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| Titel |
Turnover of subsoil organic carbon controlled by substrate limitation and aggregation? |
| VerfasserIn |
Patrick Dietrich, Axel Don, Mirjam Helfrich |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250096826
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| Publikation (Nr.) |
 EGU/EGU2014-12349.pdf |
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| Zusammenfassung |
| Subsoils (>30 cm depth) store more than 50% of the total soil organic carbon (SOC) and
subsoil SOC is characterised by high mean residence times compared to topsoil SOC.
However, little is known about the mechanisms controlling the turnover of SOC in
the subsoil. The purpose of this study was to evaluate the effect of temperature,
substrate limitation and aggregation disturbance on subsoil SOC turnover. We assumed
that temperature limits SOC turnover in subsoil, but the temperature response of
SOC is obscured by an increasing stabilization of organic material with soil depth.
In a laboratory incubation experiment the production of CO2 from undisturbed
and disturbed soil samples and disturbed soil samples with added 13C labelled
roots were investigated at two different temperatures (10 and 20°C). Soil samples
were taken from 2-12 cm (depth 1), 30-60 cm (depth2) and 130-160 cm (depth 3)
in a deciduous forest from a podzolic Cambisol and were placed in microcosms
with an inner diameter of 14.2 cm and a height of 20 cm for depth 1 and 40 cm for
depth 2 and 3. The microcosms were incubated for 30 days at 60% of water holding
capacity.
The incubation experiment showed an average increase of 80-150% in CO2 production
for disturbed and undisturbed samples in depth 1 and depth 2 with increasing temperature.
However, this was not observed in depth 3. This temperature influence was not found in the
disturbed samples with added substrate. Instead, the increase in CO2 production of the
labelled samples from depth 2 and 3 had a lag time of 5 to 8 days compared to samples
from depth 1. Reasons for this delayed reaction on substrate might be dormant
microorganisms in the subsoil at the beginning of the incubation experiment or
spatial separation of microorganisms and the labelled substrate. Disturbance of the
samples from depth 1 and 2 initially increase the CO2 production, but this effect
was minor after day 15. Contrary to expectation, the CO2 production in depth 3
was greater in the undisturbed samples than in the disturbed samples, reasons for
that will be discussed. The factors controlling the SOC turnover in soils differs
between the topsoil and the subsoil and cannot be transferred from topsoil to subsoil. |
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