Vincent Chaplot

• PhD, HDR
• Researcher at Institute of Research for Development

The identification of runoff source areas is essential for Integrated Water and Resources Management (IWRM). Although direct methods for the determination of steady-state water infiltration in soils (Inf) do exist, these are tedious and time-consuming. Geophysical techniques offer an alternative, however, geophysical data are often misinterpreted,...

Despite the increasing interest in the role of soil erosion on the global carbon cycle, few studies were carried out to evaluate the fate of eroded organic carbon (OC) at the landscape level. Although eroded C may consti-tute an atmospheric C source upon mineralization or a C sink if entrapped, it is largely unknown how land-scape position and mole...

Gully erosion is one of the main causes of soil loss in drylands. Understanding the dominant mechanisms of erosion is important to achieve effective erosion control, thus in this study our main objective was to quantify the mechanisms involved in gully bank retreat as a result of three processes, falling of entire soil aggregates, transport of soil...

Although no-till (NT) is now practiced in many countries of the world, for most smallholders, the crop residues are of such a value that they cannot be left on the soil surfaces to promote soil protection, thus potentially limiting NT benefits and adoption. In this study our main objective was to evaluate runoff, soil, and soil organic carbon (SOC)...

In most regions of the world overgrazing plays a major role in land degradation and thus creates a major threat to natural ecosystems. Several feedbacks exist between overgrazing, vegetation, soil infiltration by water and soil erosion that need to be better understood. In this study of a sub-humid overgrazed rangeland in South Africa, the main obj...

Digital Elevation Models (DEMs) have been successfully used in a large range of environmental issues. Several methods such as digital contour interpolation and remote sensing have allowed the generation of DEMs, some of which are now freely available for almost the entire globe. The Soil and Water Assessment Tool (SWAT) is a widely used semi-distri...

Conventional soil science methods for the estimation of the spatial variations of soil properties within landscapes are destructive, time consuming, and do not allow the estimation of the short range variability. Recent advances in geomatic global positioning systems and sensors offer new possibilities for the mapping of spatially varying soil patt...

The fate of black carbon deposited on the soil surface after burning of harvesting residues is poorly understood. In this study we quantified horizontal as well as vertical transport of total pyrogenic carbon and its chemically most stable part (OREC) during a rainfall experiment after an experimental burn. The aim of the study was to assess the im...

Surface soils, which contain the largest pool of terrestrial organic carbon (C), may be able to sequester atmospheric C and thus mitigate climate change. However, this remains controversial, largely due to insufficient data and knowledge gaps in respect of organic C contents and stocks in soils and the main factors of their control. Up to now and d...

The main objectives of this study were to evaluate soil organic C (SOC) variability in a representative hillslope of Laos and to quantify the impact of some environmental factors. We collected 2348 soil samples from 581 georeferenced soil pits within a hillslope of northern Laos under traditional shifting cultivation at 0- to 0.05-m depth and then...

Our objective was to evaluate the fate of eroded carbon at landscape level in a steep slope area of the Mekong basin submitted to traditional slash-and-burn (SAB) agriculture. We monitored carbon erosion at different spatial scales ranging from 1m² (micro-plot level) installed within a hillslope to 1×107 m² (watershed). Samples were taken throughou...

The fate of black carbon deposited on the soil surface after burning of harvesting residues is poorly understood. In this study we quantified horizontal as well as vertical transport of total pyrogenic carbon and its chemically most stable part (OREC) during a rainfall experiment after an experimental burn. The aim of the study was to assess the im...

Rapid changes in upland farming systems in Southeast Asia generated predominantly by increased population pressure and ‘market forces’ have resulted in widespread land degradation that has been well documented at the plot scale. Yet, the links between agricultural activities in the uplands and downstream off-site effects remain largely unknown beca...

Black carbon (BC) produced during slash and burn agriculture on tropical soils may enhance the soils organic matter content and hence their biological properties. However, once deposited on the soil surface, BC may be subject to erosion and/or microbial decomposition and thus not be preserved on site. Up to now, few studies have been carried out to...

in : Ribolzi O. (Ed.), Pierret A. (Ed.), Gebbie L. (Ed.), Sengtaheuanghoung O. (Ed.), Chanphengxay M. (Préf.) Management of soil erosion and water resources in the uplands of Lao P.D.R.

Soil organic matter (SOM) stabilisation on tropical sloping land can be influenced by slash burning and erosion processes. However, information on the behaviour of potentially stable components of organic matter on burned sites is scarce. This study is focused on organic matter soluble after demineralisation of the samples with hydrofluoric acid (H...

Brazil is the world's largest sugarcane producer, so changes in sugarcane management in Brazil can affect the environment to a great extent. During almost one century, studies were carried out in cropping systems involving pre-harvest burning of aerial sugarcane residues. Nowadays the green trash management of sugarcane residues has become a common...

Brazil is the world's largest sugarcane producer, so changes in sugarcane management in Brazil can affect the environment to a great extent. During almost one century, studies were carried out in cropping systems involving pre-harvest burning of aerial sugarcane residues. Nowadays the green trash management of sugarcane residues has become a common...

Land use policies together with growing market demand have resulted in rapid land use changes in the uplands of the Lao PDR over the past few years. These changes have led to questions concerning the link between agricultural activities and off-site impacts. To tackle this issue the Management of Soil Erosion Consortium has equipped a catchment in...

The quantification of the diverse responses of soils and terrestrial fresh water to elevated levels of greenhouse gases and to climate change is crucial for the proper management of natural ecosystems in the future. Despite previous experiments and simulations, there is still a need for the evaluation of the impact of these global changes at the wa...

In this study our main objective was to quantify water interrill erosion in the sloping lands of Southeast Asia, one of the most bio-geochemically active regions of the world. Investigations were performed on a typical hillslope of Northern Laos subjected to slash and burn agriculture practiced as shifting cultivation. Situations with different per...

One of the most important scientific challenges of digital soil mapping is to develop generic models that may allow the soils to be predicted over large areas. Our objective here is to quantify the relationships between the soils and their “environment” to further our understanding of the rules of soil distribution. The study was conducted in the A...

One of the most important scientific challenges of digital elevation modeling is the development of numerical representations of large areas with a high resolution. Although there have been many studies on the accuracy of interpolation techniques for the generation of digital elevation models (DEMs) in relation to landform types and data quantity o...

In this study we investigated the quantitative and qualitative aspects of soil organic matter (SOM) losses caused by water erosion within a small catchment in Northern Laos, under steep slopes and slash and burn agriculture. The soils in the region have a high contribution of black carbon to soil organic matter and high erosion rates. The aim of th...

Tropical soils are generally depleted in organic carbon (OC) due to environmental conditions favouring decomposition and mineralisation of soil organic matter (SOM). In Northern Laos, sloping soils are subjected to slash and burn agriculture, which leads to production of black carbon (BC), a stable SOM fraction. BC may directly influence the quanti...

In a given watershed, the accuracy of models in predicting the hydrologic and erosion behavior depends, to a large extent, on the quality of the knowledge in respect of the spatial rainfall. The hydrologic and erosion aspects of rainfall are often discussed without due regard to any resulting improvement in watershed modeling. Thus, there is a real...

Linear erosion (LE), including rilling and gullying, has been identified as the major problem for sustainable agriculture in steepland areas. It causes severe environmental, economic, and social impacts. This issue is even more crucial in those areas undergoing rapid changes in land use, as for example northern Laos, and may dramatically affect soi...

The accuracy of agricultural nonpoint source pollution models depends to a great extent on how well model input spatial parameters describe the relevant characteristics of the watershed. It is assumed that reducing the precision of spatial input parameters affects the simulation results of runoff and sediment yield from the entire watershed. Howeve...

Linear erosion (LE) induced either by piping or overland flow is one of the most active factors in the evolution of soils. During single storm events LE may remove enormous amounts of soil material from the uplands to the bottomlands and has thus become a broad challenge for food supply, food security, and human health. Recent and rapid changes in...

Microaggregates that characterize ferralic soils have been hypothesized to have physical, geochemical and/or biological origins. Despite of many studies, the hierarchy between these processes that form microaggregates has seldom been reported. The objective of this work was to study the genesis of microaggregates in a sequence of Ferralic Nitisols...

[ 1] This study quantified the soil and carbon fluxes caused by water erosion within the sloping uplands of the Mekong River basin, a river system carrying one of the greatest worldwide amounts of sediment to the ocean. Losses of sediment and soil organic carbon (SOC) ( including black carbon, BC) were evaluated within an agricultural catchment of...

So far, soil-landscape models have been based on soil surface topographic information only. However, hillslope hydrology that affects soil distribution is also controlled by sub-surface flow pathways that may not entirely be explained by surface terrain features. This paper compares the accuracy of a model for predicting the spatial variations of t...

Our main objective in the present study was to assess the spatial variation of chemical and physical soil properties and then use this information to select an appropriate area to install a pasture rehabilitation experiment in the Amazon region, Brazil. A regular 25 m grid was used for collecting a total of 2955 soil samples (from 985 georeferenced...

Changes in land-use or management practices may affect water outflow, sediment, nutrients and pesticides loads. Thus, there is an increasing demand for quantitative information at the watershed scale that would help decision makers or planners to take appropriate decisions. This paper evaluates by a modeling approach the impact of farming practices...

Geophysical methods have already shown their interest for the continuous characterisation of soils over landscapes, rapidly and, non-intrusively. But in bottomland areas, difficulties are encountered in relating geophysical properties to soil spatial distribution due to large variations in the depth, texture and/or water content of soils. Indeed, r...

Geophysical methods have already shown their interest for the continuous characterisation of soils over landscapes, rapidly and, non-intrusively. But in bottomland areas, difficulties are encountered in relating geophysical properties to soil spatial distribution due to large variations in the depth, texture and/or water content of soils. Indeed, r...

A better knowledge of the spatial distribution of soils over landscapes is one of the key issue for environmental modelling. Although digital elevation models (DEMs) and land use maps are fairly easy to generate, other important pieces of information such as the spatial distribution of soils or soil properties are not so easy to obtain. Quantitativ...

Soil spatial distribution, i.e. the spatial distribution of soils within landscapes, is difficult to predict because numerous processes operate simultaneously, but variably, over time. Quantifications of large areas with an acceptable degree of precision and low in cost require the development of specific methods making the best possible use of exi...

The estimation of the spatial distribution of soil wetness within a catchment is one of the most important issues in hydrological and erosion modelling. So far, such models have been based on soil surface topographic information only. However, soil hydrology is also controlled by subsurface flow pathways that may not be explained only by surface te...

Quantitative soil-landscape models, based on topographic attributes, make possible the characterization of large areas because of the widespread availability of digital elevation models (DEMs). However, these soil-landscapes models, which are usually generated and validated on the same detailed, single research site, such as a hillslope or an eleme...

In agricultural landscapes, factors affecting V under steady-state conditions of infiltration are well docu- Various interactions, particularly those existing between the rain- by all three factors: rainfall intensity (r 0.48; P 0.0001), slope gradient (r 0.51; P 0.0001) and slope length (r 0.29; P 0.02); "For a constant runoff rate rain impacted f...

Attempts to map vegetation types, especially pasture, from satellite sensor data in tropical and sub-tropical regions very often have limited success. This study analyses the accuracy of two classifications of Landsat Thematic Mapper (TM), with the aim of distinguishing the pastures from other vegetation classes in a meso-scale basin (12 400 km 2,...

40 ref. *INRA UMR Sol Agronomie Spatialisation Rennes (FRA) Diffusion du document : INRA UMR Sol Agronomie Spatialisation Rennes (FRA)

Pedological soil surveys usually based on auger sampling encounter methodological and economic difficulties. Electrical resistivity (ER) techniques could be used as a simple and practical method to determine their spatial variability. However, attempts to map soils using ER techniques have very often limited success, especially in bottomland areas,...

Because soils are both a source and a sink for atmospheric CO2, there is an increasing need to characterize the spatial distribution of soil C pools. Large amounts of organic carbon (OC) accumulate in hydric bottom-lands soils. In the Armorican Massif (Western France) where these soils represent 20% of the total surface area, the spatial characteri...

Soil-landscape models have prediction errors that can be reduced by using auxiliary soil data. However, standard soil surveys using auger hole and laboratory analysis encounter both methodological and economical constraints because of, for example, the short-range variability of soils and the expensive field work. In the present study, the objectiv...

In regions with intensive agriculture and shallow hydrological systems, headstreams are often polluted with nitrate even at the springs. In North-West France, nitrate concentration was seen to decrease downstream during baseflow conditions when the stream flows on granite, but this does not occur on schist. In order to explain this difference in be...

This study analyses the sensitivity of soil hydromorphy prediction methods with regard to the resolution of topographical information and additional soil data. Seven Digital Elevation Models (DEM) were computed and compared to topographic measurements, with different resolutions (10, 20, 30 and 50 m) and construction mode (inputting actual stream l...

Soil maps analysis to identify the role of the tectonic regime on saprolite permeability regional distribution. For applied geology, e.g., geotechnics or hydrogeology, it is of prime interest to know the spatial distribution of the saprolite permeability. This study focuses on the role of the tectonic regime on saprolite permeability regional distr...

Despite numerous studies, the effect of slope on interrill erosion is not clearly established. Several interactions exist between erosion parameters that are not taken into account under experimental laboratory measurements and results need to be validated in the field. The influence of slope steepness (2 to 8 per cent) on soil loss for a crusted i...

Knowledge of the bottomland hydric functioning in humid zones is important in order to estimate denitrification that takes place in anaerobic conditions. The objective of this study was to point out the temporal dynamics of soil cover redox conditions for different geological substrates and to compare these dynamics to soil morphological features....

The study of pedological maps from the Armorican Massif evidenced the effect of recent tectonics (500 000–700 000 years BP) on the regional hydromorphic soil distribution. Blocs in relative uplift were characterized by a low proportion of hydromorphic soils, whereas a higher proportion marked blocs in relative downlift. Such clear differences can b...

Water erosion is one of the most active processes in soil genesis and dynamics. It is also at the origin of significant environmental problems. Soil surface state is one of the most important factors for erosion risk assessment. However, it is not easy to determine the effect of this factor at a large scale. A field experiment was held in Pays de C...

Les mesures de pertes en eau et en terre, réalisées dans un contexte de région limoneuse intensivement cultivée du Nord-Ouest de la France à l'échelle de 1 m2, sont présentées et commentées. L'érosion hydrique est l'un des processus majeurs dans la redistribution des particules solides du sol au sein des paysages. Aussi, afin d'estimer dans un prem...