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| Titel |
Vertical and lateral particle and element fluxes across soil catenas in
southern Brazil |
| VerfasserIn |
Jerome Schoonejans, Veerle Vanacker, Sophie Opfergelt |
| Konferenz |
EGU General Assembly 2016
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250124362
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| Publikation (Nr.) |
 EGU/EGU2016-3784.pdf |
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| Zusammenfassung |
| At the Earth’s surface, mechanical disaggregation and chemical weathering transform
bedrock into mobile regolith and soil. Downslope translocation of weathering products by
lateral transport of soil particles and elements are determinant for the development of soil
catenas. To grasp the rates of soil formation and development along catenas, we need
better constraints on the vertical and lateral fluxes of particles and nutrients along
hillslopes.
Our study aims to analyze soil catena development in a spatio-temporal framework. The
data are collected in the central part of the Rio Grande do Sul State in southern Brazil. The
sampling area is located on the Serra Geral plateau composed by rhyodacite rocks
(∼700 m.a.s.l). The climate is humid subtropical (Cfa), and the natural vegetation
is characterized by deciduous tropical forest and native Araucaria angustifolia
forests.
Two soil catenas with different slope morphology were selected: a steep slope of 190m
long with maximum slope angle of 24˚ , and a gentle one of 140m long with a maximum
slope angle of 11˚ . In total, eight soil profiles were sampled and 67 soil and 8 saprock or
bedrock samples have been analysed for total element composition. Bulk densities were
determined on undisturbed soil samples. The soil thickness varies along catenas with soil
depths of about 90 cm on the ridge top, 30 cm on the convex nose of the steep slope and
>2 m on the foot slope. Chemical mass balance techniques are used to constrain
chemical weathering intensities (CDF) and absolute chemical mass losses or gains
(δj,w).
In each one of the eight soil profiles, we notice important absolute chemical mass losses
for the most mobile elements (Na, K and Ca). The mass transfer coefficients of Al
and Fe do not show a clear pattern, and largely depend on soil depth and position
along the soil catena. The weathering intensity of the soil and the absolute chemical
mass transfer are correlated with the residence time of the soil. Our data show a
systematic increase in chemical weathering intensity with distance from the ridge top. |
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