Environmental Engineering Reference
In-Depth Information
forests are cleared. Figure 3-22 profiles five important
soil types.
Soils vary in their content of clay (very fine parti-
cles), silt (fine particles), sand (medium-size particles),
and gravel (coarse to very
coarse particles). Take a
small amount of top-
soil, moisten it, and
rubitbetween your fingers and thumb. A gritty feel
means it contains a lot of sand. A sticky feel means a
high clay content, and you should be able to roll the
soil into a clump. Silt-laden soil feels smooth, like
flour. A loam topsoil, which is best suited to plant
growth, has a texture between these extremes—a
crumbly, spongy feeling—with many of its particles
clumping loosely together.
Mosaic
of closely
packed
pebbles,
boulders
Weak humus-
mineral mixture
Alkaline,
dark,
and rich
in humus
Dry, brown to
reddish-brown
with variable
accumulations
of clay, calcium
carbonate, and
soluble salts
Clay,
calcium
compounds
Desert Soil
(hot, dry climate)
Grassland Soil
(semiarid climate)
Forest litter
leaf mold
Humus-mineral
mixture
Light, grayish-
brown, silt loam
Dark brown
firm clay
Acid litter
and humus
Acidic
light-
colored
humus
Light-colored
and acidic
Iron and
aluminum
compounds
mixed with
clay
Humus and
iron and
aluminum
compounds
Tropical Rain Forest Soil
(humid, tropical climate)
Deciduous Forest Soil
(humid, mild climate)
Coniferous Forest Soil
(humid, cold climate)
Active Figure 3-22 Natural capital: soil profiles of the principal soil types typically found in five types of ter-
restrial ecosystems. See an animation based on this figure and take a short quiz on the concept.
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