238 THE FUTURE OF ARID LANDS 
former grassland sites are responsible for lowering grazing capacity, 
especially where grazing pressure has been heavy. Forage produc- 
tion can be increased by removing these shrubs. For example, in 
southern Arizona removal of mesquite (Prosopis juliflora var. 
velutina (Woot.) Sarg.) on grassland sites when accompanied by 
conservative grazing has increased perennial grass forage produc- 
tion fourfold. There are other important benefits from mesquite 
control. Erosion ordinarily active under mesquite is reduced by 
the reestablishment of grasses. Cattle are also more easily worked 
and losses from screwworm are reduced (10). 
Considerable research is being done to find control methods for 
many other undesirable plants. Much progress has been made. It 
must always be kept in mind, however, that there is no perma- 
nent advantage in the mere killing of low-value plants unless 
their elimination is followed. by grazing practices which permit 
increases in desirable forage species. 
Reseeding of Adaptable Grasses 
Heavy grazing, drought, the spread of noxious plants, and the 
combination of these factors have depleted the grasses and other 
forage plants on large areas. Restoration of much of this land 
within a reasonable length of time depends on the development 
of practical economic methods for range reseeding. To date, suc- 
cessful methods have been worked out for reseeding many arid 
sites. However, much remains to be done, and an expanded re- 
search program is justified. 
Most success with range reseeding on arid sites has been with 
the use of introduced grasses. Several species of lovegrasses 
(Eragrostis spp.) introduced from South Africa have been used 
successfully in Arizona and New Mexico. Mild winters, hot sum- 
mers, and annual precipitation of at least 11 inches, mostly 
received in the growing season, characterize these areas (1, 13). 
Grasses from Asia and the Middle East such as crested (/gro- 
pyron desertorum (Fisch.) Schult.) and intermediate (4. inter- 
medium (Host.) Beauv.) wheatgrasses and Russian wildrye 
(Elymus junceus Fisch.) have proved well adapted to areas where 
winter temperatures are lower and more of the precipitation occurs 
