# Methodology of the OZCAR DEDMOS Transversal Workshop Ecological determinants of organic matter and water dynamics in the Critical Zone at the scale of the OZCAR network: from earthworm to database

Priscia Oliva, Eva Escadeillas, E. Kaiser, Quentin Lasman, H. Pradalier, Pascal Jouquet, David Sebag, Isabelle Braud

<figure><img src="image_1.png" /></figure>

## To cite this version:

Priscia Oliva, Eva Escadeillas, E. Kaiser, Quentin Lasman, H. Pradalier, et al.. Methodology of the OZCAR DEDMOS Transversal Workshop Ecological determinants of organic matter and water dynamics in the Critical Zone at the scale of the OZCAR network: from earthworm to database. 2024. [hal-05536319](https://hal.science/hal-05536319v1)

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Submitted on 4 Mar 2026

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# Methodology of the OZCAR DEDMOS
Transversal Workshop

Ecological determinants of organic matter and water dynamics in the Critical
Zone at the scale of the OZCAR network: from earthworm to database

Version 2, July 2024

P. OLIVA, E. ESCADEILLAS, E. KAISER, Q. LASMAN, H.

PRADALIER, P. JOUQUET, D. SEBAG, I. BRAUD

2024, English translation : I. Braud with the use of DeepL

The DEDMOS system aims to combine various complementary approaches to address the question of the ecological determinants of the dynamics of organic matter and water in soils on the scale of the OZCAR network. The protocol for sampling and in situ measurements is based on the protocols<fnref n="1" /> used by the RMQS<fnref n="2" /> and RMQS biodiv. It is based on setting up a soil sampling surface, 5 specific sampling and in-situ test zones and a 1m-deep soil pit (Figure 1). The "typical" sampling area corresponds to a 10 m x 10 m square divided into 25 elementary plots (2 m x 2 m).

<figure><img src="image_3.png" /><figcaption>Figure 1 – DEDMOS sampling strategy</figcaption></figure>

<footnote n="1">¹ https://www.gissol.fr/wp-content/uploads/2018/03/Manuel_V_Num2.pdf</footnote>

<footnote n="2">² RMQS (Réseau de Mesure de la Qualité des Sols - Soil Quality Measurement Network)
https://www.gissol.fr/le-gis/programmes/rmqs-34</footnote>
# Sheet 1. Setting up the sampling surface

## Equipment:

- Decameters x3

- Markers (minimum 4) for the corners of the surface

- Landmark (minimum 30)

- GPS with centimeter accuracy

<figure><img src="image_4.png" /></figure>

Durée : 30'

2 personnes

## Procedure:

To set up this system, reference points corresponding to the corners of the 10m x 10m sampling area and to the specific sampling and in-situ test zones must be established using decameters. The location of these points is accurately measured using a centimeter-scale GPS. The location of the sampling area must be chosen according to the following criteria: the area must be homogeneous and characteristic of the plot (photo 1), located sufficiently far from the edges and undisturbed (human activity, erosion patterns, etc.).

<figure><img src="image_5.png" /><figcaption>Photo 1 – Overall view of two sampling areas carried out on an uncultivated plot at Auradé (Gers, France) - The heterogeneity of the plot meant that several sampling devices had to be set up (Photographic credits P. Oliva)</figcaption></figure>
The shape of the sampling area can be adapted to the area to be studied but must be around 100m² and allow a grid to be set up so that 25 +/-1 sampling points can be identified.

The sampling area can be set up using decameters or a centimetric GPS. Many situations are incompatible with the use of GPS (steep slopes, off-grid, vegetation cover), which is why we prefer to use decameters. To set up the 10m x 10m square sampling area using a decimeter, 1/ position the first two reference corners (1 and 2) 10m apart and 2/ position corner 3 using two other decameters, 10m from corner 2 and 14.14m (diagonally) from corner 1. The same principle is used to position corner 4. Rather than dividing the surface into 25 sub-plots of 2m x 2m (square meshes), it is more practical to position the studs in the center of the mesh (photo 2), respecting the distances to the edges of the device and between studs. To do this, position two decameters along two opposite sides of the surface and stretch out the third decimeter in line with the future grids to position them.

<figure><img src="image_6.png" /><figcaption>Photo 2 - Overall view of a 10m x 10m sampling area on an uncultivated plot of land on the Toulouse III University campus, with the 25 stakes in the centre of the grid (Photo credit: P. Oliva).</figcaption></figure>
# Sheet 2. Taking composite soil samples

## Équipement :

- Edelman-type hand auger adapted to soil type and graduated

- Knife

- 2 plastic buckets with handles (ideally grape harvesting buckets)

- Mixing tub and shovel

- Nitrile gloves

- Plastic bags, markers

- Demineralized water, paper towels

<figure><img src="image_7.png" /></figure>

Durée : 30'

2 personnes

## Procedure :

Composite soil sampling must be carried out once the sampling depths have been defined, which may correspond to the depths of appearance/disappearance of the main soil horizons or to a specified sampling depths. The equipment must be cleaned with demineralized water and dried before sampling begins and between each composite sample. Samples are taken semi-randomly with a hand auger within a 1 m radius of each staking (photo 3a). The auger must be graduated beforehand (photo 3b). The composite sample is based on individual samples that are identical in terms of depth and volume, and which must therefore be 'calibrated' using the same procedure (photos 4a to 4f): only the part of the soil inside the bucket is kept, removing any overflow and the tip (waste). In order not to disturb the soil in the sampling area, it is preferable to use two buckets: one for the "composite" samples and one for the "waste" samples.

<figure><img src="image_8.png" /></figure>

Photos 3a – Overall view of the composite samples taken from a 10m x 10m sampling area. 3b - Overall view of the graduated auger (Photo credits: P. Oliva).
<figure><img src="image_9.png" /></figure>

Photos 4a à 4f -calibration procedure for taking composite soil samples. Once the auger bucket has been extended, use the knife to remove the part of the soil protruding from the bucket on either side (4a) and the tip (4b). The first bucket, i.e. the first 20 cm of soil, can be recovered without further handling. However, for deeper samples (20cm and more), the top part of the sample, which corresponds to the filling of the hole when the auger is handled, must be systematically removed. Therefore, use the knife to remove 1/3 of the bucket (4c), and calibrate the sample by removing the excess (4d) and the tip (4e) before placing the sample in the sampling bucket. The "waste" bucket is used to recover the deep soil material and avoid "disturbing" the surface soil in the sampling area (Photographic credits P. Oliva).

Once all the points (25 +/- 1) have been taken for a given depth, the composite sample is carefully mixed in a clean container before being crumbled and bagged. Gloves should be worn during crumbling, especially if microbiological analysis is planned. If it is necessary to take only a representative aliquot, the sample can be quartered in the field, but as a general rule it is dried and quartered later in the laboratory.

Note that certain factors can make it difficult to produce a composite sample: the presence of coarse elements, compacted soil, soil that is too dry or waterlogged soil. In the case of blockages caused by coarse elements or compacted areas, it is important to note the depth of the blockages in order to assess the representativeness of the final sample. If the soil is too dry or too waterlogged, it may not be possible to take a sample.
# Sheet 3. Sampling to measure apparent density using the calibrated cylinder method in a soil pit

## Equipment:

- Calibrated 250 or 500cm3 cylinders with monobloc cylinder holders, matrix or other "striking" systems

- Nylon hammer

- Tape measure or folding ruler

- Knife or small saw, secateurs

- Mason's trowel and spatulas

- Bags, markers

<figure><img src="image_10.png" /></figure>

Durée: 10' en moyenne par densité
1 personne

## Procedure:

During digging, one side of the pit should be protected from trampling. The cylinders are deployed from the surface, after cutting the vegetation, from a flat surface (photo 5a). They are driven fully into the ground using a die and hammer (5b and 5c). The cylinders are extracted from the profile using the trowel and knife to keep the sample intact (5d and 5e). Using the knife or a small saw, the soil contained in the cylinder is carefully levelled. The contents can be left in the cylinder or emptied into a labelled bag if the number of cylinders is insufficient to characterize the soil. In the laboratory, the sample is weighed and dried in an oven at 105°C until the weight of the sample has stabilized, at which point the bulk density can be calculated.

<figure><img src="image_11.png" /></figure>

Photos 5a à 5e - steps in taking a soil sample using the calibrated cylinder method along a profile in a soil pit (Photo credits: P. Oliva).

The number of samples of apparent density taken at different depths depends on the number and depth of the composite soil samples previously taken (see sheet 2). For each composite sample, a minimum of 3 samples must be taken to measure bulk density. They should be spread over the entire depth of interest, avoiding taking samples that straddle two distinct horizons.
# Sheet 4. The installation of "BARBER" jars for sampling epigeous fauna

## Equipment:

- Clear water (tap, bottle of drinking water)

- Odourless and colourless washing-up liquid

- Home-made transparent "roof" system

- Auger

## Procedure :

Within each sampling and test zone, a hole the depth of the pot is dug using an auger (photo 6a). The position of the hole must take the local topography into account. It is preferable for the pot not to be located in an area where water is running off or in a hollow in the event of rain, as this could lead to overflow and the loss of the trapped organisms. The empty pot is then placed in the hole, ensuring that the edges of the pot do not protrude (photos 6b and 6c). A mixture of water and washing-up liquid is added. Depending on the weather forecast, a transparent roof can be added to prevent the pot from overflowing in the event of rain (photo 6d). The "BARBER" pots are deployed for at least 24 hours and recovered so that the epigeous macrofauna trapped can be identified in the laboratory.

<figure><img src="image_12.png" /></figure>

Durée : 10' par pot pour l'installation

1 personnes

Nécessite de revenir sur le site (24h minimum)

<figure><img src="image_13.png" /></figure>

Photos 6a à 6e – steps for setting up a "BARBER » pot - 6a making a hole with an auger - 6b and 6c installing the empty pot flush with the surface, taking care not to drop any soil inside before filling it with a mixture of water and washing-up liquid - 6d installing a transparent rain cover to avoid creating a bias for the organisms (Photographic credits P. Oliva and Q. Lasman).

As the "BARBER" pots were deployed over a minimum period of 24 hours, care should be taken to carry out the other samples (TSBF type spade tests, porosity columns, etc.) after the "BARBER" pots had been recovered, so as not to disturb the macrofauna in the vicinity.
# Sheet 5. Counting and identifying soil fauna using the TSBF method

## Equipment:

- Flat shovel, spade x2

- Bins

- Knife

- Folding ruler,

- Equipment for sorting organisms (trays, tongs, gloves, etc.)

- Recovery bottle, marker

## Procedure:

Within each sampling and test zone, a pre-trench 30 cm wide and 30 cm deep is first made (photo 7a). A block 25x25 cm in area and 30 cm deep is then spaded on the cleanest, vertical side of the trench (photo 7b).

<figure><img src="image_14.png" /></figure>

Durée : 30' à 2h par test

2 personnes

Prévoir un système d'abris par temps pluvieux

<figure><img src="image_15.png" /></figure>

Photos 7a à 7e - Steps in carrying out the TSBF protocol - 7a making a trench - 7b to 7d individualising and sampling a block 25cm square and 30cm deep - 7e cutting into two sub-blocks 0-10 and 10-30cm deep and 7f sorting and sampling organisms (Photographic credits Q. Lasman).
The block is then extracted using the two bits and placed in a tray (photos 7c to 7e). Using a knife and a folding metre, the block is divided into 2 sub-blocks, one 0 to 10 cm deep and one 10 to 30 cm deep. At this stage, it's important to check that no organisms emerge and change block. The sub-blocks are then placed in two different tanks, and each sub-block is 'stripped' and any living organisms found in it are collected, photographed and identified (photo 7f). Particular attention is paid to the ecological categories to which the earthworms belong: epigeic, endogeic and anecitic (photo 8).

<figure><img src="image_16.png" /><figcaption>Photo 8 – Example of an anecium earthworm of the family Vermicidae (Photo credits: P. Oliva).</figcaption></figure>
# Sheet 6. Measurement of surface infiltration rate using the beerkan test

## Equipment:

- Thin-walled, rigid cylinders 20 to 25 cm in diameter and at least 10 cm high

- 400 or 500 mL beakers x 10

- Cans of water

- Hammer, board, level

- Pruning shears, pair of scissors

- Stopwatch

- Notebook and pens

<figure><img src="image_17.png" /></figure>

## Materials and equipment for measuring auxiliary data

- Small boxes for taking samples to estimate the initial water content of the soil. If the volume of the cylinder is known, the dry density can also be estimated.

- Calibrated cylinders of 250 or 500 cm³ with monobloc cylinder holders, dies or other 'striking' systems.

- Bags for soil samples (freezer bags)

- Permanent markers for numbering soil samples

- Nylon hammer

- Tape measure or folding ruler

- Knife or small saw, pruning shears

- Mason's trowel and spatulas

- Small shovels for taking samples

## Procedure:

Several additional measurements are necessary to document the infiltration experiment (not shown in the video):

- Initial soil water content

- Soil sample for particle size distribution analysis

- Final soil moisture content and dry bulk density

## Initial measurement of soil moisture and soil sampling:

- Take a soil sample near the location where the infiltration experiment is being conducted and place it in a small box (whose empty weight you have determined), closing the box carefully to prevent evaporation. Once in the laboratory, the small box is weighed, dried in an oven for 48 hours at 105 °C, then weighed again to determine the gravimetric water content. We recommend using calibrated cylinders to perform this measurement as it allows the dry bulk density to be determined (even if it is less accurate than that estimated when the soil is wet, it is useful to have several estimates). Photo 9 shows an example of a small cylinder that can be used to collect this sample.
<figure><img src="image_18.png" /><figcaption>Photo 9: Illustration of a small cylinder used to determine the initial water content of the soil (photo credit, I. Braud)</figcaption></figure>

- Take a composite sample from the soil surface near the infiltration experiment site using small shovels. Place the soil sample in soil sample bags and write the identification number on the bag. Next, a soil analysis to determine particle size distribution should be performed on this sample. We recommend performing an analysis in five fractions: (<2, 2-20, 20-50, 50-200, 200-2000 µm) to obtain a better description of the particle size distribution.

The principle is to measure the speed at which water infiltrates the soil surface, for a 1cm depth of water, and iteratively repeat the measurement until a steady state is reached. Within each sampling and test zone, the choice of location for the cylinder is important, as it must be representative of the sampling surface and located in an area where the surface condition has been preserved (no trampling). Hollows, holes and cracks, which can be a source of bias, should be avoided. It is also important to ensure that the test is carried out on soil that has been cleared of obstacles to water infiltration by removing pieces of wood, litter and stones and by cutting the vegetation down to size (photo 10a, the plants must be cut but not uprooted). The 20 to 25 cm diameter cylinder is pressed a few centimeters into the ground (1 to 2 cm) using a board, hammer and level to ensure that it is horizontal (photo 10b). Make sure that there is good contact between the soil and the cylinder to avoid water leaking around the edges (photo 10c). The 10 beakers are first filled with the same volume of water, i.e. the volume corresponding to a 1cm depth of water, which depends on the size of the cylinder and is calculated using the formula $V = hπr²$ (photo 10d). The timer is started when the first beaker is emptied into the device. To ensure that the flow of water does not alter the surface (splash effect), it is recommended that the water flows over a circle of plastic film placed on the bottom and cut to the size of the cylinder or along the handle of the hammer placed across it (photo 10e). When the water has completely infiltrated, i.e. there is no longer any free water on the surface of the soil (photo 10f, soil in the process of drying out), the time is noted and the next volume of water is emptied in turn. This procedure is repeated until the infiltration regime becomes stable (constant infiltration time). The infiltration rate is determined by plotting the cumulative volume of water infiltrated as a function of time for the linear portion of the curve (constant slope).

## Determination of final water content and dry bulk density

Once all the remaining water has infiltrated, remove the cylinder and take a soil sample from the wet surface to obtain the final soil moisture content (using the same method as for the initial soil water content) and the dry bulk density using calibrated cylinders of 250 or 500 cm³ with monobloc cylinder holders, dies or other 'strike' systems. The sample is taken from the wet soil, as it is easier
to take than from dry soil. In addition, the use of a calibrated cylinder allows the dry bulk density to be determined at the same time, which will be used to convert the gravimetric water content into volumetric water content (see the sheet 3 on bulk density measurement for sampling).

<figure><img src="image_19.png" /><figcaption>Photos 10a à 10f – stages of the beerkan protocol for measuring surface infiltration velocity (Photo credits: P. Oliva and Q. Lasman).</figcaption></figure>

An interface in Scilab ([https://www.scilab.org/](https://www.scilab.org/)) for applying the main BEST methods (BEST Steady, Intercept, and Slope) is available for analysing infiltration experiments ([https://bestsoilhydro.net/downloads/](https://bestsoilhydro.net/downloads/)).

Further information on the BEST algorithm can be found at: [https://bestsoilhydro.net/](https://bestsoilhydro.net/)
A special version of the method called BEST-WR (Di Prima et al., 2021³) is also available in cases of suspected water repellency.

<footnote n="3">³ Di Prima, S., Stewart, R. D., Abou Najm, M. R., Ribeiro Roder, L., Giadrossich, F., Campus, S., Angulo-Jaramillo, R., Yilmaz, D., Roggero, P. P., Pirastru, M., and Lassabatere, L.: BEST-WR: An adapted algorithm for the hydraulic characterization of hydrophilic and water-repellent soils, Journal of Hydrology, 603, 126936, https://doi.org/10.1016/j.jhydrol.2021.126936, 2021.</footnote>
# Sheet 7. Sampling of porosity columns

## Equipment:

- Cylinder (PVC, metal) ideally 15cm in diameter and height

- Striking board or die

- Mallet or hammer

- Trowel, knife

- Plastics, rubber bands, packing tape

<figure><img src="image_20.png" /></figure>

Durée : 10' par prélèvement

1 personne

Prendre des précautions pour le transport

## Procedure:

In each sampling and test zone, a cylinder is pushed completely into the soil using a matrix or a board and a hammer. It is recommended that this sample is taken close to the pre-trench dug as part of the TSBF spade test, to facilitate extraction. The trowel and knife are used to extract the porosity column at the bottom (similar to the extraction of density cylinders). The column is then protected and sealed using thick plastic film or bags, elastic bands and scotch tape to limit degradation. Particular care must be taken when transporting the column so as not to affect its porosity (settling, cracking, etc.). In the laboratory, the column is quickly placed at -20°C for 24 hours to prevent any organisms in the column from changing the porosity while waiting to be analyzed by tomography.

<figure><img src="image_21.png" /></figure>

Photos 11a et 11b – Sampling soil columns to study porosity using tomography (Photo credits: H. Pradalier and Q. Lasman).
# Sheet 8. Visual assessment of soil structure using the VESS test

## Équipement:

- Spade

- Measuring tape

- Tarpaulin or large tub

- VESS* determination key (available free online)

## Procedure:

Ideally, the soil should be neither too dry nor too wet, and the tillage should not be too recent. Choose an area that is representative of the surface, or repeat the tests if there is too much heterogeneity. In all cases, it is advisable to repeat the tests in order to assess a plot in a representative manner, which is why it is recommended to carry out a VESS test on each of the 5 sampling zones, as an extension of the small trench carried out for the TSBF. The first step in a VESS test is to make a pre-hole so that a slice of soil about 5 to 10cm thick, 20cm wide and 30cm deep can be easily extracted, the equivalent of a spade blade. This slice of soil is then carefully placed on a tarpaulin or in a tray to isolate it from the soil and make it easier to describe. The analysis begins by identifying the visible horizons and their depths in the first 30 centimeters. An initial estimate of the overall structure is then made. Next, the block is opened with the hands and the aggregates uncovered. The determination key is used to score each soil horizon individually according to the various VESS test criteria (structure, compactness, size and shape of aggregates or clods, root behavior, etc.). This gives us an average score for each horizon, which enables us to calculate a weighted overall score for the block using the formula:

$$ \text{Block score} = [(\text{layer}_1 \text{ thickness} \times \text{layer}_1 \text{ score}) + (\text{layer}_2 \text{ thickness} \times \text{layer}_2 \text{ score}) + (\text{layer}_n \text{ thickness} \times \text{layer}_n \text{ score})] / \text{total block thickness} $$

<figure><img src="image_22.png" /><figcaption>Photos 12a à 12c - Carrying out the VESS test - 12a depositing the slice of soil in a tray - 12b identifying the horizons - 12c evaluating and scoring the block according to the VESS criteria (Photographic credits H. Pradalier and Q. Lasman).</figcaption></figure>

<figure><img src="image_23.png" /></figure>

<footnote>* Baize et al., 2013 - Evaluation Visuelle de la Structure des horizons de surface des sols cultivés (VESS), traduction de la clé visuelle développée par Guimarães, R.M.L., Ball, B.C., and Tormena, C.A. (2011) adaptée de Boizard, H.et al., in Baize, D. et al., (2013)</footnote>

<footnote>Ball et al., 2007 - Ball B. C., Batey T., & Munkholm L. J. 2007. Field assessment of soil structural quality-a development of the Peerlkamp test.
Soil use and Management, 23(4), 329-337.</footnote>

<footnote>https://soin-de-la-terre.org/wp-content/uploads/GEODE_SOLS_VESS_A_Test_beche_Horizon_A_score-chart_FR_2018.pdf</footnote>