PLA^STT STJCCESSIOlSr A^TD RAI^TGE MAITAGEMENT. 73 



are highly palatable to sheep but which may be grazed little or not 

 at all by cattle and horses. Likewise a weed cover grazed exclusively 

 by sheep will sooner or later change to the grass stage. 



INDICATORS AND THEIR USE. 



The data in this bulletin jvistify the conclusion that the character 

 of the native vegetation can be used as a reliable indicator of the 

 condition of the range and of the effect of a given method of grazing 

 on the plant cover. 



The plant indicators signifying the waning of the wheat-grass 

 cover are essentially porcupine grass and yellow brush; the retro- 

 gression of the porcupine-grass-yellow -brush cover is indicated by 

 species of the second-weed stage of which blue foxglove, sweet sage, 

 and yarrow are the most characteristic ; the giving way of the second- 

 weed-stage cover, here recognized by blue foxglove, sweet sage, and 

 yarrow, is indicated by the appearance of low pea vine, evening prim- 

 rose, false cymopterus, Mexican dock, and tongue-leaved violet, in 

 addition to several species of first-weed-stage plants of which goose- 

 foot, slender-leaved collomia, tarweed, Tolmie's orthocarpus, and 

 Douglas knotweed are typical; and the recession or destruction of 

 the first or early weed stage is marked, first, by the thinning out and 

 decrease in the luxuriance of growth of the annual species, and, 

 ultimately, by the erosion of the soil to the extent of exposing the 

 underlying rock and destroying the holdfast for herbaceous vege- 

 tation, thus favoring the reappearance of lichens and algae of the 

 initial or pioneer stage. 



APPLICATION OF PLANT SUCCESSION TO RANGE MANAGEMENT. 



The species that are increasing appreciably on the range invariably 

 reveal one of two stories. If the invading plants are lower in the 

 succession than the predominating vegetation, the range is being 

 utilized unwisely in one or more respects. If the incoming vegetation 

 is somewhat higher successionally than the type as a whole, improve- 

 ment under the management in vogue is sure to follow. Where the 

 negative indicators are crowding out the more permanent and de- 

 sirable species, remedial measures should be adopted with a mini- 

 mum loss of time. 



Since, as pointed out, range depletion is due chiefly to too early 

 cropping or to overgrazing, the application of the deferred-and-rota- 

 tion grazing system, coupled with a correct estimate of the carrying 

 capacity of the range, may be relied upon fully to revegetate the 

 lands where enough plants of desirable species are found for seed 

 production. Areas in the first-weed stage, in the absence of desirable 

 forage plants, should not be included in the general j)lan of deferred 



