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| Titel |
Soil production rates on silicate parent material in high-mountains: different approaches - different results? |
| VerfasserIn |
Markus Egli, Dennis Dahms, Kevin Norton |
| Konferenz |
EGU General Assembly 2013
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 15 (2013) |
| Datensatznummer |
250079543
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| Zusammenfassung |
| High-mountain soils develop in particularly sensitive environments. Consequently,
deciphering and predicting what drives the rates of soil formation in such environments is a
major challenge. In terms of soil production from chemical weathering, the predominating
perception for high-mountain soils and cold environments often is that the chemical
weathering ‘portion’ of soil development is temperature-inhibited, often to the point of
non-occurrence. Several concepts exist to determine long-term rates of soil formation and
development. We present three different approaches: (1) quantification of soil formation from
minimally eroded soils of known age using chronosequences (known surface age and soil
thickness - SAST), (2) determination of soil residence times (SRT) and production
rates through chemical weathering using (un)stable isotopes (e.g. 230Th / 234U
activity ratios), and (3) a steady state approach using cosmogenic isotopes (e.g.
10Be).
Data form different climate zones, and particularly from high-mountains (alpine
environment), were compared. The SAST and steady state approach gave quite similar
results for alpine environments (European Alps and the Wind River Range (Rocky
Mountains USA)). Soil formation rates in mountain areas (but having a temperate
climate) using the SRT approach, did not differ greatly from the SAST and Steady
State approaches. Independent of the chosen approach, the results seem moderately
comparable. Soil formation rates in high-mountain areas (alpine climate) ranged
from very low to extremely high values and showed a clear decreasing tendency
with time. Very young soils have up to 3 – 4 orders of magnitude higher rates of
development than old soils (105 to 106 years). This is due to the fact that weathering
is kinetically limited in regions having young surfaces and supply limited on old
surfaces.
Soil production rates cannot be infinitely high. Consequently, a speed limit must
exist. In the literature, this limit has been set at about 320 to 450 t km-2 yr-1. Our
results show, however, that in alpine areas soil formation easily reaches rates of up to
1000 – 3000 t km-2 yr-1 using the SAST approach. These data are consistent with
previous studies in mountain regions demonstrating that soils continue to develop
with time, even under continuous seasonal snowpack and, thus, that the concept
of ‘temperature-controlled’ soil development (soil-forming intervals) is spurious. |
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