PLANT SUCCESSION AND RANGE MANAGEMENT. 69 



19. A reliable indication pointing toward the maintenance, or the 

 progressive development of this cover, is an increasing density and 

 luxuriance of growth of certain blue grasses, and in some instances 

 fescues, and a decreasing stand of the brome grasses, and under 

 certain conditions of yellow brush and other deep-rooted species. 



20. With its large variety of palatable grasses and other plants 

 this consociation is probably second to none in forage value, all 

 classes of stock considered. 



21. In general the highest possible development of this consocia- 

 tion affords the most nutritious forage cover, and will probably 

 support more stock than will any other stage of plant development. 

 It is a mixed grass-and-weed type, with the grasses distinctly pre- 

 dominating, and the highest grazing efficiency is obtained through 

 " combination " or " common-use " grazing, that is, the grazing of 

 cattle, sheep, and horses. 



THE rOXGLOVE-SWEET-SAGE-TARROW COXSOCIATION. 



22. Where conditions on the porcupine-grass-yellow-brush cover 

 are such as slightly to decrease the fertilitj^ and water-holding power 

 of the soil, blue foxglove, sweet sage, and yarrow, the most char- 

 acteristic species of the second-weed stage, are among the first plants 

 to establish themselves. Where the fertilit}^ and water absorptive 

 capacity of the soil are seriously impaired, porcupine-grass-yellow- 

 brush cover is succeeded by annual plants characteristic of the early 

 or first weed stage. 



23. Generally the invasional activity of the succeeding late-weed- 

 stage plants is most vigorous shortly after the destruction of the 

 grass-brush cover. 



24. A large number of species, including some grasses, are asso- 

 ciated with blue foxglove, sweet sage, and yarrow, but they seldom, 

 if ever, occur as dominants. Like the dominant plants, the secondary 

 species are moderately deeply rooted, the water supply being drawn 

 very largely from the upper 2 feet of soil. 



25. Blue foxglove, sweet sage, and yarrow reproduce both by seed 

 and by vegetative means, the latter method being so active that the 

 cover characteristically forms a somewhat loose, matlike surface. 

 The seed habits are only moderately strong, yet invasion is fairly 

 active under favorable conditions of germination and growth. 

 Seedling plants as a rule do not produce either fertile seeds, or many 

 shoots from the rootstocks, until the third year of growth. 



26. Low pea vine, evening primrose, false cymopterus, Mexican 

 dock, and tongue-leaved violet are the most reliable indicators of the 

 waning of the more permanent and typical second-weed-stage cover. 

 With the exception of pea vine the regeneration of these" species is 



