The Experts below are selected from a list of 36774 Experts worldwide ranked by ideXlab platform
Oliver A. Chadwick - One of the best experts on this subject based on the ideXlab platform.
-
Chemical transfers along slowly eroding Catenas developed on granitic cratons in southern Africa
Geoderma, 2013Co-Authors: Lesego Khomo, Carleton R. Bern, Anthony S. Hartshorn, Kevin H. Rogers, Oliver A. ChadwickAbstract:Abstract A catena is a series of distinct but co-evolving soils arrayed along a slope. On low-slope, slowly eroding Catenas the redistribution of mass occurs predominantly as plasma, the dissolved and suspended constituents in soil water. We applied mass balance methods to track how redistribution via plasma contributed to physical and geochemical differentiation of nine slowly eroding (~ 5 mm ky − 1 ) granitic Catenas. The Catenas were arrayed in a 3 × 3 climate by relief matrix and located in Kruger National Park, South Africa. Most of the Catenas contained at least one illuviated soil profile that had undergone more volumetric expansion and less mass loss, and these soils were located in the lower halves of the slopes. By comparison, the majority of slope positions were eluviated. Soils from the wetter climates (550 and 730 mm precipitation yr − 1 ) generally had undergone greater collapse and lost more mass, while soils in the drier climate (470 mm yr − 1 ) had undergone expansion and lost less mass. Effects of differences in catena relief were less clear. Within each climate zone, soil horizon mass loss and strain were correlated, as were losses of most major elements, illustrating the predominant influence of primary mineral weathering. Nevertheless, mass loss and volumetric collapse did not become extreme because of the skeleton of resistant primary mineral grains inherited from the granite. Colloidal clay redistribution, as traced by the ratio of Ti to Zr in soil, suggested clay losses via suspension from catena eluvial zones. Thus illuviation of colloidal clays into downslope soils may be crucial to catena development by restricting subsurface flow there. Our analysis provides quantitative support for the conceptual understanding of Catenas in cratonic landscapes and provides an endmember reference point in understanding the development of slowly eroding soil landscapes.
-
Impact of rainfall and topography on the distribution of clays and major cations in granitic Catenas of southern Africa
CATENA, 2011Co-Authors: Lesego Khomo, Anthony S. Hartshorn, Kevin H. Rogers, Oliver A. ChadwickAbstract:Abstract Soil Catenas integrate and amplify gravity transfer and differentiation processes of eluviation and illuviation in soil profiles. We quantified differences in these redistribution processes along granitic Catenas across an arid to sub-humid climate gradient in Kruger National Park, South Africa. We measured soil properties in nine Catenas sampled from three areas receiving annual rainfall of 470 mm (arid zone), 550 mm (semi-arid zone) and 730 mm (sub-humid zone). As rainfall increased, kaolinite replaced smectite as the dominant clay mineral in all landscape positions across the Catenas. Toeslopes showed the strongest evidence of this transition with an excess of smectite in the arid Catenas but complete prevalence of kaolinite in toeslopes of sub-humid Catenas. The concentration and distribution of clay along the Catenas were dependent on landscape position as well — soil profiles at and near the crests were clay depleted (as low as 1%) while those at the toeslopes had much more clay (up to 60%). Clay redistribution along Catenas was sensitive to climate with the least amount of redistribution occurring in the dry sites and the most occurring in the wet sites. As a consequence, the sub-humid Catenas had clay accumulation only in a small part of the toeslopes while the bulk of their length was represented by highly leached soils. In contrast, arid zone Catenas showed little clay redistribution and semi-arid sites displayed the greatest within-catena clay redistribution and preservation. Clay movement and storage conditioned other soil properties such as CEC, base cation distribution, base saturation and pH.
Lesego Khomo - One of the best experts on this subject based on the ideXlab platform.
-
Chemical transfers along slowly eroding Catenas developed on granitic cratons in southern Africa
Geoderma, 2013Co-Authors: Lesego Khomo, Carleton R. Bern, Anthony S. Hartshorn, Kevin H. Rogers, Oliver A. ChadwickAbstract:Abstract A catena is a series of distinct but co-evolving soils arrayed along a slope. On low-slope, slowly eroding Catenas the redistribution of mass occurs predominantly as plasma, the dissolved and suspended constituents in soil water. We applied mass balance methods to track how redistribution via plasma contributed to physical and geochemical differentiation of nine slowly eroding (~ 5 mm ky − 1 ) granitic Catenas. The Catenas were arrayed in a 3 × 3 climate by relief matrix and located in Kruger National Park, South Africa. Most of the Catenas contained at least one illuviated soil profile that had undergone more volumetric expansion and less mass loss, and these soils were located in the lower halves of the slopes. By comparison, the majority of slope positions were eluviated. Soils from the wetter climates (550 and 730 mm precipitation yr − 1 ) generally had undergone greater collapse and lost more mass, while soils in the drier climate (470 mm yr − 1 ) had undergone expansion and lost less mass. Effects of differences in catena relief were less clear. Within each climate zone, soil horizon mass loss and strain were correlated, as were losses of most major elements, illustrating the predominant influence of primary mineral weathering. Nevertheless, mass loss and volumetric collapse did not become extreme because of the skeleton of resistant primary mineral grains inherited from the granite. Colloidal clay redistribution, as traced by the ratio of Ti to Zr in soil, suggested clay losses via suspension from catena eluvial zones. Thus illuviation of colloidal clays into downslope soils may be crucial to catena development by restricting subsurface flow there. Our analysis provides quantitative support for the conceptual understanding of Catenas in cratonic landscapes and provides an endmember reference point in understanding the development of slowly eroding soil landscapes.
-
Impact of rainfall and topography on the distribution of clays and major cations in granitic Catenas of southern Africa
CATENA, 2011Co-Authors: Lesego Khomo, Anthony S. Hartshorn, Kevin H. Rogers, Oliver A. ChadwickAbstract:Abstract Soil Catenas integrate and amplify gravity transfer and differentiation processes of eluviation and illuviation in soil profiles. We quantified differences in these redistribution processes along granitic Catenas across an arid to sub-humid climate gradient in Kruger National Park, South Africa. We measured soil properties in nine Catenas sampled from three areas receiving annual rainfall of 470 mm (arid zone), 550 mm (semi-arid zone) and 730 mm (sub-humid zone). As rainfall increased, kaolinite replaced smectite as the dominant clay mineral in all landscape positions across the Catenas. Toeslopes showed the strongest evidence of this transition with an excess of smectite in the arid Catenas but complete prevalence of kaolinite in toeslopes of sub-humid Catenas. The concentration and distribution of clay along the Catenas were dependent on landscape position as well — soil profiles at and near the crests were clay depleted (as low as 1%) while those at the toeslopes had much more clay (up to 60%). Clay redistribution along Catenas was sensitive to climate with the least amount of redistribution occurring in the dry sites and the most occurring in the wet sites. As a consequence, the sub-humid Catenas had clay accumulation only in a small part of the toeslopes while the bulk of their length was represented by highly leached soils. In contrast, arid zone Catenas showed little clay redistribution and semi-arid sites displayed the greatest within-catena clay redistribution and preservation. Clay movement and storage conditioned other soil properties such as CEC, base cation distribution, base saturation and pH.
Kevin H. Rogers - One of the best experts on this subject based on the ideXlab platform.
-
Chemical transfers along slowly eroding Catenas developed on granitic cratons in southern Africa
Geoderma, 2013Co-Authors: Lesego Khomo, Carleton R. Bern, Anthony S. Hartshorn, Kevin H. Rogers, Oliver A. ChadwickAbstract:Abstract A catena is a series of distinct but co-evolving soils arrayed along a slope. On low-slope, slowly eroding Catenas the redistribution of mass occurs predominantly as plasma, the dissolved and suspended constituents in soil water. We applied mass balance methods to track how redistribution via plasma contributed to physical and geochemical differentiation of nine slowly eroding (~ 5 mm ky − 1 ) granitic Catenas. The Catenas were arrayed in a 3 × 3 climate by relief matrix and located in Kruger National Park, South Africa. Most of the Catenas contained at least one illuviated soil profile that had undergone more volumetric expansion and less mass loss, and these soils were located in the lower halves of the slopes. By comparison, the majority of slope positions were eluviated. Soils from the wetter climates (550 and 730 mm precipitation yr − 1 ) generally had undergone greater collapse and lost more mass, while soils in the drier climate (470 mm yr − 1 ) had undergone expansion and lost less mass. Effects of differences in catena relief were less clear. Within each climate zone, soil horizon mass loss and strain were correlated, as were losses of most major elements, illustrating the predominant influence of primary mineral weathering. Nevertheless, mass loss and volumetric collapse did not become extreme because of the skeleton of resistant primary mineral grains inherited from the granite. Colloidal clay redistribution, as traced by the ratio of Ti to Zr in soil, suggested clay losses via suspension from catena eluvial zones. Thus illuviation of colloidal clays into downslope soils may be crucial to catena development by restricting subsurface flow there. Our analysis provides quantitative support for the conceptual understanding of Catenas in cratonic landscapes and provides an endmember reference point in understanding the development of slowly eroding soil landscapes.
-
Impact of rainfall and topography on the distribution of clays and major cations in granitic Catenas of southern Africa
CATENA, 2011Co-Authors: Lesego Khomo, Anthony S. Hartshorn, Kevin H. Rogers, Oliver A. ChadwickAbstract:Abstract Soil Catenas integrate and amplify gravity transfer and differentiation processes of eluviation and illuviation in soil profiles. We quantified differences in these redistribution processes along granitic Catenas across an arid to sub-humid climate gradient in Kruger National Park, South Africa. We measured soil properties in nine Catenas sampled from three areas receiving annual rainfall of 470 mm (arid zone), 550 mm (semi-arid zone) and 730 mm (sub-humid zone). As rainfall increased, kaolinite replaced smectite as the dominant clay mineral in all landscape positions across the Catenas. Toeslopes showed the strongest evidence of this transition with an excess of smectite in the arid Catenas but complete prevalence of kaolinite in toeslopes of sub-humid Catenas. The concentration and distribution of clay along the Catenas were dependent on landscape position as well — soil profiles at and near the crests were clay depleted (as low as 1%) while those at the toeslopes had much more clay (up to 60%). Clay redistribution along Catenas was sensitive to climate with the least amount of redistribution occurring in the dry sites and the most occurring in the wet sites. As a consequence, the sub-humid Catenas had clay accumulation only in a small part of the toeslopes while the bulk of their length was represented by highly leached soils. In contrast, arid zone Catenas showed little clay redistribution and semi-arid sites displayed the greatest within-catena clay redistribution and preservation. Clay movement and storage conditioned other soil properties such as CEC, base cation distribution, base saturation and pH.
Anthony S. Hartshorn - One of the best experts on this subject based on the ideXlab platform.
-
Chemical transfers along slowly eroding Catenas developed on granitic cratons in southern Africa
Geoderma, 2013Co-Authors: Lesego Khomo, Carleton R. Bern, Anthony S. Hartshorn, Kevin H. Rogers, Oliver A. ChadwickAbstract:Abstract A catena is a series of distinct but co-evolving soils arrayed along a slope. On low-slope, slowly eroding Catenas the redistribution of mass occurs predominantly as plasma, the dissolved and suspended constituents in soil water. We applied mass balance methods to track how redistribution via plasma contributed to physical and geochemical differentiation of nine slowly eroding (~ 5 mm ky − 1 ) granitic Catenas. The Catenas were arrayed in a 3 × 3 climate by relief matrix and located in Kruger National Park, South Africa. Most of the Catenas contained at least one illuviated soil profile that had undergone more volumetric expansion and less mass loss, and these soils were located in the lower halves of the slopes. By comparison, the majority of slope positions were eluviated. Soils from the wetter climates (550 and 730 mm precipitation yr − 1 ) generally had undergone greater collapse and lost more mass, while soils in the drier climate (470 mm yr − 1 ) had undergone expansion and lost less mass. Effects of differences in catena relief were less clear. Within each climate zone, soil horizon mass loss and strain were correlated, as were losses of most major elements, illustrating the predominant influence of primary mineral weathering. Nevertheless, mass loss and volumetric collapse did not become extreme because of the skeleton of resistant primary mineral grains inherited from the granite. Colloidal clay redistribution, as traced by the ratio of Ti to Zr in soil, suggested clay losses via suspension from catena eluvial zones. Thus illuviation of colloidal clays into downslope soils may be crucial to catena development by restricting subsurface flow there. Our analysis provides quantitative support for the conceptual understanding of Catenas in cratonic landscapes and provides an endmember reference point in understanding the development of slowly eroding soil landscapes.
-
Impact of rainfall and topography on the distribution of clays and major cations in granitic Catenas of southern Africa
CATENA, 2011Co-Authors: Lesego Khomo, Anthony S. Hartshorn, Kevin H. Rogers, Oliver A. ChadwickAbstract:Abstract Soil Catenas integrate and amplify gravity transfer and differentiation processes of eluviation and illuviation in soil profiles. We quantified differences in these redistribution processes along granitic Catenas across an arid to sub-humid climate gradient in Kruger National Park, South Africa. We measured soil properties in nine Catenas sampled from three areas receiving annual rainfall of 470 mm (arid zone), 550 mm (semi-arid zone) and 730 mm (sub-humid zone). As rainfall increased, kaolinite replaced smectite as the dominant clay mineral in all landscape positions across the Catenas. Toeslopes showed the strongest evidence of this transition with an excess of smectite in the arid Catenas but complete prevalence of kaolinite in toeslopes of sub-humid Catenas. The concentration and distribution of clay along the Catenas were dependent on landscape position as well — soil profiles at and near the crests were clay depleted (as low as 1%) while those at the toeslopes had much more clay (up to 60%). Clay redistribution along Catenas was sensitive to climate with the least amount of redistribution occurring in the dry sites and the most occurring in the wet sites. As a consequence, the sub-humid Catenas had clay accumulation only in a small part of the toeslopes while the bulk of their length was represented by highly leached soils. In contrast, arid zone Catenas showed little clay redistribution and semi-arid sites displayed the greatest within-catena clay redistribution and preservation. Clay movement and storage conditioned other soil properties such as CEC, base cation distribution, base saturation and pH.
Peter W. Birkeland - One of the best experts on this subject based on the ideXlab platform.
-
Variation in Soil-Catena Characteristics of Moraines with Time and Climate, South Island, New Zealand
Quaternary Research, 1994Co-Authors: Peter W. BirkelandAbstract:Abstract Soil Catenas on three moraines in each of two areas with different climate were studied to determine (a) downcatena soil differentiation with climate and time and (b) their usefulness in estimating the relative ages of the underlying deposits. In the dry area (mean annual precipitation (MAP), ca. 0.5 m) all soils have A/Bw/C profiles formed in loess/till. Their similarity in morphology and in most chemical characteristics with catena position and age suggests that the low MAP does not result in much redistribution of water, elements, or sediment downcatena. This similarity also suggests ages close to each other and correlation with the Otiran Glaciation (oxygen-isotope stages 2 and 4). In the wet area (MAP ca. 3 m) the soils also formed in loess/till and with time (a) soil morphology progresses from A/Bw/C to A/E/B/C, (h) reduced properties intensify, especially in the downcatena profiles, (c) citrate-bicarbonate-dithionite-extractable Fe displays accumulation in the youngest catena followed by loss in the older Catenas, and (d) downcatena trends in total chemical data display marked losses of the more mobile elements. These data demonstrate that although catena development is rapid in a wet climate, the downcatena contrast can be muted with time due to a change from processes dominated by oxidation to those dominated by reduction. Soil catena properties in the wet area are sufficiently different to not refute age estimations suggested by Suggate (1990): youngest moraine, oxygen-isotope stage 2; intermediate moraine, isotope stage 4; and oldest moraine, isotope stage 10. An unresolved problem in both areas is the possibility of soil erosion to foul soil-age relations.
-
Soil-catena development with time in a hot desert, southern Israel—field data and salt distribution
Journal of Arid Environments, 1991Co-Authors: Peter W. Birkeland, Ran GersonAbstract:Four soil Catenas on alluvial-terrace scarps and bar-and-swale topography of alluvial deposits have been studied in southern Israel to determine the influence of time and slope position on soil development. The approximate ages of the Catenas are: middle Holocene, early Holocene to latest Pleistocene, younger late Pleistocene, and old late Pleistocene to middle Pleistocene. Most of the trends in soil development seem best related to the age of the surface. The youngest soils are Av/Btjyj/Byj profiles and the older ones are Av/Bt or Bty/Byzm profiles. The best trends with time are the development and thickness of the Bt horizon and the development of a cemented salt horizon. Few trends are solely related to the position of a soil within a catena, except that the footslope soil of the oldest catena has a cumulic Bt horizon. This suggests that erosion–deposition processes since the inception of soil formation have been relatively minor on most slopes. Salt accumulation is progressive only in the three youngest Catenas but the trend does not continue for the oldest catena, perhaps because of some combination of climatic change and decreasing soil-water infiltration capacity with time.
-
Use of soil catena field data for estimating relative ages of moraines
Geology, 1991Co-Authors: Peter W. Birkeland, Margaret E. Berry, David K. SwansonAbstract:Soils at the crests of moraines are commonly used to estimate the relative ages of moraines. However, for various pedologic and geomorphic reasons, soil development at crest sites may not truly reflect the time since moraine formation; for example, some crest soils on moraines of greatly different age are similar in morphology and development. Soil catena data for soils at several sites aligned downslope from the crest can greatly improve on the usefulness of soil data for estimating moraine ages. For this purpose, the authors use the weighted mean catena profile development index, which condenses field data for all of the soils in each catena into a single value.