RANGE MANAGEMENT IN NEW MEXICO, 7 
region and accepted as the natural order of things; but it is of vastly 
more importance in regions of scanty rainfall. Here any kind of 
management that permits or assists in the waste of water in any 
way tends in the long run to the desiccation of the region. Hence, 
any practice that increases the rapidity or amount of superficial run- 
off or increases the evaporation of water (other than that which passes 
through the bodies of growing plants) makes for the gradual drying 
out and increased sterility of the region. These processes are cumu- 
lative, and regions that are easily habitable under one kind of treat- 
ment may be gradually changed to desert wastes by another pro- 
cedure which, to the careless observer, does not seem materially 
different from the first. 
SOILS. 
Speaking very generally, the soils of most localities in the State 
have been formed almost in situ by the disintegration of the under- 
lying or near-by rocks and necessarily have the chemical composi- 
tion arising from the breaking up of these rocks, mechanical or chem- 
ical, or both. The soils of the river valleys have been transported 
considerable distances and the particles assorted to size by the action 
of the water. They consist mostly of sand or adobe and are uniform 
in character and depth only for very short distances, because of the 
great variations in the volume and velocity of the waters of the 
streams that have deposited them. 
The soils of the larger and higher mountains, wherever they occur, 
are mostly a rather rich loam, due to the nearly complete chemical 
decomposition of the rocks, and contain considerable humus derived | 
from the vegetation of such regions. The foothills of the mountains 
are mostly flanked by talus slopes and outwash plains composed of 
partially disintegrated rock particles of various sizes, forming grav- 
elly ridges and slopes in which proper soil particles constitute only a 
small part of the volume. 
The soils of the plains and bolsons are largely wind-blown sand or 
loess. In the bottoms of the basins such soils are sometimes deep, 
but mostly they form only a thin layer. 
Wherever the water collects, evaporation goes on rapidly, with a 
consequent accumulation of the soluble salts of sodium and calcium 
known as alkali. Alkali often occurs in the river valleys in the soil 
of terraces whose surfaces are but 2 or 3 feet above the water table, 
as a result of the concentration of these salts at the surface by evapo- 
ration. 
The lava-covered areas are in places but bare black rock, with scat- 
tered patches of loess or sand in depressions and behind projecting 
angles. In other places, where the lava is older, the basalt has de- 
composed to a rich reddish loam, a soil that is recognizedly one of 
the best. 
