Page 33 - Soil Degradation, Conservation and Remediation

18 1 Soil Resources and Soil Degradation

1.6.7 Inceptisols

Inceptisols are soils that exhibit only the beginning of soil profi le development.
They are weakly developed soils in that they have minimal horizon differentiation.
They are more developed than Entisols and lack many characteristics of mature
soils. Inceptisols may have many kinds of diagnostic horizons except argillic, natric,
kandic, spodic, and oxic horizons. The most common horizon sequence is an ochric
epipedon over a cambic horizon, with or without an underlying fragipan. Inceptisols
typically have a cambic horizon, but one is not required if the soil has a mollic,
umbric, histic, or plaggen epipedon or if there is a fragipan or duripan or any placic,
calcic, petrocalcic, gypsic, petrogypsic, salic, or sulfuric horizon. Inceptisols are
soils of humid and subhumid regions. Inceptisols are widely distributed and occur
under a wide range of environmental settings. They are often found on fairly steep
slopes, young geomorphic surfaces, wet sites, and on resistant parent materials.
Inceptisols occupy 9.9 % of the global ice-free land surface. (The WRB equivalents
of Inceptisols are Cambisols, Gleysols, and Umbrisols.) Inceptisols have six subor-
ders. They are:

Anthrepts: Anthrepts are more or less freely drained Inceptisols that have either an

anthropic or plaggen epipedon. Most have a cambric horizon. Anthrepts can have
almost any temperature regime and almost any vegetation. Anthrepts are usually
cultivated soils, but some Anthrepts have been diverted to other land uses.

Aquepts: Aquepts are the wet Inceptisols. The water table remains at or near the
surface for much of the year. Most Aquepts have formed in depressions, on

nearly level plains, or on floodplains. Aquepts may have almost any particle-size
class except fragmental. Many Aquepts in floodplains are used for cultivation of

rice.

Cryepts: Cryepts are Inceptisols of the cold regions such as high mountains or high
latitudes. They do not have permafrost within 100 cm of the soil surface. They
may be formed in loess, drift or alluvium (Chap. 3 ), or in solifluction (mass wast-

ing of water saturated soil material down the slope, over impermeable surface)
deposits. Cryepts occur in the USA in the high mountains of the West, southern
Alaska, as well as in other mountainous areas of the world. Vegetation is mostly
conifers or mixed conifers and hardwood forests. Few soils are cultivated.

Udepts: Udepts are mainly the more or less freely drained Inceptisols that have a

udic or perudic soil moisture regime. They are Inceptisols of humid climates.
They are found on nearly level to steeply sloping surfaces. Most of the soils were
originally covered with forest vegetation, with some shrubs or grasses. The
Udepts of the USA are most extensive in the Appalachian Mountains, on the
Allegheny Plateau, and on the west coast. Many Udepts are now under
cropping.
Ustepts: Ustepts are mainly the more or less freely drained Inceptisols that have an

ustic soil moisture regime. Rainfall occurs mainly during the summer. Some
Ustepts are found in older deposits on steep slopes. Native vegetation is com-
monly grass but some supported trees. Most are used as cropland or pasture.