II. DESERT SOILS
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has very little soil. Most of the surfaces are barren, rough land of rocks
and stony colluvial debris and outwash gravels. Even the more level terrain
of the Meseta Central (20°-25°S latitude) is coarse material of geological
erosion from the Andes. Agriculture is confined to the narrow river terraces and somewhat wider flood plains in the bottom of deep canyons and
scattered oases. The rich nitrate beds west of Meseta Central are located
on smooth, gently undulating slopes completely free of soil. Borax "lakes"
and saline "dry lakes" also are common to the Atacama-Loma Desert region (Cameron et al., 1965). Soils of this desert are limited to a few
scattered Entisols or Aridisols.
North of Meseta Central the soils are salty and alkaline. South of this,
however, they are less salty and appear as fine-textured marine terraces
with some profile development. Scattered desert shrubs dot these terraces.
In general, dunes so prevalent in the Peruvian Desert are not conspicuous
in the Atacama Desert of Chile.
Vegetation in the Atacama Desert is confined to a few shrubs along
the coast and rock lichens. The Peruvian Desert is a continuation of the
coastal desert of Chile where it is somewhat broader (Meigs, 1953) in
Peru. Only the soils of the northern part of the coastal plain are appreciably developed. As reported in the soils inventory by Dregne (1967),
about 5% of the arid coastal region is alluvial soil, 65% are Lithosols,
25% are Regosols, and 5% are red desert and black clays. Agriculture
is located on the alluvial soils of the transverse valleys along the coastal
plains bordering the numerous rivers that flow into the Pacific. The red
desert soils occur in the Northern Peruvial Desert where rainfall is slightly
higher 2-25 cm/year. These are fine-textured, deep soils having lime concretions and lime horizons. Gray Desert soils of clay texture also are found
here although they are deep, they are quite impermeable and alkaline.
Vegetation in the Atacama-Peruvian Desert is very scarce (McGinnies,
1967) except along streams and rivers. Sparse stands of Tillandsia may
appear during the more moist winter months. Lichens occur on rocks
(Cameron et al., 1965). Some ephemeral vegetation is found on mistcovered (150-1500 meter) elevations. Vegetation is primitive and microbial populations favor the autotrophic rather than heterotrophic organisms
such as the lichen and algae. Compared with other deserts of North and
South America, Cameron et al. (1965) claim the soils contain a very low
abundance of common groups of microorganisms.
M. NORTH AMERICAN
North American Desert soils are bordered by the Chihuahuan and
Sonoran Deserts in Mexico on the south, and the Columbia Basin and
89
has very little soil. Most of the surfaces are barren, rough land of rocks
and stony colluvial debris and outwash gravels. Even the more level terrain
of the Meseta Central (20°-25°S latitude) is coarse material of geological
erosion from the Andes. Agriculture is confined to the narrow river terraces and somewhat wider flood plains in the bottom of deep canyons and
scattered oases. The rich nitrate beds west of Meseta Central are located
on smooth, gently undulating slopes completely free of soil. Borax "lakes"
and saline "dry lakes" also are common to the Atacama-Loma Desert region (Cameron et al., 1965). Soils of this desert are limited to a few
scattered Entisols or Aridisols.
North of Meseta Central the soils are salty and alkaline. South of this,
however, they are less salty and appear as fine-textured marine terraces
with some profile development. Scattered desert shrubs dot these terraces.
In general, dunes so prevalent in the Peruvian Desert are not conspicuous
in the Atacama Desert of Chile.
Vegetation in the Atacama Desert is confined to a few shrubs along
the coast and rock lichens. The Peruvian Desert is a continuation of the
coastal desert of Chile where it is somewhat broader (Meigs, 1953) in
Peru. Only the soils of the northern part of the coastal plain are appreciably developed. As reported in the soils inventory by Dregne (1967),
about 5% of the arid coastal region is alluvial soil, 65% are Lithosols,
25% are Regosols, and 5% are red desert and black clays. Agriculture
is located on the alluvial soils of the transverse valleys along the coastal
plains bordering the numerous rivers that flow into the Pacific. The red
desert soils occur in the Northern Peruvial Desert where rainfall is slightly
higher 2-25 cm/year. These are fine-textured, deep soils having lime concretions and lime horizons. Gray Desert soils of clay texture also are found
here although they are deep, they are quite impermeable and alkaline.
Vegetation in the Atacama-Peruvian Desert is very scarce (McGinnies,
1967) except along streams and rivers. Sparse stands of Tillandsia may
appear during the more moist winter months. Lichens occur on rocks
(Cameron et al., 1965). Some ephemeral vegetation is found on mistcovered (150-1500 meter) elevations. Vegetation is primitive and microbial populations favor the autotrophic rather than heterotrophic organisms
such as the lichen and algae. Compared with other deserts of North and
South America, Cameron et al. (1965) claim the soils contain a very low
abundance of common groups of microorganisms.
M. NORTH AMERICAN
North American Desert soils are bordered by the Chihuahuan and
Sonoran Deserts in Mexico on the south, and the Columbia Basin and