rainfall. The area, geologically, is known as the Modoc Plateau, a highland 
region with surface deposits of recent basalt plains and several volcanic 
shield cones. These structures, for the most part, overlap older Basin-Range 
structures. Many basins include sedimentary rocks from material deposited in 
Quaternary lakes resulting from interruption of the drainage networks by 
faulting or volcanism. The lake sediments are tuffaceous siltstones with some 
ashy sandstones; the volcanic rocks include basalt and andesite lava, and 
mudflows. Many of the shield volcanoes are composed of basalts, but some 
andesite is present; some lava flows in this region are less than 2000 years 
old and highly fractured resulting in rapid subsurface drainage with numerous 
springs evident on the side slopes. The vegetation community is dominated by 
Western juniper ( Juniperous occidentalis ), Big sagebrush ( Artemisia tridentata ), 
Low sagebrush ( A. arbuscula ), Antelope bitterbrush ( Purshia tridentata) , 
Rubber rabbitbrush ( Chrysothanmus nauseosus) , Douglas (or Lanceleaf) rabbitbrush 
(C.vicidiflorus); herbaceous vegetation is dominated by Cheatgrass ( Bromus 
tectorum ), Sanburg’s bluegrass ( Poa secunda ), Bearded bluebunch wheatgrass 
(Agropyron spicatum ), Idahoe fescue ( Festuca idahoensis ); and Needlegrass 
(Stipa spp .); the remaining vegetation includes annual and perennial forbs 
with some moist areas having Quaking aspen ( Populus tremuloides ) and Willow 
( Salix spp ) stands. 
METHODS 
The major responsibilities of BLM resource specialists and land managers, 
in addition to conducting daily management programs, inalude making grazing 
allotment plans; developing wildlife habitat plans; determining flood hazards; 
monitoring and preventing soil erosion; determining forest harvesting practices; 
developing recreation plans; establishing fire protection plans; identifying 
and monitoring sensitive ecological areas; developing fisheries habitat plans; 
devising hazard reduction programs; and coordinating programs with local 
governments and other federal and state agencies. Basic inventory data relative 
to livestock forage; wildlife habitat; watersheds; minerals, timber production; 
recreation; the protection of lands, roads, and trails, and the preservation, 
of other public values are compiled in map overlay, tabular and/or narrative 
form. These resource data allow the resource manager to evaluate the comple 
mentary and competing uses of resources and to rationally consider possible 
management alternatives. It was determined that basic vegetative, soil, and water 
inventory information would be not only the most feasible remote sensing data 
products to inventory, but also the most useful information for a majority of the 
resource managers utilizing the data products. The vegetation mapping for this 
project was confined within the administrative boundaries of two resource planning 
units while soil resource evaluation and mapping was confined to four ecologically 
distinct areas within parts of two planning units. 
Data Acquisition and Use 
Three types of data were acquired and subsequently analyzed for this 
project. These include: space imagery from the ERTS-1 vehicle; aerial photography