DESERT CLIMAXES. 



229 



"(5) Grazing after seed maturity in no way interferes with flower-stalk 

 production. i& much fertile seed is produced as where the vegetation is 

 protected from grazing during the whole of the year. 



" (6) Germination of the seed and establishment of seedlings depend largely 

 upon the thoroughness with which the seed is planted. In the case of practi- 

 cally all perennial forage species the soil must be stirred after the seed is 

 dropped if there is to be permanent repioduction. 



"(7) Even after a fertile seed crop has been planted there is a relatively 

 heavy loss of seedlings as a result of soil heaving. After the first season, 

 however, the loss due to climatic conditions is negligible. 



" (8) When 3 years old, perennial plants usually produce flower stalks and 

 mature fertile seed. 



" (9) Under the practice of yearlong or season-long grazing both the growth 

 of the plants and seed production are seriously interfered with. A range so 

 used, when stocked to its full capacity, finally becomes denuded. 



" (10) Yearlong protection of the range favors plant growth and seed pro- 

 duction, but does not insure the planting of the seed. Moreover, it is imprac- 

 ticable, because of the entire loss of the forage crop and the fire danger resulting 

 from the accumulation of inflammable material. 



"(11) Deferred grazing insures the planting of the seed crop and the 

 permanent establishment of seedling plants without sacrificing the season's 

 forage or establishing a fire hazard. 



"(12) Deferred grazing can be appHed wherever the vegetation remains 

 palatable after seed maturity and produces a seed crop, provided ample water 

 faculties for stock exist or may be developed. 



" (13) The proportion of the range winch should be set aside for deferred 

 grazii^ is determined by the time of year the seed matures. In the Wallowa 

 Mountains one-fifth of the summer grazing season remains after the seed has 

 ripened, and hence one-fifth of each range allotment may be grazed after 

 that date. 



" (14) The distribution of water and the extent of overgrazing will chiefly 

 determine the area upon which grazing should be first deferred. 



" (15) After the first area selected has been revegetated it may be grazed 

 at the usual time and another area set aside for deferred grazing. This plan 

 of rotation from one area to another should be continued, even after the entire 

 range has been revegetated, in order to maintain the vigor of the forage plants 

 and to allow the production of an occasional seed crop." 



DESERT CLIMAXES. 



MacDaugal (1904) has described the general development of vegetation on 

 the delta of the Colorado River: 



The portion of the delta next the river is an alluvial plain flooded in May, 

 Jime, and July. Nearly pure communities of Salix and Pojndus mexicana 

 coyer many square kilometers, while large areas are occupied by Pluchea 

 sericea, Prosopis velutina, and P- pubescens. Two or three species of Atriplex 

 are also to be found in places where the action of water prevents the establish- 

 ment of woody perennials of greater size. In the upper part of the delta, 

 Phragmites fringes the channel, and aids in preventing the erosion of the banks. 

 It is replaced by Typha angiistifolia in the lower part of the delta affected by 

 spring tides. The forests of willow and poplar thin out at 50 to 60 km. from 

 the Gulf of California, the poplar disappearing first. Beyond occur the mud 

 plains, covered thickly with Distichlis and Cressa truxillensis, where not sub- 



