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Titel |
Distinct patterns in the diurnal and seasonal variability in four components of soil respiration in a temperate forest under free-air CO2 enrichment |
VerfasserIn |
L. Taneva, M. A. Gonzalez-Meler |
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 ; 8, no. 10 ; Nr. 8, no. 10 (2011-10-31), S.3077-3092 |
Datensatznummer |
250006175
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Publikation (Nr.) |
copernicus.org/bg-8-3077-2011.pdf |
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Zusammenfassung |
Soil respiration (RS) is a major flux in the global carbon (C) cycle.
Responses of RS to changing environmental conditions may exert a strong
control on the residence time of C in terrestrial ecosystems and in turn
influence the atmospheric concentration of greenhouse gases. Soil
respiration consists of several components oxidizing soil C from different
pools, age and chemistry. The mechanisms underlying the temporal variability
of RS components are poorly understood. In this study, we used the
long-term whole-ecosystem 13C tracer at the Duke Forest Free Air
CO2 Enrichment site to separate forest RS into its autotrophic
(RR) and heterotrophic components (RH). The contribution of
RH to RS was further partitioned into litter decomposition
(RL), and decomposition of soil organic matter (RSOM) of two age
classes – up to 8 yr old and SOM older than 8 yr. Soil respiration was
generally dominated by RSOM during the growing season (44% of
daytime RS), especially at night. The contribution of heterotrophic
respiration (RSOM and RL) to RS was not constant, indicating
that the seasonal variability in RR alone cannot explain seasonal
variation in RS. Although there was no diurnal variability in RS,
there were significant compensatory differences in the contribution of
individual RS components to daytime and nighttime rates. The average
contribution of RSOM to RS was greater at night (54%) than
during the day (44%). The average contribution of RR to total
RS was ~30% during the day and ~34% during the night.
In contrast, RL constituted 26% of RS during the day and only
12% at night. About 95% of the decomposition of soil C older than 8 yr
(Rpre-tr) originated from RSOM and showed more pronounced
and consistent diurnal variability than any other RS component;
nighttime rates were on average 29% higher than daytime rates. In
contrast, the decomposition of more recent, post-treatment C (Rpre-tr)
did not vary diurnally. None of the diurnal variations in components of
RH could be explained by only temperature and moisture variations. Our
results indicate that the variation observed in the components of RS is
the result of complex interaction between dominant biotic controls (e.g. plant
activity, mineralization kinetics, competition for substrates) over abiotic
controls (temperature, moisture). The interactions and controls among roots
and other soil organisms that utilize C of different chemistry,
accessibility and ages, results in the overall soil CO2 efflux.
Therefore understanding the controls on the components of RS is
necessary to elucidate the influence of ecosystem respiration on atmospheric
C-pools at different time scales. |
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