Soil monitoring network

Background

Our spatial soil descriptions and soil maps are based on a classification and determination of coherent soil units which only make sense on a certain scale. In France, the INFOSOL Service Unit at the INRA Centre in Orléans has produced not only a multi-scale Soil Inventory, Management, and Conservation programme (IGCS) but also a 10-year national soil quality monitoring programme called RMQS (Soil Quality Measurement Network) which collects data from 2150 sites across the country arranged in a 16 km x 16 km grid. The methods and protocols for the soil description and monitoring programmes were defined and standardised as part of the European ENVASSO Project (Environmental Assessment of Soil for Monitoring), which in turn is part of the EU's 6th Framework Programme for Research and Technological Development. The work carried out as part of this project has made it possible to establish Good Practice Guidelines for creating soil monitoring networks, whether as regards determining the spatialised network, identifying physical, chemical and biological parameters, or designing the sampling and storage protocol (site size and location, number of samples, vertical sampling etc.).

Aims

Reference values: typological approach

The purpose of obtaining reference values is to be able to determine soil quality in terms of physical, chemical, biological and pedological properties. The recommended approach is typological. Soil types are grouped into classes, and statistics are then calculated for the properties of the soils within each class (mean, standard deviation, median, percentiles etc.). The aim is to obtain standard or "reference" values for each of these parameters and to produce predictive models for each of the reference values which will be used to detect deviations.

Long-term monitoring: systematic approach

The best tools for implementing a long-term monitoring network are the systematic grid method and the standard RMQS protocol. However, although geological and geomorphological context are both important factors in soil studies, soil use is also very relevant. Indeed, the past and current usage of soil can affect its properties. In addition, soil usage may change over time.

Procedure/Method

The reference values for soil quality cover the full extent of the reference zone, which measures 240 km2. The programme has been carried out with the assistance of various partners from the INRA, the INPL/ENSAIA and the CNRS.

Obtaining the reference values and deploying the long-term soil quality monitoring system was done using a systematic network of sites distributed along a 1.5 km x 1.5 km grid pattern in line with the RMQS protocols (Jolivet et al., 2006). It also used a number of other sites to ensure a more suitable typological or stratified approach for compiling reference data (Baize, 1997; Collinet et al., 2004; Sterckeman et al., 2006). The soil quality reference values comprise pedological properties, and levels of organic and mineral contaminants and radioactive elements, as well as the soil's microbial diversity and mesofauna.

The protocol for setting up the sites, taking samples and identifying them was designed in collaboration with the various project partners, including soil experts, soil biologists, geochemists and soil monitoring specialists. The national "RMQS" protocol was adapted to the size of the area to be covered, taking account in particular of the various geological and geomorphological conditions. Although it was necessary to include a sufficient number of conditions to represent all the variations in soil quality caused by present or past usage of the land and even the effects of pollution, variations in parent (geological) material and in geomorphological conditions were not as important when it came to the soil properties to be analysed. The chosen strategy took into account these various limitations on surface and deep factors that determine soil quality. Two types of data collection point/site were therefore determined, in line with the diagram below (figure 3):

  • Level 1 sites, comprising a 20m x 20m "composite zone" sampling site (red) from which composite samples were taken (approx. 80 sites)
  • Level 2 sites, comprising a 20m x 20m "composite zone" sampling site (red), from which composite samples were taken and a soil pit (green) was dug in order to provide a comprehensive soil analysis, take cylindrical samples for measuring apparent density and collect samples of parent rock (approx. 60 sites).

The reference values include the main physical and chemical parameters which are used in particular to describe the "agricultural" quality of the soil, such as texture, structure, pH, moisture content and amounts of carbon, nitrogen and nutrients. These basic parameters are accompanied by an analysis of certain micro-contaminants (trace metals, PAH and PCB), excluding phytosanitary products.

Systematic network map (1.5 km x 1.5 km grid) for monitoring soil quality across the OPE reference zone, showing sites by sampling yearSystematic network map (1.5 km x 1.5 km grid) for monitoring soil quality across the OPE reference zone, showing sites by sampling year

In order to validate our representation of the main soil factors/soil usage across the grid, a comparison was made using the soil map (scale 1:50,000) and the CORINE Land Cover 2006 database (scale 1:100,000) created using satellite images (SPOT 4 and IRS) from 2006 at a resolution of 20 metres (description threshold 25 hectares).

Representation of the main soil factors/soil usage (absolute values)
Soil typeSoil usage - Corine Land Cover 2006 (expressed in hectares)Number of sites (1.5 km x 1.5 km grid)
ClassLSE Soil UnitRPFclassificationForestMeadowlandGCTotalForestMeadowlandGCTotal
Plateau soil (63% of the soil surface area) Unit 1: Brown rendzina and surface brown calcareous earth Rendosols 2530 965 7092 10666 11 3 39 53
Unit 2: Calcareous brown earth Calcisols 2052 63 1277 3392 12 - 5 17
Unit 3: Slightly bleached brown earth and slightly acidic bleached brown earth Brunisols 1048 3 627 1678 5 - 4 9
Hillside soil (25% of the soil surface area) Unit 4: Colluvial rendzinas Rendosols 1164 594 842 2626 6 4 2 12
Unit 5a: Locally hydromorphic calcareous brown earth Calcosols 120 466 1293 1943 1 1 4 6
Unit 5b: Colluvial calcareous brown earth Colluvial calcosols 77 13 159 249 - - - 0
Valley floor soil (9% of the soil surface area) Unit 6: Colluvial brown earth on dry valley floors Colluviosols 557 332 951 1855 3 1 3 7
Unit 7: Alluvial/colluvial brown earth on small valley floors Brown fluviosols 68 716 268 1091 - 4 - 4
Unit 8: Alluvial/colluvial brown earth on the floor of the Marne and Ornain valleys Brown fluviosols 28 402 32 481 - 4 - 4
Total 7649 3562 12550 24003 38 17 57 112
Representation of the main soil factors/soil usage (relative values)
Soil typePedagogical map x Corine Land Cover 2006 (percentage of represented surface area)Percentage of sites
ClassLSE Soil UnitRPF classificationForestMeadowlandGCTotalForestMeadowlandGCTotal
Plateau soil (63% of the soil surface area) Unit 1: Brown rendzina and surface brown calcareous earth Rendosols 10.5% 4.0% 29.5% 44.4% 9.8% 2.7% 34.8% 47.3%
Unit 2: Calcareous brown earth Calcisols 8.5% 0.3% 5.3% 14.1% 10.7% - 4.5% 15.2%
Unit 3: Slightly bleached brown earth and slightly acidic bleached brown earth Brunisols 4.4% 2.6% 7.0% 4.5% - 3.6% 8.0%
Hillside soil (25% of the soil surface area) Unit 4: Colluvial rendzinas Rendosols 4.8% 2.5% 3.5% 10.9% 5.4% 3.6% 1.8% 10.7%
Unit 5a: Locally hydromorphic calcareous brown earth Calcosols 0.5% 1.9% 5.4% 8.1% 0.9% 0.9% 3.6% 5.4%
Unit 5b: Colluvial calcareous brown earth Colluvial calcosols 0.3% - 0.7% 1.0% - - - -
Valley floor soil (9% of the soil surface area) Unit 6: Colluvial brown earth on dry valley floors Colluviosols 2.3% 1.4% 4.0% 7.7% 2.7% 0.9% 2.7% 6.3%
Unit 7: Alluvial/colluvial brown earth on small valley floors Brown fluviosols 0.3% 3.0% 1.1% 4.5% - 3.6% - 3.6%
Unit 8: Alluvial/colluvial brown earth on the floor of the Marne and Ornain valleys Brown fluviosols - 1.7% - 2.0% - 3.6% - 3.6%
Total 31.9% 14.8% 52.3% 100.0% 33.0% 14.7% 52.3% 100.0%

Soil mapSoil sampling and analysis methodSoil sampling and analysis method based on the RMQS protocol

(Source: RMQS Manual, 2006)

To avoid any positioning bias, all installations were laid out in a South-North orientation. Building the sampling and analysis site began with the creation of the sampling area. This was a 20m x 20m square divided into 100 sampling units each measuring 4m² (2m x 2m).

The soil pit at each Level 2 site was located 5 metres from the south end of the sampling area.

A general soil profile was obtained: usage, parent material, geomorphology, moisture regime etc.

This profile was completed with a diagram based on the STIPA file stating the name of the soil and its horizons (if possible in Soil Reference Values), and any profile differentiations or discontinuities. Finally, the profiles were accompanied by photographs, identified using a label showing the identification number (site details) and a depth scale.

Photography of the solum

General soil profile
DepthHorizon nameFull description: texture, colour, reaction to acid, structure, porosity, mechanical properties, streaks, coarse elements, moisture regime, coatings, features, biological activity etc.
0-25/30 cm LAca Sand-clay loam, brown (10YR32), calcareous, crumbly (5-10 mm) to particulate, loose to not very compact, porous; some calcareous pebbles and gravel (<5%), few roots; regular transition (4-5 cm)
25/30-65/70 cm S(g)ca Sand-clay loam, light beige (10YR42), calcareous, subangular blocky (10-20 mm), little compaction, porous; some rusty streaks; no pebbles, several roots; regular transition (5-6 cm)
65/70-90/100 cm Sgca Argillic-loamy sand to sandy clay, greyish yellow (25Y53), calcareous, angular blocky (20-30 mm) to prismatic (50-80 mm), little compaction to compact, porous; several rusty streaks; no pebbles, few roots; rippled transition (10 cm)
90/100-120/130 cm Goca Loamy-sandy clay, yellowish grey (25Y52), calcareous, massive to prismatic (80-100 mm), compact, slightly to moderately porous; several grey-rusty streaks; some calcareous gravel (1-2%), few or no roots; rippled transition (10 cm)
120/130-150 cm Cgca Sandy clay, yellowish greyish rusty hue (25Y54), highly calcareous, massive, compact, moderately porous; several rusty streaks; several calcareous pebbles (40-60% and more), no roots.

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