Ortstein and Placic Horizons - Soil Geography of the USA: A Diagnostic-Horizon Approach - page 193

Table 18.3 (continued)

No. of soil series
Full ortstein Suborder/great group Subgroup Some ortstein No ortstein

Lithic 0 0 1

Cryods, subtotal 4 0 7

Humods
Haplohumods Typic 0 0 2

Durihumods Andic 1 0 0

Humods, subtotal 1 0 2

Spodosols, total 47 42 59

Placic
Aquepts
Epiaquepts

Humic 1

Petraquepts Placic 2

Histic Placic 1

Aquods
Cryaquods Placic 1

Orthods
Placorthods

Typic 1

Udands
Placudands

Typic 1

Total 7

18.4 Distribution of Soils with Ortstein and Placic Horizons

A total of 47 soil series with 50 % ortstein in the spodic horizon are contained in the

USDA NRCS database. These soils comprise 257,000 ha in the USA and occur
primarily in MI (134,000 ha) and FL (74,000 ha) (Table 18.4 ). However, there are
an additional 42 soil series that contain spodic materials that are

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50 % cemented but
were identified in official soil descriptions as ortstein. These soils occur primarily in
MI (863,000 ha combined), FL (761,000 ha), andWI (135,000 ha). These data suggest
that there are at least 2.2 million ha of soils with some form of ortstein, 87 % of which
occur in MI and FL (Fig. 18.3 ). Smaller areas of soils with ortstein occur in the Pacific
Northwest (OR and WA), New England-NY, and AK. There are at least three soil
series classified as Andisols that have ortstein-like horizons that are

<

50 % cemented
with Fe, Al, andMn. These include the Getchell, Hoquiam, and Hoko series, which are
classified as Haplocryands, Fulvudands, and Durudands, respectively. These series
account for 71,000 ha on the Olympic Peninsula of western WA.
Seven soil series with a placic horizon comprise 15,600 ha in HI, 8,600 ha in
western WA, and 1,700 ha in AK for a total area of 25,900 ha (Table 18.4 ). Two
additional soils contain thin, Fe-cemented horizons that could be recognized as
placic horizons, including the Copalis (Durudands) and Tokul (Vitrixerands) series,
which account for 100,000 ha in western WA. Soils with ortstein horizons and those
with placic horizons occur on the same landscape in only a few localities, such as
the Russian taiga (Karavayeva 1968 ) and southeastern Newfoundland (Lapen and
Wang 1999 ).

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