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| Titel |
Large fluxes and rapid turnover of mineral-associated carbon across topographic gradients in a humid tropical forest: insights from paired 14C analysis |
| VerfasserIn |
S. J. Hall, G. McNicol, T. Natake, W. L. Silver |
| 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. 8 ; Nr. 12, no. 8 (2015-04-29), S.2471-2487 |
| Datensatznummer |
250117914
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| Publikation (Nr.) |
 copernicus.org/bg-12-2471-2015.pdf |
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| Zusammenfassung |
| It has been proposed that the large soil carbon (C) stocks of humid tropical
forests result predominantly from C stabilization by reactive minerals,
whereas oxygen (O2) limitation of decomposition has received much less
attention. We examined the importance of these factors in explaining
patterns of C stocks and turnover in the Luquillo Experimental Forest,
Puerto Rico, using radiocarbon (14C) measurements of contemporary and
archived samples. Samples from ridge, slope, and valley positions spanned
three soil orders (Ultisol, Oxisol, Inceptisol) representative of humid
tropical forests, and differed in texture, reactive metal content, O2
availability, and root biomass. Mineral-associated C comprised the large
majority (87 ± 2%, n = 30) of total soil C. Turnover of most
mineral-associated C (66 ± 2%) was rapid (11 to 26 years; mean and
SE: 18 ± 3 years) in 25 of 30 soil samples across surface horizons (0–10
and 10–20 cm depths) and all topographic positions, independent of
variation in reactive metal concentrations and clay content. Passive C with
centennial–millennial turnover was typically much less abundant (34 ± 3%), even at 10–20 cm depths. Carbon turnover times and
concentrations significantly increased with concentrations of reduced iron
(Fe(II)) across all samples, suggesting that O2 availability may have
limited the decomposition of mineral-associated C over decadal scales.
Steady-state inputs of mineral-associated C were statistically similar among
the three topographic positions, and could represent 10–25% of annual
litter production. Observed trends in mineral-associated Δ14C
over time could not be fit using the single-pool model used in many other
studies, which generated contradictory relationships between turnover and
Δ14C as compared with a more realistic two-pool model. The
large C fluxes in surface and near-surface soils documented here are
supported by findings from paired 14C studies in other types of
ecosystems, and suggest that most mineral-associated C cycles relatively
rapidly (decadal scales) across ecosystems that span a broad range of state
factors. |
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