Geoscience Reference
In-Depth Information
and Umbrisols. An example is the suborder Ustepts, great group Calciustepts, and
subgroup Udic Calciustepts.
Mollisols have the formation element
oll
. The name has its roots in the Latin
mollis
which means soft. They were developed in semiarid to subhumid climate
where grasses dominated. Their profi le does not indicate strong leaching - it could
even be absent. They include the WRB Chernozems. And WRB Gleysols,
Kastanozems, and Phaeozems appear among suborders of our Mollisols (see
Ustolls). An example is the suborder Xerolls, great group Durixerolls, and subgroup
Vertic Durixerolls.
Oxisols have the formation element
oxi
. The name is related to the term oxide.
Very old soils belonging to this group were strong weathered in humid tropical cli-
mate with intensive leaching of Fe and Al oxides recognized by red color, especially
in the illuvial horizon. They were earlier recognized as Latosols or Lateritic soils.
WRB classifi cation identifi es them as Plinthosols and Ferralsols. An example is the
suborder Ustox, great group Haplustox, and subgroup Plinthic Haplustox.
Spodosols have the formation element
od
. Their name was derived from the
Greek
spodos
meaning ash. They are frequent in cold, moist climate with precipita-
tions much higher than evaporation where the soil water fl ux is directed downward.
Fe and Al oxides released from an acidic horizon are transported down to less acid
horizon where they are accumulated. The leached eluviated horizon below the thin
top horizon has a light gray to whitish color resembling the color of ash. The illuvi-
ated horizon has typical colors of rusty brown hues or dark brown. The original
plants were coniferous trees and their needles contributed to the soil acidity. WRB
classifi es these soils as Podzols. An example is the suborder Orthods, great group
Alorthods, and subgroup Arenic Ultic Alorthods.
Ultisols have the formation element
ult
. The name was derived from the Latin
ultimus
which means last. Evolving in humid tropical and subtropical climates that
cause soil water saturation for portions of each year, their profi les contain mottled
horizons and display other signs of waterlogging. They are identical with WRB
Alisols, some Nitisols, while Ultisols' suborder Udults have all signs of WRB
Acrisols. An example is the suborder Udults, great group Plinthudults, and sub-
group Typic Plinthudults.
Vertisols have the formation element
ert
. The name has roots in the Latin
vertere
which means to turn. They are texturally heavy soils changing their volume with
changes of water content. They are swelling when they are becoming water satu-
rated, and they are consistently cracking each year during dry seasons. They have all
the characteristic properties described in WRB Vertisols. An example is the subor-
der Xererts, great group Durixererts, and subgroup Halic Durixererts.
Soil faces differ from one location to another and are not uniform. We illustrate
some of their unique, identifying features in the next dozen fi gures (Figs.
13.1
,
13.2
,
13.3
,
13.4
,
13.5
,
13.6
,
13.7
,
13.8
,
13.9
,
13.10
,
13.11
,
13.12
, and
13.13
). The soil
profi les demonstrated here reach roughly to a depth 1 m below the surface. The type
of each soil is in the US classifi cation at the level of order and suborder. In the World
Reference Base (WRB), the Reference Soil Group (RSG) is indicated. If not
indicated otherwise, the fi gures stem from the collections of Jan Nemecek, the
Czech top pedologist. We are much obliged to him for his kindness.
