Soil Mapping and Soil Monitoring:
State of Progress and Use in France
Le Bas C.1
1 INRA, Unités Infosol et Science du Sol, Avenue de la Pomme de Pin, BP 20619 Ardon,
45166 OLIVET CEDEX, France
2INRA, Direction Scientifique ECONAT, Domaine St Paul - Site Agroparc,
84914 AVIGNON CEDEX 9, France
The Soil Survey Staff of France was founded in 1968 within INRA (National Institute of Agronomic Research) to ensure the co-ordination of the national soil mapping and monitoring programmes in France in a mainly agricultural context. During the last ten years, environmental problems have arisen and consequently led to an increase in the need for soil information. However, at the same time, the resources allocated to these programmes have been significantly reduced (King
et al., 1999).
Considering this new context and the need for a good knowledge about the spatial distribution of soils, and the evolution of their properties, a new structure was created in 2001 to re-organise soil mapping and soil monitoring programmes in France. This new structure, called Scientific Group about Soils (GIS Sol) is constituted by the Ministries of Agriculture and Environment, the French Institute of Environment (IFEN), the organisation about environment protection and energy control (ADEME) and INRA. The Soil Survey Staff of France became then a single unit within INRA, the Infosol Unit, with the aim to realise the actions of the GIS Sol.
The objective of the GIS Sol is to develop an information system about the spatial distribution of French soils and the evolution of their properties. The two main priorities are the ‘Regional Soil Survey’ programme with the objective to have a complete coverage of France by 2010, and the development of a Soil Quality Monitoring Network.
This will be made possible with the help of some public and private organisations that are partners in these programmes: research institutes and universities, professional organisations, land development companies, etc.
The aim of this paper is to give an overview of the national soil mapping and soil monitoring programmes in France and their present state of progress.
The soil mapping programmes in France have been re-organised in a single multiscale information system called I.G.C.S. (survey, management and protection of soils). This programme can be subdivided in three main sub-programmes following the level of applications of the soil surveys:
The ‘Regional Soil Survey’ (R.R.P.), the aim of which is to provide soil information for regional decision makers;
• • •
The ‘Pedological Map of France’ (C.P.F.), that forms the basis for detailed research of soil spatial variability in representative areas; The ‘Reference Area’ (S.R.), the objective of which is to undertake detailed soil mapping at a local level on representative areas and for specific application purposes.
The objective of the ‘Regional Soil Survey’ (R.R.P.) programme is to develop geographical databases on soils that could give information
about the nature, locality and properties of soils at a regional level for decision makers. This programme was launched in 1990 by the Ministry of Agriculture (Jamagne et al., 1995). The geographical precision of data must support mapping at a scale of 1:250,000 (Bornand et al., 1989).
Up to now, two Regions and eight Departments have been completed, and soil survey has been done in 18 Departments on which computerisation is on-going (Figure 1). Soil survey is ongoing in sixteen Departments and will begin in 2004 in another Region and three Departments.
A test of data transfer to the European system is under way in the Côte-d’Or Department in Burgundy (Finke et al., 1998).
The ‘Pedological Map of France’ (C.P.F.) programme constitutes the first national programme of soil mapping, which led to the creation of the Soil Survey Staff of France in 1968 (Jamagne et al., 1995). Its first objective was to have a complete coverage of the French territory by soil maps at a scale of 1:100,000. Considering the difficulty to fulfil such an objective, it was decided to re-orient the C.P.F. programme giving preference to the formalisation of spatial distribution patterns of soils within areas considered representative of the main French soil systems. This will be done through three main actions:
1. To store the available information, including means to computerise the existing and on-going soil maps and accompanying notes to avoid loss of knowledge;
2. To realise soil surveys of insufficiently known areas, to have a complete review of the French soil systems (King and Saby, 2001);
3. To develop scale transfer methods to be able to use the information from these areas on the areas surveyed at a broader scale.
Up-to-now, 22 maps at a scale of 1:100,000 have been published and 13 maps are being prepared (Figure 1). Computerisation is ongoing for 14 maps, and soil survey is ongoing for a further 5 maps.
In the ‘Reference Area’ (S.R.) programme, soil survey at very high resolution (1:5,000 to 1:10,000 scale) is performed on small areas representative of specific soil systems, for a specific application, i.e. drainage, irrigation, waste spreading, etc. (Favrot, 1987; Cam et al., 2003). The detailed characterisation of the nature and the properties of soils in the reference area supports the definition of
a soil typology and relative practical recommendations for soil use. The ‘Regional Soil Survey’ is then used to define the region where the results of the reference area can be extrapolated (Lagacherie et al., 2001; Oballos and Lagacherie, 2003). It is finally an important tool for helping local people in identifying in the field the type of soil and in choosing the appropriate practice. The Soil Geographical Database of France at a scale of 1:1,000,000, that has been revised in the framework of European projects (Jones et al., 1998; Le Bas et al., 1998a), constitutes the present synthesis of the knowledge about spatial variability of soils for the whole of France. When complete, the Regional Soil Survey will be used to update the Soil Geographical Database of France at 1:1,000,000 scale.
In forested areas, a network was created more than 15 years ago, in the framework of the International Concerted Programme about impacts of atmospheric pollution on forests (ICP Forest). This monitoring programme is based on measurements realised at two levels. The first level is constituted by a 16km by 16km grid, on which soil quality measurements have been undertaken since 1994 to assess the soil chemical status and the vulnerability of the soils to air pollution (Vanmechelen et al., 1997).
In France, the level I represents 540 plots covering the wide range of ecological conditions observed in French forests (Badeau et al., 1999). Beyond the single description of chemical soil status required for ICP Forest, a very detailed ecological description for each plot was undertaken resulting in one of the most important datasets ever obtained in France on forest ecology.
In 102 plots of this level I network, a long-term monitoring system for forest ecosystems called RENECOFOR was created by the National Forest Office (ONF) in 1992 constituting the second level of ICP Forest in France (Ulrich, 1995). The objective of this second-level network is to determine the key factors of the functioning of forest ecosystems.
Two soil profiles are systematically studied and analysed for each plot. A set of parameters is monitored each year following a standard sampling scheme. With respect to the ‘Catenal’ sub-system (total acid load of atmospheric origin), atmospheric deposits have been measured in 27 parcels since
Figure 1: State of progress in 2003 of C.P.F. and R.R.P. programmes.
1993, and measurements are conducted on soil solutions taken from 20 to 70cm depth from 17 parcels. This network has shown the importance of deposits of nitrogen (from 4 to 15kg/ha/year) by rain.
In 1983, the Ministry of Environment created a ‘Soil Quality Observatory’ (O.Q.S.), the aims of which were to assess the present state of soils, and to monitor their changes for improvement and implementation of a soil protection policy (Martin, 1993). In spite of the important methodological contribution of this programme, its results were disappointing. An analysis by several organisations in 1998-1999 of the difficulties encountered in the O.Q.S. programme led to a proposition for a new monitoring programme.
This programme was launched in 2000 (Arrouays
et al., 2003) and is based on several actions:
Development of a network of sites on which to have a spatial assessment of changes for France: the Soil Quality Monitoring Network (R.M.Q.S.);
Creation of several research sites on which detailed studies about the processes involved could be undertaken by researchers;
Use of soil and land use information with GIS to define models and pedotransfer functions.
A study has been undertaken to define the most representative configuration for the Soil Quality Monitoring Network (R.M.Q.S.) for a reasonable cost (Arrouays et al., 2001b). A network based on a 16km by 16km grid representing 2,150 sites for non-forested areas has been chosen (Figure 2). It is a representative sampling of the main soil systems and land uses in France. This configuration has the advantage of being compatible with the ICP Forest grid. New measurements for each plot every 5 years have been foreseen. All the analyses are performed in only one laboratory from INRA. For each site, a set of analyses (particle-size distribution, bulk density, C, N, pH, trace elements, etc.) and a complete description of the profile are performed, also with information about the past activities, the environment, etc. All the samples are stored in a specific place for conservation. New analyses can then be realised on the samples in the future.
The objective is to establish all the sites by 2007.
The computerisation of the soil survey data leads to the development of a specific information system that stores, in a GIS, the spatial location of surveyed data (polygons for mapping areas, points
Figure 2: Location of monitoring sites of the R.M.Q.S and ICP Forest programmes.
for profile data) and in a specific database, called DONESOL, the descriptive information for soil mapping units, soil typological units and horizons, and the description and the analyses for the profiles (Gaultier et al., 1993). This structure is common for all the soil surveys whatever their resolution.
DONESOL also stores information about soil studies performed on French territory (location, type of study, authors) and about the soil specialists in France (Favrot, 1994; Favrot, 1997). This information will soon be available through an Internet site that is under development.
DONESOL is presently being modified to be able to store also all the data coming from the Soil Quality Monitoring Network (R.M.Q.S.). This will maintain compatibility between the data coming from soil surveys and those coming from the monitoring programme.
Other databases have been prepared in conjunction with, or in parallel to, the DONESOL database. Generally, these databases have been compiled in the context of specific research projects. They deal with trace elements, carbon content, and water
properties of soils. Their purpose is to acquire reference data about French soils to be able to estimate natural trace element contents, carbon stocks or pedotransfer functions for hydrodynamic properties.
A specific work is undertaken to store in a specific database, called the Soil Analyses Database (BDAT), the soil analyses carried out by private laboratories in France (Walter et al., 1997; Schvartz et al., 1998). About 250,000 analyses are realised each year, mainly for farmers.
Considering the amount of analyses and their diversity of origin, they represent a great source of information about the variability of topsoil horizons in cultivated areas both in space and time. They include some parameters that are influenced mainly by human activities like carbon content, pH, nutrient content, etc.
All the private laboratories, having an agreement with the Ministry of Agriculture were asked to deliver the results from their analyses. A first collection of data was performed for analyses realised between 1990 to 1994, and 300,000 analyses were then collected.
Figure 3: Organic matter content of the surface horizon in cultivated areas, extracted from the BDAT (District statistics for the period 1990-1994)
A second data collection is being undertaken now for the analyses performed between 1995 and 2000. The analyses are referenced spatially to the commune from where the sample was taken. Statistical analyses are performed at the county level. Each variable can be expressed in the form of maps or statistical tables and these documents have confirmed spatial distributions that are often known but have never been quantified, especially for variables that are difficult to determine in conventional mapping work (Figure 3).
Use of Existing Soil DataMuch effort has been directed to convince the national authorities of the importance of taking into account soils for many purposes. This led to the creation of the GIS Sol that gives a boost to soil survey and to soil monitoring activities in France. However, for many of these activities, and
particularly for soil survey, national funding is not sufficient and other sources of financial support have to be found (regional authorities, professional organisations, etc.). One way to convince these organisations to finance these activities is to demonstrate how soil data can be used.
At the national level, the Soil Geographical Database of France, at 1:1,000,000 scale, represents the only source of data that covers the whole country. In spite of its low resolution, this database has been used for many purposes such as erosion risk assessment - see Figure 4 – (Le Bissonnais et al., 2002), assessment of grassland production (Donet et al., 2001) and estimation of carbon stocks in soils (Arrouays et al., 2001a).
At the regional or local level, many applications are undertaken. A recent study was realised asking
soil data for which they were responsible. The first results of this study show that the applications are mainly for agricultural or agri-environmental purposes: crop production, irrigation management (Cousin et al., 1998), risk of nitrate or pesticide leaching (Saby et al., 1999), erosion risk assessment, fertilising with urban composts (Legros et al., 1991), etc., and are increasing from year to year. There is also an increasing diversity of users but generally with a lack of ability to use soil data directly.
For 80% of the demands, users ask to have thematic data. A great effort is being undertaken to
develop tools that can help soil data users. One important research field in that domain concerns pedotransfer functions that allow estimation of non-available information from soil survey data, particularly for deriving input soil variables to models (Donet et al., 2001; Bruand et al., 2003). Work is also undertaken to give information to users about uncertainties, especially with the development of methods using geostatistics, fuzzy logic, etc. (Lagacherie et al., 1997; Le Bas et al., 1998b; Cazemier et al., 2001).
Figure 4: Maps of seasonal erosion risk in France.
Regional soil survey is continuing in order to obtain exhaustive and integrated information for the whole France. The scale of 1:250,000 is appropriate to answer users’ needs at national or regional level. However, such a scale is insufficient to respond to all kinds of demands that are highly varied and require greater precision. To respond to this demand for precise information, considerable resources are needed, but at this time,
no national plan is foreseen to allocate the necessary resources. It is thus necessary to develop tools that could help detailed soil survey or that could fill in the gaps.
One way was proposed through the new orientation of the C.P.F. programme, which aims to develop a knowledge base about representative soil systems and their functioning, and scale transfer methods that enable local organisations to apply this knowledge to their area of interest. Another way, mainly to answer to the increasing
needs for detailed soil surveys at the level of agricultural plots, is to develop the use of new techniques like spatial positioning and its use with appropriate agricultural techniques (precision farming), geophysics and digital elevation models (Chaplot, et al., 2001; Bourennane and King, 2003; Michot, et al., 2003).
Concerning soil monitoring, the creation of the R.M.Q.S. network is an efficient tool that could give information about the status of soil quality and its evolution. But, monitoring needs to have several measurements at the same place but at different time steps. For the moment, only one series of measurements has been done. It is thus necessary to have the resources to undertake new series of measurements for the R.M.Q.S. sites and also for forest sites. These two networks will give an overview of the evolution of soil quality but will not give information on the processes involved in such evolution.
It is thus necessary to extend research on specific sites for analysing specific processes. In this context, a research programme (GESSOL) whose
aim is to establish the scientific tools and bases to assess, monitor and even restore soil quality, was launched by the Ministry of Environment. First results were presented in 2002 (AFES, 2003) and a new programme was launched in 2004 in order to estimate better the impacts of agricultural practices on soil and water qualities.
Finally, it is recognised that all current or future programmes will be of interest only if the data gathered are distributed as widely as possible and in the most instructive manner possible. This implies the continuation of research in the field of combining spatial data and in that of error propagation when different data sets are combined. In addition, there is a need to develop methods for structuring and distributing information, in particular using modern computer technologies (Web, CD-ROM). It is also necessary to obtain more information on user needs in order to develop the tools that can most efficiently respond to these needs.
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