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| Titel |
Hydropedological model of vertisol formation along the Gulf Coast Prairie land resource area of Texas |
| VerfasserIn |
L. C. Nordt, S. G. Driese |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1027-5606
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| Digitales Dokument |
URL |
| Erschienen |
In: Hydrology and Earth System Sciences ; 13, no. 11 ; Nr. 13, no. 11 (2009-11-03), S.2039-2053 |
| Datensatznummer |
250012047
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| Publikation (Nr.) |
 copernicus.org/hess-13-2039-2009.pdf |
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| Zusammenfassung |
| Vertisols are clayey soils containing slickensides and wedge-shaped
aggregates formed by shrink-swell processes in seasonally wet climates. The
dynamic distribution of macro- and microvoids as a by-product of this unique
pedoturbation process, accompanied by microtopographic lows and highs
(gilgai), mitigate our ability to make accurate and precise interpretations
of aquic and hydric conditions in these problem soils. We studied Vertisols
across a subhumid to humid climosequence to assess the formation of
redoximorphic features on shallow, linear (nondepressional) landscape
positions in response to varying levels of rainfall. Approximately 1000 mm
of mean annual precipitation (MAP) is required to form soft iron masses that
then increase in abundance, and to shallower depths, with increasing
rainfall. Soft iron masses with diffuse boundaries become more abundant with
higher rainfall in microlows, whereas masses with nondiffuse boundaries
become more common in microhighs. Most soft iron masses form in oxygenated
ped interiors as water first saturates and then reduces void walls where
iron depletions form. In contrast, at least 1276 mm of MAP is needed to form
iron pore linings in both microlow and microhigh topographic positions. Iron
depletions do not correlate with rainfall in terms of abundance or depth of
occurrence. The quantity of crayfish burrows co-varies with rainfall and
first appears coincidentally with soft iron masses in microlows near 1000 mm
of MAP; they do not appear until nearly 1400 mm of MAP in microhighs.
Dithionite-citrate extractable and ammonium-oxalate extractable iron oxides
increase systematically with rainfall indicating more frequent episodes of
iron reduction and precipitation into pedogenic segregations. The sum of our
data suggests that Vertisols forming in the Coast Prairie of Texas with MAP
greater than 1276 mm should be classified as aquerts because of the presence
of aquic conditions. These same soils may also meet the definition of hydric
as one criterion for the identification of Federally-protected wetlands.
However, there is a considerable disjunct between protracted periods of
saturation and limited periods of reduction in these soils. Based on the
distribution of redoximorphic features in the study area, regional water
table data, and recent electrical resistivity data from a nearby upland
Vertisol, non-Darcian bypass flow is the principle mechanism governing the
flux of water through deep cracks where water first accumulates and then
persists in microlow bowls at depths of 1 to 2 m. |
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