David Sebag

David Sebag
IFP Energies nouvelles · Geosciences Division

Ph.D (Geosciences)

About

190
Publications
58,545
Reads
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2,335
Citations
Citations since 2016
82 Research Items
1527 Citations
2016201720182019202020212022050100150200250
2016201720182019202020212022050100150200250
2016201720182019202020212022050100150200250
2016201720182019202020212022050100150200250
Introduction
Geoscientist with broad experience both in geosciences (sedimentology, surficial processes, geochemistry) and environmental sciences (pedology, ecology, climatology). I have undertaken research about sedimentary dynamics of tropical lakes and organic matter in the terrestrial environments. I work about respective impact of climate changes and human activities on past and current ecosystems in tropical and equatorial Africa (Niger, Chad, Cameroun, Gabon).
Additional affiliations
March 2014 - December 2015
Institute of Research for Development
Position
  • Researcher
March 2013 - February 2014
Institute of Research for Development
Position
  • Researcher
August 2012 - December 2016
Institute of Research for Development
Position
  • LABORATOIRE MIXTE INTERNATIONAL - PICASS’EAU
Description
  • http://www.davidsebag.fr/Africaproject/Yaounde/Yaounde.html
Education
August 1999 - October 2002
Université de Rouen
Field of study
  • Surficial Geosciences
January 1999 - August 1999
Université de Rouen
Field of study
  • Geoarcheology
September 1997 - June 1998
University of Burgundy
Field of study
  • Sedimentology

Publications

Publications (190)
Article
Full-text available
Organic matter (OM) is a key component of soils but information on its chemistry and behavior in soils is still incomplete. Numerous methods are commonly used to characterize and monitor OM dynamics, but only a few include the qualities required to become routine techniques i.e. simple, rapid, accurate and at low cost. Rock–Eval pyrolysis (RE pyrol...
Article
Full-text available
a b s t r a c t Mountain soils store huge amounts of carbon which may be highly vulnerable to the strong land use and climate changes that mountain areas currently experience worldwide. Here, we tested the Rock–Eval (RE) pyrolysis as a proxy technique to (i) quantify soil organic carbon (SOC) stocks, (ii) bring insights into SOC bulk chemistry and...
Article
Application of Rock-Eval pyrolysis to soil organic matter (SOM) quantitation and characterization has been explored by the study of about 100 soil samples taken from a variety of soil profiles from different ecosystems at different latitudes. A straightforward illustration of these possibilities can be obtained from a Hydrogen Index (HI in mg hydro...
Article
Rock-Eval pyrolysis was designed for petroleum exploration to determine the type and quality of organic matter in rock samples. Nevertheless, this technique can be used for bulk characterization of the immature organic matter in soil samples and recent sediments. We studied 76 samples from seven soil classes and showed that their pyrograms can be d...
Article
Full-text available
The forested swamps of the central Congo Basin store approximately 30 billion metric tonnes of carbon in peat1,2. Little is known about the vulnerability of these carbon stocks. Here we investigate this vulnerability using peat cores from a large interfluvial basin in the Republic of the Congo and palaeoenvironmental methods. We find that peat accu...
Preprint
Full-text available
Microbes are responsible for cycling carbon (C) through soils, and the predictions of how soil C stocks change with warming are highly sensitive to the assumptions made about the mechanisms controlling the microbial physiology response to climate warming. Two mechanisms, microbial thermal-acclimation and changes in the quantity and quality of subst...
Poster
Full-text available
WCSS22 Abstract of poster P-902 Does a mixture of compost and minerals become soil after five years? The answer from organic matter. We study the evolution of certain soils under spontaneous conditions on experimental plot in situ with living organisms (insects, earthworms, plants…) in order to understand the development of their hydro-structural...
Article
A core from a peat bog in the “Niayes” region, northwest of Senegal, provides a valuable insight into the evolution of the landscape and fire regime related to the West African Monsoon rainfall and to human impact over the Holocene. The high-resolution multiproxy approach based on stable carbon isotopic composition (δ¹³C), Rock-Eval® thermal analys...
Poster
Full-text available
Findings ➢ The Rock-Eval® thermal method proved to be accurate and sensitive enough to discriminate the effects of amendments and cultivation on SOM properties and organic C storage, despite small variations after 7-week cultivation ➢ Biochar and Biochar+NPK probably favoured organic C storage in soil during cultivation, though the OM stability r...
Poster
Full-text available
➢ The Rock-Eval® thermal method is increasingly used in soil science to quantify Soil Organic Carbon (SOC) and Soil Inorganic Carbon (SIC) contents, due to its reliability, speed and ease of execution ➢The SOTHIS correction method provides SOC and SIC with improved accuracy, based on a conventional Rock-Eval® thermal analysis ➢ Applied to differe...
Article
Full-text available
Sedimentary organic matter (OM) analyses along a 130 km long transect of the Mkhuze River from the Lebombo Mountains to its outlet into Lake St Lucia, Africa's most extensive estuarine system, revealed the present active trapping function of a terminal freshwater wetland. Combining bulk OM analyses, such as Rock-Eval®, and source-specific biomarker...
Article
Full-text available
The Black Death (1347–1352 ce ) is the most renowned pandemic in human history, believed by many to have killed half of Europe’s population. However, despite advances in ancient DNA research that conclusively identified the pandemic’s causative agent (bacterium Yersinia pestis ), our knowledge of the Black Death remains limited, based primarily on...
Article
Full-text available
Tropical rivers emit large amounts of carbon dioxide (CO2) to the atmosphere, in particular due to large wetland-to-river carbon (C) inputs. Yet, tropical African rivers remain largely understudied, and little is known about the partitioning of C sources between wetland and well-drained ecosystems to rivers. In a first-order sub-catchment (0.6 km2)...
Article
Full-text available
Rubber tree plantations (Hevea brasiliensis) cover large areas in the tropics. In historical producing regions like South Thailand, rubber has been planted by smallholders for three successive rotations lasting a total of 75 years. Despite possible consequences on topsoil, the long-term impacts of repeated rubber plantations on soil quality remain...
Article
Full-text available
The largest terrestrial carbon sink on earth is soil carbon stocks. As the climate changes, the rate at which the Earth’s climate warms depends in part on the persistence of soil organic carbon. Microbial turnover forms the backbone of soil organic matter (SOM) formation and it has been recently proposed that SOM molecular complexity is a key drive...
Article
Full-text available
Palaeocological studies show that major vegetation and environmental changes occurred in Central Africa from the mid-Holocene (e.g. Maley & Brenac 1998). Several suggest a human origin and assume that large population migration, technical innovations (e.g. iron-smelting technology) and/or change in agricultural practice, leading to deforestation an...
Article
Full-text available
Palaeocological studies show that major vegetation and environmental changes occurred in Central Africa from the mid-Holocene (e.g. Maley & Brenac 1998). Several suggest a human origin and assume that large population migration, technical innovations (e.g. iron-smelting technology) and/or change in agricultural practice, leading to deforestation an...
Article
Palaeocological studies show that major vegetation and environmental changes occurred inCentral Africa from the mid-Holocene (e.g.Maley & Brenac 1998). Several suggest a human origin and assume that large population migration, technical innovations (e.g. iron-smelting technology) and/or change in agricultural practice, leading to deforestation and...
Preprint
Full-text available
Sedimentary organic matter (OM) analyses along a 130 km-long transect of the Mkhuze River from the Lebombo Mountains to its outlet into Lake St. Lucia, Africa’s most extensive estuarine system, revealed the present active trapping function of a terminal freshwater wetland. A combination of organic bulk parameters, thermal analyses, and determinatio...
Article
Both biotic and abiotic components, characterizing the mountain treeline ecotone, respond differently to climate variations. This study aims at reconstructing climate-driven changes by analyzing soil evolution in the late Holocene and by assessing the climatic trends for the last centuries and years in a key high-altitude climatic treeline (2515 m...
Article
Soil organic matter (OM) is a complex heterogeneous mixture: resulting from decomposition and organo-mineral interactions, it challenges characterization in terms of composition and biogeochemical stability. From this perspective, the Rock-Eval® method is a rapid and efficient thermal analysis, which combines quantitative and qualitative informatio...
Preprint
Full-text available
The Black Death is the most reknown pandemic in human history, believed by many to have killed half of Europe's population. However, despite the advances in ancient DNA research that allowed for the successful identification of the pandemic's causative agent (bacterium Yersinia pestis), our knowledge of the Black Death is still limited, based prima...
Presentation
Full-text available
vPICO presented at session SSS 9.7 "Impact of conventional agriculture and organic farming on soil functions"
Preprint
Full-text available
The largest terrestrial carbon sink on earth is soil carbon stocks. As the climate changes, the rate at which the Earth’s climate warms depends in part on the persistence of soil organic carbon. Microbial turnover forms the backbone of soil organic matter (SOM) formation and it has been recently proposed that SOM molecular complexity is a key drive...
Preprint
Full-text available
We characterized the spatio-temporal dynamics of carbon (C) in rivers of the tropical Nyong catchment (South Cameroon). In 2016, we measured fortnightly at 6 locations along an upstream-downstream gradient from groundwater to the main stream of order 6, total alkalinity, dissolved inorganic C (DIC) used together with pH to compute pCO2, dissolved a...
Article
Holocene paleoecological studies in tropical Africa are rare because most lakes either dried out at the termination of the African Humid Period or have since filled up. However, tropical sedge marshes can be an alternative to perform long-term ecological studies. The Lopé National Park (LNP) in Gabon is a mosaic of forest and savanna enclosed in th...
Conference Paper
Full-text available
Soil carbon (C), now more than ever, attracts the interest of the scientific community for its importance in combating climate change and achieving food security. As a result, its key role in agricultural soil fertility and in anthropogenic greenhouse gas emissions mitigation is high on international agendas. A key issue regarding the linkage betwe...
Article
Full-text available
Calcium is a key element of the Earth system and closely coupled to the carbon cycle. Weathering of silicate releases Ca, which is exported and sequestered in oceans. However, pedogenic calcium carbonate constitutes a second Ca‐trapping pathway that has received less attention. Large accumulations of pedogenic calcium carbonate nodules, associated...
Article
L'introduction de l'agriculture en Europe, souvent appelée "Révolution néolithique", suggère une " grande transition" analogue à celle que nous expérimentons aujourd'hui : un changement complexe, profond et rapide des sociétés et de leur environnement. Toutefois, le scénario de néolithisation de l'Europe, souvent simplifié, est loin d'être générali...
Article
Complex sequences of paleosols are often formed by the interaction between pedogenesis and geomorphological evolution. Their study, particularly in mountain areas, is useful to reconstruct past environmental conditions as well as climate shifts, and to gather information on the morphodynamical processes affecting the landscape through time. Since t...
Article
The assessment of the impacts of land-use and management on soil organic carbon (SOC) dynamics is a major environmental concern, as the soil carbon cycle underpins key ecosystem services. However, assessments based on short-term SOC dynamics face methodological and experimental difficulties. Hurisso et al. (2016) proposed a method to assess SOC dyn...
Article
Full-text available
Coronavirus disease (COVID-19), caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), is rapidly spreading across the globe. The clinical spectrum of SARS-CoV-2 pneumonia requires early detection and monitoring, within a clinical environment for critical cases and remotely for mild cases, with a large spectrum of symptoms. The...
Conference Paper
Full-text available
Soil organic carbon (SOC) is a key element in the functioning of agrosystems. It ensures soil quality and productivity of cultivated systems in the Sahelian region. This study uses Rock-Eval pyrolysis to examine how cultural practices impact SOC quantity and quality of cultivated sandy soils in the Senegal groundnut basin. Such thermal analysis met...
Article
Soil structure formation in alluvial soils is a fundamental process in near-natural floodplains. A stable soil structure is essential for many ecosystem services and helps to prevent river bank erosion. Plants and earthworms are successful soil engineering organisms that improve the soil structural stability through the incorporation of mineral and...
Article
Full-text available
Inter-tropical regions are nowadays faced to major land-use changes in data-sparse context leading to difficulties to assess hydrological signatures and their evolution. This work is part of the theme Panta Rhei of the IAHS, and aims to develop a combined approach of data acquisition and a new semi-distributed model taking into account land-use cha...
Article
Full-text available
Qualitative and quantitative changes of organic and carbonate carbon in sedimentary records are frequently used to reconstruct past environments, paleoproductivity and sediment provenance. Amongst the most commonly used proxies are Total organic carbon (TOC), Mineral carbon (MinC), as well as Hydrogen (HI) and Oxygen Indices (OI) of organic matter...
Article
Full-text available
Biodiversity research in tropical ecosystems - popularized as the most biodiverse habitats on Earth - often neglects invertebrates, yet representing the bulk of local species richness. Insect communities in particular remain strongly impeded by both Linnaean and Wallacean shortfalls, and identifying species often remains a formidable challenge inhi...
Article
Sub-Saharan urban centers have to tackle high population growth, lack of sanitation infrastructures and the need for good quality water resources. To characterize the impacts of anthropization on the water resources of the capital of Cameroon (Yaoundé), a multi-disciplinary approach was used in ten sub-watersheds (peri-urban and urban) of the Méfou...
Article
Full-text available
Our understanding of mechanisms governing soil organic matter (OM) stability is evolving. It is gradually becoming accepted that soil OM stability is not primarily regulated by the molecular structure of plant inputs, but instead by the biotic and abiotic properties of the edaphic environment. Moreover, several experimental studies conducted in art...
Article
Climate and environmental changes since the Last Glacial Maximum in the tropical zone of West Africa are usually inferred from marine and continental records. In this study, the potential of carbonate pedo-sedimentary geosystems, i.e. Vertisol relics, to record paleoenvironmental changes in the southwestern part of Chad Basin are investigated. A mu...
Poster
Full-text available
The capacity of soils to mitigate climate change through carbon sequestration depends on the quantitative but also the qualitative changes in soil organic carbon (SOC). In particular, the stability of SOC has to be considered to evaluate the long-term fate of the soil carbon stocks. The aim of this study was to assess the accurateness of thermal an...
Article
Full-text available
Urban agriculture is crucial to local populations, but the risk of it contaminating water has rarely been documented. The aim of this study was to assess pesticide contamination of surface waters from the Méfou watershed (Yaoundé, Cameroon) by 32 selected herbicides, fungicides, and insecticides (mainly polar) according to their local application,...
Article
Clist et al. (1) challenge our conclusions (2), criticizing our archaeological synthesis to maintain that the late Holocene rainforest crisis (LHRC) in Western Central Africa (WCA) was not triggered by human activity. Clist et al. (1) claim that the archaeological 14C dates we used were not critically evaluated, as we were more concerned with the q...
Article
Originally developed for use in the petroleum industry, Rock-Eval pyrolysis is a technique commonly applied to lake sediments to infer paleoenvironmental reconstructions. The standard Rock-Eval parameters provide information on the amount of total organic and inorganic carbon (TOC and MinC, respectively), and are usually interpreted as proxies for...
Article
Full-text available
Background and Aims The oxalate-carbonate pathway (OCP) has been observed in acidic tropical soils with low alkaline cation content where compartments are transient and fed by the rapid turnover of organic matter. By acting on edaphic parameters, the OCP may influence soil nutrient distribution. This study aims at assessing the influence of the OCP...
Article
Full-text available
The rapid expansion of perennial crops is a major threat to biodiversity in Southeast Asia. The biodiversity losses related to the conversion of forest lands to oil palm or rubber plantations (RP) are well documented by recent studies. However, the impact of the conversion from intensively managed annual crops to perennial crops on soil biodiversit...