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| Titel |
The influence of C3 and C4 vegetation on soil organic matter dynamics in contrasting semi-natural tropical ecosystems |
| VerfasserIn |
G. Saiz, M. Bird, C. Wurster, C. A. Quesada, P. Ascough, T. Domingues, F. Schrodt, M. Schwarz, T. R. Feldpausch, E. Veenendaal, G. Djagbletey, G. Jacobsen, F. Hien, H. Compaore, A. Diallo, J. Lloyd |
| 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. 16 ; Nr. 12, no. 16 (2015-08-26), S.5041-5059 |
| Datensatznummer |
250118074
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| Publikation (Nr.) |
 copernicus.org/bg-12-5041-2015.pdf |
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| Zusammenfassung |
| Variations in the carbon isotopic composition of soil organic matter (SOM)
in bulk and fractionated samples were used to assess the influence of
C3 and C4 vegetation on SOM dynamics in semi-natural tropical
ecosystems sampled along a precipitation gradient in West Africa.
Differential patterns in SOM dynamics in C3/C4 mixed ecosystems
occurred at various spatial scales. Relative changes in C / N ratios between
two contrasting SOM fractions were used to evaluate potential site-scale
differences in SOM dynamics between C3- and C4-dominated
locations. These differences were strongly controlled by soil texture across
the precipitation gradient, with a function driven by bulk δ13C
and sand content explaining 0.63 of the observed variability. The variation
of δ13C with soil depth indicated a greater accumulation of
C3-derived carbon with increasing precipitation, with this trend also
being strongly dependant on soil characteristics. The influence of
vegetation thickening on SOM dynamics was also assessed in two adjacent, but
structurally contrasting, transitional ecosystems occurring on comparable
soils to minimise the confounding effects posed by climatic and edaphic
factors. Radiocarbon analyses of sand-size aggregates yielded relatively
short mean residence times (τ) even in deep soil layers, while the
most stable SOM fraction associated with silt and clay exhibited shorter
τ in the savanna woodland than in the neighbouring forest stand. These
results, together with the vertical variation observed in δ13C
values, strongly suggest that both ecosystems are undergoing a rapid
transition towards denser closed canopy formations. However, vegetation
thickening varied in intensity at each site and exerted contrasting effects
on SOM dynamics. This study shows that the interdependence between biotic
and abiotic factors ultimately determine whether SOM dynamics of C3-
and C4-derived vegetation are at variance in ecosystems where both
vegetation types coexist. The results highlight the far-reaching
implications that vegetation thickening may have for the stability of deep
SOM. |
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