PLANT SUCCESSION AND RANGE MANAGEMENT. 53 



though with less relish than sheep. Several of the more conspicuous 

 plants, like tarweed, gilia, etc., are practically disregarded by stock. 



FORAGE PRODUCTION. 



The amount of forage produced on lands in the first or early weed 

 stage is far less than that on lands supporting any of the higher stages 

 of plant growth. Like the second or late weed cover, the ruderal-weed 

 cover is best suited for the grazing of sheep, but the carrying capacity 

 is exceedingly low and the forage distinctly inferior. Aside from 

 the fact that little of the herbage produced is grazed after about the 

 first week in August, anything approaching complete utilization of 

 the forage crop is apt to stimulate erosion of a most destructive char- 

 acter. Hence range lands in the ruderal-weed stage must be man- 

 aged in the most expert way ; anything approaching maximum utili- 

 zation is hardly to be considered if the more permanent and desirable 

 cover is ultimately to gain dominion over the soil. 



SUMMARY OF THE RUDERAL-EARLY-WEED CONSOCIATION. 



On lands where the soil has been so seriously impaired as no longer 

 to afford a congenial habitat for the growth of perennial species, the 

 cover consists essentially of annual plants. This first or early weed 

 stage of which goosefoot or lamb's-quarters, slender-leaved coUomia 

 tarweed, Tolmie's orthocarpus, Douglas knotweed, and tansj^^ mus- 

 tard are typical examples, completes its gi'owth in about 6 weeks 

 after the sprouting of the seed. As the plants are entirely dependent 

 upon seed for their perpetuation, their seed habits are exceptionally 

 strong, the viability of the seed from j^ear to year averaging con- 

 siderably higher than that of the perennial plants. In spite of 

 strong seed habits, however, there is a wider variation from year to 

 year in the density of the stand of the early-weed stage than in any 

 other tjpe. This is chiefly due- to the fact that there is not always 

 ample moisture for plant life in the superficial soil layer in which the 

 feeding roots of this consociation are located. While often variable 

 in density, the ruderal-weed type nevertheless persists until enough 

 organic matter has been accumulated in the soil to favor the estab- 

 lishment of plants of the second-weed stage. 



Little forage is produced by the first-weed type. A'S'Tiile a consid- 

 erable number of species are grazed by sheep (few are eaten by cattle 

 and practically none by horses), only a small amount of dry matter 

 is produced. Douglas knotweed, the most abundant species, is 

 cropped with moderate relish both by sheep and cattle and probably 

 furnishes as much feed as all the other annuals combined. However, 

 the ruderal-weed cover is grazed only when the herbage is succulent 

 and tender. In view of the early maturity of the vegetation and the 

 fact that the first-weed-stage cover affords poor protection of the 



