320 GRAZING INDICATORS. 



one used by cattle or horses. Under climax conditions, the grasses are able 

 to maintain their dominance in competition with the herbs, but in the case of 

 overgrazing or other disturbance, the latter gradually get the upper hand. 

 When the area is protected or the grazing reduced, the advantages of the grass 

 life-form again come into play in the competition, and the herbs disappear or 

 become subdominant. As a consequence, the best method of eradicating 

 weeds is by protection or regulated grazing. Complete protection is more 

 rapid in its effects, but it is usually out of the question. Regulated grazing 

 is the most practicable method as a general rule, but it is sometimes too slow 

 in operation, or the area is too thoroughly dominated by weeds to permit it. 

 This is particularly the case with areas densely covered with prostrate species 

 of prickly pears, such as Opuntia mesacantha and 0. polyacantha, or with 

 half-shrubs, such as Gutierrezia. 



When it is desired to get rid of annual weeds more rapidly than by means of 

 regulated grazing, they may be grazed off by sheep, especially where mixed 

 grazing is practiced. They may be greatly reduced by burning at the time 

 when their seeds are ripening, and they may even be mowed where the area 

 permits. During favorable seasons, their disappearance may be hastened by 

 overplanting with more vigorous species, especially perennials, which increase 

 the natural rate of succession. Perennial weeds are more difficult to get rid of, 

 since they are less affected by burning or mowing, and it is too expensive to 

 grub them out on the range as a rule. Fortunately, the most serious pests 

 are cacti and half-shrubs, which lend themselves to various methods of clear- 

 ing. Since cacti furnish succulent forage when more or less spineless, the 

 most satisfactory method of eradication is by burning, when the tract con- 

 tains enough grass to permit this, or by singeing with a torch when the area 

 is almost pure. Once the spines are removed from the prickly pears, they 

 will be grazed down to the ground by cattle, and in a few years will practically 

 disappear from the range if overgrazing is prevented. Halfshrubs, Uke other 

 weeds, can best be eUminated by protecting the areas or grazing them lightly, 

 but many ranges are so densely covered with Gutierrezia or Isocoma, for ex- 

 ample, that other methods must be employed. Since these rarely root- 

 sprout, burning is the quickest and most economical method, though in small 

 areas they may be cut out with profit. 



Eradication of brush. ^The range value of brush is determined primarily 

 by its palatabiMty, but it depends in a large measure also upon whether it is 

 pure or mixed with grass. As has already been emphasized, a range made up 

 of grass and browse in more or less equal degree permits mixed grazing and 

 furnishes the best insurance against drought and other disasters. The 

 burning of unpalatable brush to clear the ground for herbaceous growth seems 

 to have been long practiced in California, and it has also been employed to 

 maintain the stand of grass against the encroachments of shrubs in mixed 

 types. In the case of the Coastal chaparral, the dominants form root-sprouts 

 in great abundance and repeated burning is necessary to maintain the herb 

 cover. This is less true as a rule in the Petran type, where burning is chiefly 

 important in enlarging the grass areas, as is the case Hkewise in the subclimax 

 chaparral of Texas. In the typical savannah of the Southwest, the mesquite 

 and its associates are kept down by burning and the grassland chmax favored. 

 In the case of sagebrush, grazing by cattle favors the shrubs at the expense of 



