The influence of woody thickening on SOM dynamics along a precipitation gradient in West Africa

G. Saiz, M. Bird, C. Wurster, P. Ascough, E.M. Veenendaal, K. Butterbach-Bahl

Research output: Contribution to conferenceAbstract


We made use of the carbon isotopic composition of soil organic matter (SOM) in bulk and fractionated samples to assess the influence of C3/C4 vegetation on SOM dynamics in semi-natural tropical ecosystems sampled along a precipitation gradient in West Africa. The non-linear nature of the relationship between 13C and SOC content observed across the latitudinal 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 may have a major effect in both the physical protection of particulate organic carbon and the chemical stabilization of 13C enriched microbial metabolites. The stable carbon isotopic composition of SOM with depth indicated that there was a larger proliferation in woody vegetation with increasing precipitation, with such trend being also heavily dependent on the characteristics of the soils. An unbiased assessment of the potential impact of tropical vegetation thickening on SOM dynamics is characteristically difficult given the confounding effects posed by the interaction of varying climatic and edaphic factors. Therefore, in order to minimize the impact of those factors, we selected two neighboring transitional ecosystems (a closed savanna woodland and a semideciduous dry forest) occurring in soils of comparable characteristics. Both sites showed varying degrees of 13C enrichment with depth in bulk and fractionated SOM. Moreover, radiocarbon analyses of sand-size aggregates (>53 m HF) yielded relatively short MRT, which shows highly dynamic SOM processes even in fairly deep locations. Interestingly, the most stable SOM fraction associated to silt and clay (
Original languageEnglish
Publication statusPublished - 2014
EventEGU General Assembly 2014 - Vienna
Duration: 27 Apr 20142 May 2014


ConferenceEGU General Assembly 2014

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