PLAXT SUCCESSIOK' AISTD KAISTGE 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 stag'e 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.^ Among the more common grasses may be mentioned Nevada 

 blue grass {Poa nevadensis) , Malj)ais blue grass {P. scdbreUa)^ little 

 blue grass {P. sandhergii) , spiked fescue {Festuca con-finis), western 

 "fescue {F. accidentalis) , mountain June grass {Koeleria cHstata), 

 spiked trisetum {TrisetuTn sjncatum) , mountain brome grass {Btotyius 

 m/irginatus)y Porter's brome grass {B. forteri), and frequently a 

 scattered stand of wheat grasses, of which Scribner's wheat grass 

 {Agrojyyro^i scrihneri) 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 lanulosa), sweet sage {ArteTnism 

 discolor), several species of loco, notably Astragalus decumhens and 

 A. teneUus, single-flowered helianthella {Helianthella unif^ora) geum 

 {GeuTTi, oregonense), wild bean {Lupinus alpestr^is), and blue fox- 

 glove {Pentstemon procams). Upon closer view one normally finds 

 a very scattered stand of James' chickweed {AIsItis jamesiana), 

 scarlet gilia {Gilia pulcheUa), gymnolomia {Gymnolomia mu\l.ti- 

 -flora), pingue or rubberweed {Hymenoxys fjoribunda) , 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, 



^ See also Pound, Eoscoe, and Clements, Frederic F., The Phytography of Nebraska, 

 381-383, 1900. 



