow {Achillea lomvZosa) , sweet sage (Artemisia 
discolor), several species of loco, notably Astragalus decitmbens and 
A, tencllus, single-flowered helianthella (Helianthella. uniflora) geum 
(Geum oregonense), wild bean (Lupinm alpestris), and blue fox- 
glove (Pentstemon procerus). Upon closer view one normally finds 
a very scattered stand of James' chickweed (Alsine jamesiana) , 
scarlet gilia (Gilla pulcheUa), gymnolomia (Gymnolomia muiti- 
fi-ora) : pingue or rubberweed (Hymenoxys floribunda), and others. 
In addition there are a number of inconspicuous annuals. 
These numerous secondary species (fig. 9) vary widely as to 
the distribution of their chief feeding roots. All the more important 
grasses, with the exception of the brome grasses, obtain their moisture 
supply from practically the same soil stratum as does porcupine 
grass. The brome grasses, the locos, and wild bean, on the other 
hand, extend their roots to approximately the same depth as yellow 
brush. Accordingly, single-flowered helianthella, geum gymnolomia, 
1 See also Pound, Roscoe, and Clements, Frederic F., The Phytography of Nebraska, 
381-383, 1900. 
