Fragipan Horizon - Soil Geography of the USA: A Diagnostic-Horizon Approach - page 157

Table 15.3 Relation of soil-forming factors to the development of fragipans (Bockheim and
Hartemink 2013 )
Area Soil taxa Role of soil-forming factor Citations

Climate

USA 361 soil series 75 % of fragic soils have udic

soil-moisture regime

This study

Eastern
USA

- Fragic soils occur in areas

where precipitation

Grossman and
Carlisle ( 1969 )

>

evaporation

Eastern
USA

- Fragic soils occur primarily in

forested areas

Grossman and
Carlisle ( 1969 )

Relief

IL Oxyaquic Fragiudalfs Fragic soils occur in depres-

sions with restricted
drainage

Grossman
et al. ( 1959a , b , c )

PA 201 soil series Ciolkosz et al. ( 1992 )

Midwest
USA

- Fragic soils occur primarily on

slopes < 12 %

Franzmeier
et al. ( 1989 )

Parent materials

361 pedons Fragic soils occur especially in

areas with loess and
low-lime till

This study

NY Oxyaquic Fragiudalfs Grossman

et al. ( 1959a , b , c )

PA 200+ pedons Fragic soils occur mainly in

loam and silt-loam textural
classes

Petersen et al. ( 1970
and Ciolkosz
et al. ( 1992 )

USA 361 soil series This study

MO Fragipans form especially in

soils with paralithic/lithic
contacts

James et al. ( 1995 )

MO Aide and Marshaus

( 2002 )

OH Aeric Fragiaqualfs,

Oxyaquic Fragiudalfs,
Typic Fragiudults

Fragipans form especially in
soils with lithological
discontinuities

Smeck et al. ( 1989 )

WI Aquic Fragiochrepts Habecker et al. ( 1990 )

MI Alfic Oxyaquic Fragiorthods Bockheim ( 2003 )

IL Oxyaquic Hapludalfs Wilson et al. ( 2010 )

Time

PA - Fragic soils require a minimum

of 18 ky to form

Ciolkosz et al. ( 1992 )

forest-prairie boundary. They also noted that fragipans appear to be restricted to
areas where precipitation exceeds evaporation for much of the year. The mecha-
nisms in which trees play in the genesis of fragic soil materials remain largely
unclear. Franzmeier et al. ( 1989 ) suggested that evapotranspiration by hardwood
trees (dicots), which are prevalent in areas with fragipan soils, may increase silica in
the soil solution to a greater extent than grasses; this would account for the fact that
fragipans are seldom found in soils under prairie vegetation.