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| Titel |
Using O2 to study the relationships between soil CO2 efflux and soil respiration |
| VerfasserIn |
A. Angert, D. Yakir, M. Rodeghiero, Y. Preisler, E. A. Davidson, T. Weiner |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1726-4170
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| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 12, no. 7 ; Nr. 12, no. 7 (2015-04-07), S.2089-2099 |
| Datensatznummer |
250117889
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| Publikation (Nr.) |
 copernicus.org/bg-12-2089-2015.pdf |
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| Zusammenfassung |
| Soil respiration is the sum of respiration processes in the soil and is a
major flux in the global carbon cycle. It is usually assumed that the
CO2 efflux is equal to the soil respiration rate. Here we challenge
this assumption by combining measurements of CO2 with high-precision
measurements of O2. These measurements were conducted on different
ecosystems and soil types and included measurements of air samples taken
from the soil profile of three Mediterranean sites: a temperate forest and
two alpine forests. Root-free soils from the alpine sites were also
incubated in the lab. We found that the ratio between the CO2 efflux
and the O2 influx (defined as apparent respiratory quotient, ARQ) was
in the range of 0.14 to 1.23 and considerably deviated from the value of
0.9 ± 0.1 expected from the elemental composition of average plants and
soil organic matter. At the Mediterranean sites, these deviations are
explained as a result of CO2 dissolution in the soil water and
transformation to bicarbonate ions in these high-pH soils, as well as by carbonate
mineral dissolution and precipitation processes. Thus, a correct estimate of
the short-term, chamber-based biological respiratory flux in such soils can
only be made by dividing the measured soil CO2 efflux by the average
(efflux-weighted) soil profile ARQ. Applying this approach to a semiarid
pine forest resulted in an estimated short-term biological respiration rate
that is 3.8 times higher than the chamber-measured surface CO2. The ARQ
values often observed in the more acidic soils were unexpectedly low
(< 0.7). These values probably result from the oxidation of reduced
iron, which has been formed previously during times of high soil moisture
and local anaerobic conditions inside soil aggregates. The results reported
here provide direct quantitative evidence of a large temporal decoupling
between soil–gas exchange fluxes and biological soil respiration. |
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