Continental-scale controls on soil organic carbon across sub-Saharan Africa

A - Papers appearing in refereed journals

Von Fromm, S. F., Hoyt, A. M, Lange, M., Acquah, G., Aynekulu, E., Berhe, A. A, Haefele, S. M., McGrath, S. P., Shepherd, K. D., Sila, A. M., Six, J., Towett, E. K, Trumbore, S. E., Vagen, T.-G, Weullow, E., Winowiecki, L. A. and Doetterl, S. 2021. Continental-scale controls on soil organic carbon across sub-Saharan Africa. Soil. 7, pp. 305-332. https://doi.org/10.5194/soil-7-305-2021

AuthorsVon Fromm, S. F., Hoyt, A. M, Lange, M., Acquah, G., Aynekulu, E., Berhe, A. A, Haefele, S. M., McGrath, S. P., Shepherd, K. D., Sila, A. M., Six, J., Towett, E. K, Trumbore, S. E., Vagen, T.-G, Weullow, E., Winowiecki, L. A. and Doetterl, S.
Abstract

Soil organic carbon (SOC) stabilization and destabilization has been studied intensively. Yet, the factors which control SOC content across scales remain unclear. Earlier studies demonstrated that soil texture and geochemistry strongly affect SOC content. However, those findings primarily rely on data from temperate regions where soil mineralogy, weathering status and climatic conditions generally differ from tropical and subtropical regions. We investigated soil properties and climate variables influencing SOC concentrations across sub-Saharan Africa. A total of 1601 samples were analyzed, collected from two depths (0–20 and 20–50 cm) from 17 countries as part of the Africa Soil Information Service project (AfSIS). The data set spans arid to humid climates and includes soils with a wide range of pH values, weathering status, soil texture, exchangeable cations, extractable metals and land cover types. The most important SOC predictors were identified by linear mixed-effects models, regression trees and random forest models. Our results indicate that geochemical properties, mainly oxalate-extractable metals (Al and Fe) and exchangeable Ca, are equally important compared to climatic variables (mean annual temperature and aridity index). Together, they explain approximately two-thirds of SOC variation across sub-Saharan Africa. Oxalate-extractable metals were most important in wet regions with acidic and highly weathered soils, whereas exchangeable Ca was more important in alkaline and less weathered soils in drier regions. In contrast, land cover and soil texture were not significant SOC predictors on this large scale. Our findings indicate that key factors controlling SOC across sub-Saharan Africa are broadly similar to those in temperate regions, despite differences in soil development history.

Year of Publication2021
JournalSoil
Journal citation7, pp. 305-332
Digital Object Identifier (DOI)https://doi.org/10.5194/soil-7-305-2021
Open accessPublished as non-open access
FunderBiotechnology and Biological Sciences Research Council
Funder project or code BBS/OS/GC/000014B
S2N - Soil to Nutrition - Work package 1 (WP1) - Optimising nutrient flows and pools in the soil-plant-biota system
Output statusPublished
Publication dates
Online29 Jun 2021
Publication process dates
Accepted12 May 2021
PublisherEuropean Geosciences Union (EGU)
ISSN2199-3971

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