Genesis of pedons with discontinuous argillic horizons in the Holocene loess mantle of the southern Pampean landscape,Argentina |
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| Institution: | 1. Kansai Research Center, Forestry and Forest Products Research Institute, Nagai-kyutaro, Momoyama, Fushimi, Kyoto 612-0855, Japan;2. Department of Bioapplications and Systems Engineering (BASE), Tokyo University of Agriculture and Technology, 2-24-16 Koganei, Tokyo 184-8588, Japan;3. National Institute for Agro-Environmental Sciences, 3-1-3 Kannondai, Tsukuba, Ibaraki 305-8604, Japan;4. Atomic & Molecular Physics Laboratory, Institute for Chemical Research, Kyoto University, Gokasho, Uji, Kyoto 611-0011, Japan;5. Surface Chemical Analysis G., National Institute for Materials Science, 1-2-1 Sengen, Tsukuba-shi, Ibaraki 305-0047, Japan;6. Laboratory of Advanced Science and Technology for Industry, University of Hyogo, 3-1-2 Koto, Kamigori-cho, Ako-gun, Hyogo 678-1205, Japan;7. Synchrotron Analysis L.L.C., 3-1-2 Koto, Kamigori-cho, Ako-gun, Hyogo 678-1205, Japan;8. Forestry and Forest Products Research Institute, Matsunosato, Tsukuba, Ibaraki 305-8687, Japan;1. Department of Forest Ecology, The Silva Tarouca Research Institute for Landscape and Ornamental Gardening, Lidická 25/27, 602 00 Brno, Czech Republic;2. Department of Geography, Michigan State University, 128 Geography Building, East Lansing, MI 48824, USA;3. Department of Forest Botany, Dendrology and Geobiocoenology, Faculty of Forestry and Wood Technology, Mendel University in Brno, Zemedelska 1, 613 00 Brno, Czech Republic;4. Department of Botany and Zoology, Faculty of Science, Masaryk University, Kotlá?ská 267/2, 611 37 Brno, Czech Republic;5. Department of Soil Science and Soil Protection, The Faculty of Agrobiology, Food and Natural Resources, Czech University of Life Sciences Prague, Kamýcká 129, 165 21 Praha 6, Czech Republic |
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| Abstract: | Soil development in the plain landscape of the southern Argentinean Pampa is related to pulses of aeolian accretion of calcareous loess during the Holocene epoch. Such plain relief is associated with landform stability that favors pedogenesis. In some sectors of the Holocene loess mantle, detailed soil surveys show a great variability of soil morphology in short distances (<7 m), such that pedons with Bt horizon (Ap-Bt-C-2Ckm) coexist with pedons with an AC horizon (Ap-AC-C-2Ckm) in a plain landscape, within identical loess parent material over a tosca layer (2Ckm-calcrete-petrocalcic horizon), and in a similar pedoclimate. This article studies the origin of this spatial variation. Loess parent materials directly overlie the relic tosca layer, exhumed after erosion of preexisting soils of the Late Pleistocene. The contrast in soil morphology between the petrocalcic horizon and the overlying Holocene soils reflects the effect of polygenesis. The complex soil spatial distribution pattern over the tosca layer appears unrelated to its paleomicrotopography, because soils with Bt horizons are identified in positive and depressed microlandforms of the tosca. The absence of Bt horizons might be caused by formerly intense biological activity related to a stable pattern of two natural vegetation covers or a surface paleomicrotopography that supported distinct vegetation types depending on the soil moisture in each paleomicrolandform. |
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