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| Titel |
The influence of C3 and C4 vegetation on SOM dynamics across contrasting semi-natural ecosystems in West Africa |
| VerfasserIn |
Gustavo Saiz, Michael Bird, Elmar Veeenendaal, Franziska Schrodt, Tomas Domingues, Ted Feldpausch, Jonathan Lloyd |
| Konferenz |
EGU General Assembly 2015
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250107687
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| Publikation (Nr.) |
 EGU/EGU2015-7399.pdf |
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| Zusammenfassung |
| A progressive ‘thickening’ of woody vegetation in tropical grasslands and savannas is a
widespread phenomenon being promoted by increasing atmospheric CO2 concentrations,
climate change, variations in fire regimes and other human-related activities such as
intensified grazing. The impact of these vegetation dynamics on ecosystem biogeochemistry
and the global carbon cycle may be highly significant given the large extent of grass
dominated ecosystems, which represent about 30% of primary production of all terrestrial
vegetation and store 10-30% of all soil organic carbon (SOC). However, improved
predictions of the impacts of future climate-driven changes on the tropical soil organic
matter (SOM) pool requires a more detailed and predictive understanding of the
interactions between vegetation, climate, edaphic and disturbance effects than is currently
available. Field studies using the stable carbon isotopic composition of SOM can help
assessing the influence of C3 and C4 vegetation on SOM dynamics, enabling a test to
determine whether there are differential patterns in their mineralisation potential as
previously reported in laboratory-based studies. To this end, variations in the carbon
isotopic composition of 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. Moreover, results
were also interpreted in light of the relative change in C/N ratios observed between
contrasting SOM fractions in order to assess potential differences in SOM dynamics
between Grass- and Tree-dominated sampling locations. Differential patterns in SOM
dynamics in C3/C4 mixed ecosystems occurred at various spatial scales. At the site
scale, differing degrees of SOM decomposition were observed between locations
dominated locally by either tree or grass vegetation as indicated by the relative change in
C/N ratios between contrasting SOM fractions. While at the transect scale, the
non-linear nature of the relationship between δ13C and SOC content observed across
the gradient strongly suggests that in addition to the inherent differences in the
input rates and turnover times of tree and grass-derived carbon, the broad range of
edaphic characteristics exert a strong influence on both the physical protection and
chemical stabilization of SOM. Finally, we show 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. |
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