Fig. 9. Perhaps the most significant land-use change in the Cen- 
tral Management Unit was the breaking of the prairies for small 
grain production. Sorghum is the major grain produced in the 
southern part of the unit. Crosby County, Texas. (Photo by 
R. M. Kral, USDA-SCS). 
amount of “edge.” In the drier western portions of the 
CMU, precipitation is normally too unreliable for sustained 
dry-land crop production. Development of irrigation sys- 
tems, either as gravity flow from impounded reservoirs or 
pumped from aquifers, has permitted productive farming 
of lands otherwise unsuited for intensive agriculture. 
Conversely, removal of shrubs and trees throughout the 
CMU has resulted in loss of important nesting sites for 
mourning doves, In southwestern areas, extensive programs 
of brush control and phreatophyte removal have been 
implemented during the past 20 years to improve pastures 
and conserve water (Fig. 12). 
Of particular concern is the relatively recent practice of 
eliminating shelterbelts in the Great Plains of the CMU. 
These windbreaks were originally planted to reduce wind 
erosion of prairie soils and to protect buildings and live- 
stock. Many of the shelterbelts date back to the mid-1930's 
when more than 200 million seedling trees were planted 
on 30,000 farms in six Great Plains States (Comptroller 
General of the U.S, 1975). These and later plantings have 
provided badly needed protection from winds during 
droughts. Removal of the shelterbelts in recent years has 
been precipitated by overmaturity and death of some of 
the trees, and by a desire of farmers to put more of their 
land into direct production of crops. Although farmers 
recognize the wind-reduction and increased-humidity bene- 
fits of windbreaks, continued retention in many situations 
is not compatible with modern agricultural practices such 
as mechanized harvesting and center pivot irrigation sys- 
tems. Soil Conservation Service officials fear that the con- 
tinued removal of windbreaks in the Great Plains could 
have an adverse effect in future years on soil conservation, 

- . a _ _ 
ee ee 
Og tee A ee 

Fig. 10. In many sections of the middle and northern Central 
Management Unit, the original grasslands have been replaced 
by corn and small grain. Farmstead and field shelterbelts pro- 
vide important nesting sites, whereas waste grain furnishes food. 
Brown County, South Dakota. (Photo by R. B. Branstead, 
USDA-SCS). 

Fig. 11. Water provided by a stockpond and suitable nesting cover 
afforded by trees and brush contribute to this good mourning 
dove nesting habitat. Western North Dakota. (Photo by D. R. 
Warren, USDA-SCS). 
wildlife, and the general environment (Comptroller Gen- 
eral of the U.S. 1975), 
Whereas the presence of trees and brush in grassland 
areas may not always constitute a critical need of doves (as 
doves also nest on the ground), existing evidence strongly 
suggests that doves prefer tree nesting sites over ground sites 
in the Great Plains (Downing 1959; Stewart 1975; Olson 
1980). 
