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| Titel |
Interaction between soil formation and geomorphic dynamics along a soil catena in the Turbolo watershed (northwest Calabria, southern Italy) |
| VerfasserIn |
Fabio Scarciglia, Massimo Conforti, Pietro P. C. Aucelli, Gaetano Robustelli, Giuseppe Palumbo |
| Konferenz |
EGU General Assembly 2010
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250037417
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| Zusammenfassung |
| This work focuses on the analysis of a soil catena located along a slope in the Turbolo
watershed in northwest Calabria, southern Italy. This geomorphological context can be
assumed as representative of widespread sites in the same region, as well as of several zones
in the Mediterranean area, on the basis of its variegate but common lithological, topographic,
pedological and climatic features, on the whole prone to high soil erosion susceptibility. The
Turbolo stream is a tributary of the Crati river, covers an area of about 30 km2 and develops
longitudinally from west to east up to about 13 km in length. It originates from
the eastern flank of the Coastal Range and ranges from more than 1000 m to 75
m asl. The watershed is developed through Palaeozoic metamorphic rocks in the
western sector, where high relief and steep slopes dominate, whereas the eastern hilly
reaches are characterised by gentler slopes and terraces cut on sedimentary terrains
of Neogene-Quaternary ages. The soil toposequence we analysed consists of six
soil profiles in the eastern sector, on a north-facing slope, cut across Pleistocene
marine silty clays, comprised between 85 to 140 m asl in elevation and 5 to 20Ë
inclined.
Field observations, chemical-physical data and micromorphological features contribute
interesting considerations in the understanding of the interplay between soil-forming
processes and geomorphic dynamics. At present, the land is uncultivated with sparse
olive trees and is mainly affected by sheet wash and rill erosion, with poor gully
incision in places. These processes are presumably promoted by the recent abandon of
agricultural crops in the last decade and by the slight local relief of the footslope
(about 3 m) above the Turbolo valley-floor, whose main channel occurs less than 100
m far. The selected soil profiles represent loam to (sandy-)clay-loam Inceptisols
characterised by accumulation of organic matter (always > 2% except in one profile) in
topsoils, neutral to strongly alkaline reaction, granular to (sub)angular blocky (to
prismatic) structure, some vertic properties, poor CaCO3 dynamics, and pseudogley
features in deep horizons indicating transient aquic moisture regime (seasonally
saturated) and fluctuating water-table. The soils consist of variable combinations of
most or few of these genetic horizons: Ap1-Ap2-BA-Bw-Bg1-Bg2. The variable
juxtaposition of such horizons, along with wavy to irregular, sharp to abrupt lower
boundaries and variable thickness of surface Ap horizons (completely lacking in one
upslope soil profile of the catena and doubled in the lowermost one), clearly testify for
the influence of past agricultural activities, soil erosion and colluviation. On the
whole, reworked soil accumulation prevails at the slope bottom, whereas erosion is
severer upslope, as also evidenced by the overall decrease of carbonate reaction
and total CaCO3 content downslope. This result is consistent with the occurrence
of some small carbonate concretions in surface or upper subsoil horizons in the
intermediate-upper soil profiles. The micromorphological analysis of thin sections from
undisturbed soil samples confirmed the presence of carbonate concretions, hydromorphic
features (Fe-Mn segregations and iron-depleted zones), anisotropic clay domains
(observed between crossed polars) representing stress features due to vertic dynamics,
and highlighted occasional clay coatings emplaced by relict illuviation processes.
Moreover, topsoils exhibit variably aerated, highly porous structures with frequent
evidence of bioturbation and likely anthropogenic disturbance. Some centimetre-thick
surface crusts occur, especially in one soil profile along the lower-intermediate slope
segment, where subhorizontal, upward-concave, laminar aggregates separated by
submillimetric to 1-2 mm thick cracks, were identified. Mercury intrusion porosimetry
performed on topsoil samples revealed slight changes in percentages of intra-aggregate
microporosity, but very variable pore size distribution and extremely different permeability. |
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