Geoscience Reference
In-Depth Information
Figure 5-7.
Overview of the Bight of Bangkok, Thailand showing extensive rice agriculture in the low-lying coastal
plain and suspended sediment in the bight. International space station, photo ID: ISS023-E-32634. View toward
west, 5 May 2010. Adapted from NASA Gateway to astronaut photography of Earth
<
http://earth.jsc.nasa.gov/
>
.
As soil science matured, the need for a sys-
tematic soil classii cation system grew as well.
During the mid-twentieth century a series of soil
classii cations was developed, which culminated
in the work
Soil Taxonomy
(Soil Survey Staff
1975). The nomenclature was derived mostly
from Greek and Latin words or parts of words
that are added entirely or in part as formative
elements at each successive classii cation level
(Buol et al. 1997). Of the ten original soil orders,
the only one that is clearly associated with wet
soils is the Histosols (Table 5-1). The root
element “histos” was used to indicate that these
soils are composed largely of plant tissue (at
least 20-30% in upper parts). They are essen-
tially the peat, bog, half bog, and muck soils of
earlier classii cations.
Hydric soils are more common in the next
level of classii cation, the suborder. The forma-
tive element “Aqu,” from the Latin
aqua
meaning
water, is added to soils that have aquic moisture
regimes. This implies reducing conditions that
are virtually free of dissolved oxygen, because
the soil is saturated by ground water or by water
of the capillary fringe (Fig. 5-8). These soils are
generally identii ed in the i eld as soils whose
dominant Munsell colors have chromas of 2 or
less and also have brighter colored mottles (Soil
Survey Staff 1975, p. 109). In terms of taxonomic
nomenclature, then, a wet (aquic moisture
regime) Ali sol would belong to the suborder
Aqualf (Aqu for wet and alf for Ali sol). The
same procedure is used for the other orders as
appropriate forming six wet-aquic suborders:
Aqualfs (wet Ali sols), Aquents (wet Entisols),
Aquepts (wet Inceptisols), Aquolls (wet Mol-
lisols), Aquox (wet Oxisols), Aquods (wet Spo-
dosols), and Aquults (wet Ultisols).
The U.S. Fish and Wildlife Service requested
help in the 1970s to develop a practical and
useful classii cation of wet soils for the National
Wetlands Inventory (Mausbach 1994). The intent
