Variation in soil carbon stocks and their determinants across a precipitation gradient in West Africa

Saiz, Gustavo, Bird, Michael I., Domingues, Tomas, Schrodt, Franziska, Schwarz, Michael, Feldpausch, Ted R., Veenendaal, Elmar, Djagbletey, Gloria, Hien, Fidele, Compaore, Halidou, Diallo, Adama, and Lloyd, Jon (2012) Variation in soil carbon stocks and their determinants across a precipitation gradient in West Africa. Global Change Biology, 18 (5). pp. 1670-1683.

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Abstract

We examine the influence of climate, soil properties and vegetation characteristics on soil organic carbon (SOC) along a transect of West African ecosystems sampled across a precipitation gradient on contrasting soil types stretching from Ghana (15°N) to Mali (7°N). Our findings derive from a total of 1108 soil cores sampled over 14 permanent plots. The observed pattern in SOC stocks reflects the very different climatic conditions and contrasting soil properties existing along the latitudinal transect. The combined effects of these factors strongly influence vegetation structure. SOC stocks in the first 2 m of soil ranged from 20 Mg C ha−1 for a Sahelian savanna in Mali to over 120 Mg C ha−1 for a transitional forest in Ghana. The degree of interdependence between soil bulk density (SBD) and soil properties is highlighted by the strong negative relationships observed between SBD and SOC (r2 > 0.84). A simple predictive function capable of encompassing the effect of climate, soil properties and vegetation type on SOC stocks showed that available water and sand content taken together could explain 0.84 and 0.86 of the total variability in SOC stocks observed to 0.3 and 1.0 m depth respectively. Used in combination with a suitable climatic parameter, sand content is a good predictor of SOC stored in highly weathered dry tropical ecosystems with arguably less confounding effects than provided by clay content. There was an increased contribution of resistant SOC to the total SOC pool for lower rainfall soils, this likely being the result of more frequent fire events in the grassier savannas of the more arid regions. This work provides new insights into the mechanisms determining the distribution of carbon storage in tropical soils and should contribute significantly to the development of robust predictive models of biogeochemical cycling and vegetation dynamics in tropical regions.

Item ID: 22159
Item Type: Article (Refereed Research - C1)
Keywords: precipitation gradient, resistant organic carbon, soil bulk density, soil carbon stocks, soil organic carbon, tropical ecosystems, West Africa
ISSN: 1365-2486
Date Deposited: 28 Jun 2012 16:22
FoR Codes: 05 ENVIRONMENTAL SCIENCES > 0503 Soil Sciences > 050301 Carbon Sequestration Science @ 70%
04 EARTH SCIENCES > 0406 Physical Geography and Environmental Geoscience > 040601 Geomorphology and Regolith and Landscape Evolution @ 30%
SEO Codes: 96 ENVIRONMENT > 9614 Soils > 961403 Forest and Woodlands Soils @ 50%
96 ENVIRONMENT > 9614 Soils > 961406 Sparseland, Permanent Grassland and Arid Zone Soils @ 50%
Citation Count from Web of Science Web of Science 2
Downloads: Total: 3
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