Geoscience Reference
In-Depth Information
Chapter 8
Histic and Folistic Epipedons
8.1
Introduction
The histic and folistic epipedons differ from the other six pedons in that they are
comprised dominantly of organic soil materials. In
Soil Taxonomy
, the folistic
epipedon is defined as an organic horizon that is saturated for
30 days per year
<
in normal years and is
20 cm thick, depending on the proportion of
Sphagnum
fibers. In contrast, the histic epipedon is an organic horizon that is
saturated for
15 or
>
>
30 days per year in normal years and is at least 20-40 cm thick.
Both epipedons may be within an Ap horizon, depending on the amount of SOC in
relation to the amount of clay. These horizons are comparable to the histic and folic
horizons in the World Reference Base with the exception that the WRB has a 10-cm
minimum thickness requirement for both horizons.
In the USA folistic epipedons are most common in the mountains of HI, but they
are also present at the higher elevations in the southern and northern Appalachian
Mountains. Folists in Canada were reviewed by Fox and Tarnocai (
2011
). Soils
with a histic epipedon are either organic soils (Histosols) or less commonly hydric
soils, i.e., soils in Histi- great groups of Gelisols and histic subgroups of aqu-
suborders in Alfisols, Andisols, Entisols, Inceptisols, Mollisols, and Spodosols.
Soils with a histic epipedon were studied in detail by Everett (
1983
), Klinger
(
1996
), and D'Amore and Lynn (
2002
) in AK and Richardson et al. (
2009
)in
Florida (FL) and by Gignac and Vitt (
1994
) and Kroetsch et al. (
2011
) in Canada.
>
8.2 Properties of Folistic and Histic Epipedons
Examples of soils with folistic and histic (Sapristel) epipedons are shown in
Figs.
8.1
and
8.2
, respectively. Tables
8.1
and
8.2
give properties of the folistic
and histic epipedons, respectively. The folistic and histic epipedons are depicted in
boldface. The properties of the folistic and histic epipedons are comparable, with
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