# Assessing carbon stock changes in French top soils in croplands and grasslands: comparison of fixed depth and equivalent soil mass.

José-Luis Munera-Echeverri, Manuel P Martin, Line Boulonne, Nicolas P. A. Saby, Dominique Arrouays

► To cite this version:

José-Luis Munera-Echeverri, Manuel P Martin, Line Boulonne, Nicolas P. A. Saby, Dominique Arrouays. Assessing carbon stock changes in French top soils in croplands and grasslands: comparison of fixed depth and equivalent soil mass. 22. World Congress of Soil Sciences, Jul 2022, Glasgow, United Kingdom. 2022, 10.1111/ejss.12002. hal-04492722

HAL Id: hal-04492722

https://hal.inrae.fr/hal-04492722

Submitted on 6 Mar 2024

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Distributed under a Creative Commons Attribution 4.0 International License
# Assessing carbon stock changes in French top soils in croplands and grasslands: comparison of fixed depth and equivalent soil mass.

José-Luis Munera-Echeverri, Manuel P Martin, Line Boulonne, Nicolas P. A. Saby, Dominique Arrouays

► To cite this version:

José-Luis Munera-Echeverri, Manuel P Martin, Line Boulonne, Nicolas P. A. Saby, Dominique Arrouays. Assessing carbon stock changes in French top soils in croplands and grasslands: comparison of fixed depth and equivalent soil mass. 22. World Congress of Soil Sciences, Jul 2022, Glasgow, United Kingdom. 2022, 10.1111/ejss.12002. hal-04492722

HAL Id: hal-04492722

https://hal.inrae.fr/hal-04492722v1

Submitted on 6 Mar 2024

HAL is a multi-disciplinary open access
archive for the deposit and dissemination of sci-
entific research documents, whether they are pub-
lished or not. The documents may come from
teaching and research institutions in France or
abroad, or from public or private research centers.

L'archive ouverte pluridisciplinaire HAL, est
destinée au dépôt et à la diffusion de documents
scientifiques de niveau recherche, publiés ou non,
émanant des établissements d'enseignement et de
recherche français ou étrangers, des laboratoires
publics ou privés.

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

Distributed under a Creative Commons Attribution 4.0 International License
# Assessing carbon stock changes in French top soils in croplands and grasslands: comparison of fixed depth and equivalent soil mass.

<figure><img src="image_2.png" /></figure>

INRAO
science for people, life & earth

Munera-Echeverri JL¹, Martin M¹, Boulonne L¹, Saby N¹, Arrouays D¹.

¹INRAE, InfoSol, 45075, Orléans, France

## Introduction

* We use data from the first (2000-2009) and second (2016-2027) campaign of the French soil quality monitoring network (RMQS) to compare soil organic carbon (SOC) stock changes based on equivalent soil mass (ESM) and fixed-depth (FD) in top soils (30 cm depth) in croplands and grasslands.

## Materials and methods

### Soil sampling

* Sites were selected based on the availability of data of the second campaign, and where the soil physical parameters were determined by the cylinder method in both campaigns.

* Composite soil sample for carbon analysis were taken from a 400 m² systematic unaligned grid every 4 m (Figure 1A).

* Soil pit adjacent to the grid. Three cylinders (500 cm³) were used estimate bulk density (BD) and coarse fragments (CF) at 0-30cm (Figure 2 B). Time between campaigns: 7-16 years.

<figure><img src="image_3.png" /><figcaption>Figure 1. A) Composite sampling and adjacent pits. B) Soil pit for bulk density and coarse fragments. From Jolivet et al. 2018.</figcaption></figure>

### Stocks and equivalent soil mass calculation

* SOC stock FD (Mg ha⁻¹) = BD * depth * SOC conc * (1-CF/100) / 10

<figure><img src="image_4.png" /><figcaption>Figure 2. Principle behind the evaluation of SOC stock changes based on equivalent soil mass and fixed depth. Taken from Wendt & Hauser 2013.</figcaption></figure>

### Statistical analyses

* Linear mixed model fit by residual maximum likelihood (REML)

* Student test corrected for spatial autocorrelation (Moran Index)

## Results

### Data inspection

* Sites distributed in a large proportion of France (Figure 3 A).

* Good correspondence of SOC content and CF between campaigns, and less good for BD (Figure 3 B,C, and D).

<figure><img src="image_5.png" /><figcaption>Figure 3. A) Spatial distribution of the sites. B) Soil organic carbon content, C) coarse fragments, and D) bulk density of RMQS 2 as a function of the values of RMQS 1 (black lines). Red lines are 1:1.</figcaption></figure>

* ESM slightly improves the prediction of SOC stocks of the second campaign compared to FD (Figure 4 & table 1).

<figure><img src="image_6.png" /><figcaption>Figure 4. SOC stocks of RMQS 2 estimated based on A) ESM and B) FD as function of SOC stocks of RMQS 1 (black lines). Red lines are 1:1.</figcaption></figure>

<table><caption>Table 1. Model comparison of SOC stocks in the RMQS 2 as a function of the stocks in RMQS 1 based on ESM and FS.</caption><thead><tr><th></th><th>Intercept</th><th>Slope</th><th>Res. s.e</th><th>BIC</th><th>AIC</th><th>logLik</th><th>R2</th></tr></thead><tbody><tr><td>ESM</td><td>7.261</td><td>0.863</td><td>6.581</td><td>551.632</td><td>539.849</td><td>-264.924</td><td>0.944</td></tr><tr><td>FD</td><td>7.392</td><td>0.859</td><td>8.398</td><td>590.388</td><td>578.604</td><td>-284.302</td><td>0.91</td></tr></tbody></table>

### Land use effect on SOC stock changes

* No significant change of SOC stocks between campaigns by either ESM or FD in croplands (Table 2).

* Significant decrease of SOC stocks in grasslands by ESM (p<0.05) and by FD (p<0.1; table 2).

<table><caption>Table 2. Mean SOC stock change estimated by ESM and FD in croplands and grasslands.</caption><thead><tr><th>Land use</th><th>Approach</th><th>p_val</th><th>Mean difference<br>Mg ha<sup>-1</sup></th><th>se</th><th>n</th></tr></thead><tbody><tr><td>Croplands</td><td>ESM</td><td>0.4238</td><td>-0.1484</td><td>0.7696</td><td>55</td></tr><tr><td>Croplands</td><td>FD</td><td>0.4172</td><td>-0.2146</td><td>1.0224</td><td>55</td></tr><tr><td>Grasslands</td><td>ESM</td><td><strong>0.0440</strong></td><td>-3.8267</td><td>2.1562</td><td>25</td></tr><tr><td>Grasslands</td><td>FD</td><td><strong>0.0611</strong></td><td>-3.9521</td><td>2.4717</td><td>25</td></tr></tbody></table>

* SOC loss rate in grasslands was **surprisingly large** (0.39 Mg ha⁻¹ yr⁻¹) based on both approaches (Table 3).

<table><caption>Table 3. Mean annual change of SOC stocks in croplands and grasslands estimated by ESM and FD.</caption><thead><tr><th>Land use</th><th>Approach</th><th>p_val</th><th>Rate<br>Mg ha<sup>-1</sup> yr<sup>-1</sup></th><th>se</th><th>n</th></tr></thead><tbody><tr><td>Croplands</td><td>ESM</td><td>0.3163</td><td>-0.0372</td><td>0.0775</td><td>55</td></tr><tr><td>Croplands</td><td>FD</td><td>0.3324</td><td>-0.0435</td><td>0.0999</td><td>55</td></tr><tr><td>Grasslands</td><td>ESM</td><td><strong>0.0377</strong></td><td><strong>-0.3911</strong></td><td>0.2108</td><td>25</td></tr><tr><td>Grasslands</td><td>FD</td><td><strong>0.0550</strong></td><td><strong>-0.3908</strong></td><td>0.2358</td><td>25</td></tr></tbody></table>

## Discussion

* The correspondence of SOC content between RMQS 1 and RMQS 2 suggests that the composite sampling accounts well for the spatial variability in the sampling area.

* Good correspondence of CF between campaigns. By choosing only the sites where the ring was used we selected sites with low CF content and presumably with low CF uncertainty.

* It is challenging to know whether the changes of BD between campaigns are linked to land management practices or to the spatial variability between the different soil pits.

* ESM approach is promising for the future RMQS data.

* Further work is needed to determine if ESM is valid when other BD and CF methods are used in national soil monitoring networks. Particularly, the excavation method that is adapted for soils with large CF content.

* Stock change in grasslands is high and unexpected and remains to be confirmed by further measurements.

## References

* Jolivet, Claudy C., Jose-Luis Almeida Falcon, Philippe Berche, Line Boulonne, Marie Fontaine, Laëtitia Gouny, Sébastien Lehmann, et al. 2018. *Manuel du Réseau de Mesures de la Qualité des Sols (RMQS)*. https://hal.inrae.fr/hal-02791718.

* Wendt, J.W., Hauser, S., 2013. An equivalent soil mass procedure for monitoring soil organic carbon in multiple soil layers. Eur. J. Soil Sci. 64, 58–65. https://doi.org/10.1111/ejss.12002
# Assessing carbon stock changes in French top soils in croplands and grasslands: comparison of fixed depth and equivalent soil mass.

<figure><img src="image_2.png" /></figure>

INRAO
science for people, life & earth

Munera-Echeverri JL¹, Martin M¹, Boulonne L¹, Saby N¹, Arrouays D¹.

¹INRAE, InfoSol, 45075, Orléans, France

## Introduction

* We use data from the first (2000-2009) and second (2016-2027) campaign of the French soil quality monitoring network (RMQS) to compare soil organic carbon (SOC) stock changes based on equivalent soil mass (ESM) and fixed-depth (FD) in top soils (30 cm depth) in croplands and grasslands.

## Materials and methods

### Soil sampling

* Sites were selected based on the availability of data of the second campaign, and where the soil physical parameters were determined by the cylinder method in both campaigns.

* Composite soil sample for carbon analysis were taken from a 400 m² systematic unaligned grid every 4 m (Figure 1A).

* Soil pit adjacent to the grid. Three cylinders (500 cm³) were used estimate bulk density (BD) and coarse fragments (CF) at 0-30cm (Figure 2 B). Time between campaigns: 7-16 years.

<figure><img src="image_3.png" /><figcaption>Figure 1. A) Composite sampling and adjacent pits. B) Soil pit for bulk density and coarse fragments. From Jolivet et al. 2018.</figcaption></figure>

### Stocks and equivalent soil mass calculation

* SOC stock FD (Mg ha⁻¹) = BD * depth * SOC conc * (1-CF/100) / 10

<figure><img src="image_4.png" /><figcaption>Figure 2. Principle behind the evaluation of SOC stock changes based on equivalent soil mass and fixed depth. Taken from Wendt & Hauser 2013.</figcaption></figure>

### Statistical analyses

* Linear mixed model fit by residual maximum likelihood (REML)

* Student test corrected for spatial autocorrelation (Moran Index)

## Results

### Data inspection

* Sites distributed in a large proportion of France (Figure 3 A).

* Good correspondence of SOC content and CF between campaigns, and less good for BD (Figure 3 B,C, and D).

<figure><img src="image_5.png" /><figcaption>Figure 3. A) Spatial distribution of the sites. B) Soil organic carbon content, C) coarse fragments, and D) bulk density of RMQS 2 as a function of the values of RMQS 1 (black lines). Red lines are 1:1.</figcaption></figure>

* ESM slightly improves the prediction of SOC stocks of the second campaign compared to FD (Figure 4 & table 1).

<figure><img src="image_6.png" /><figcaption>Figure 4. SOC stocks of RMQS 2 estimated based on A) ESM and B) FD as function of SOC stocks of RMQS 1 (black lines). Red lines are 1:1.</figcaption></figure>

<table><caption>Table 1. Model comparison of SOC stocks in the RMQS 2 as a function of the stocks in RMQS 1 based on ESM and FD.</caption><thead><tr><th></th><th>Intercept</th><th>Slope</th><th>Res. s.e</th><th>BIC</th><th>AIC</th><th>logLik</th><th>R2</th></tr></thead><tbody><tr><td>ESM</td><td>7.261</td><td>0.863</td><td>6.581</td><td>551.632</td><td>539.849</td><td>-264.924</td><td>0.944</td></tr><tr><td>FD</td><td>7.392</td><td>0.859</td><td>8.398</td><td>590.388</td><td>578.604</td><td>-284.302</td><td>0.91</td></tr></tbody></table>

### Land use effect on SOC stock changes

* No significant change of SOC stocks between campaigns by either ESM or FD in croplands (Table 2).

* Significant decrease of SOC stocks in grasslands by ESM (p<0.05) and by FD (p<0.1; table 2).

<table><caption>Table 2. Mean SOC stock change estimated by ESM and FD in croplands and grasslands.</caption><thead><tr><th>Land use</th><th>Approach</th><th>p_val</th><th>Mean difference<br>Mg ha<sup>-1</sup></th><th>se</th><th>n</th></tr></thead><tbody><tr><td>Croplands</td><td>ESM</td><td>0.4238</td><td>-0.1484</td><td>0.7696</td><td>55</td></tr><tr><td>Croplands</td><td>FD</td><td>0.4172</td><td>-0.2146</td><td>1.0224</td><td>55</td></tr><tr><td>Grasslands</td><td>ESM</td><td><strong>0.0440</strong></td><td>-3.8267</td><td>2.1562</td><td>25</td></tr><tr><td>Grasslands</td><td>FD</td><td><strong>0.0611</strong></td><td>-3.9521</td><td>2.4717</td><td>25</td></tr></tbody></table>

* SOC loss rate in grasslands was **surprisingly large (0.39 Mg ha⁻¹ yr⁻¹)** based on both approaches (Table 3).

<table><caption>Table 3. Mean annual change of SOC stocks in croplands and grasslands estimated by ESM and FD.</caption><thead><tr><th>Land use</th><th>Approach</th><th>p_val</th><th>Rate<br>Mg ha<sup>-1</sup> yr<sup>-1</sup></th><th>se</th><th>n</th></tr></thead><tbody><tr><td>Croplands</td><td>ESM</td><td>0.3163</td><td>-0.0372</td><td>0.0775</td><td>55</td></tr><tr><td>Croplands</td><td>FD</td><td>0.3324</td><td>-0.0435</td><td>0.0999</td><td>55</td></tr><tr><td>Grasslands</td><td>ESM</td><td><strong>0.0377</strong></td><td><strong>-0.3911</strong></td><td>0.2108</td><td>25</td></tr><tr><td>Grasslands</td><td>FD</td><td><strong>0.0550</strong></td><td><strong>-0.3908</strong></td><td>0.2358</td><td>25</td></tr></tbody></table>

## Discussion

* The correspondence of SOC content between RMQS 1 and RMQS 2 suggests that the composite sampling accounts well for the spatial variability in the sampling area.

* Good correspondence of CF between campaigns. By choosing only the sites where the ring was used we selected sites with low CF content and presumably with low CF uncertainty.

* It is challenging to know whether the changes of BD between campaigns are linked to land management practices or to the spatial variability between the different soil pits.

* ESM approach is promising for the future RMQS data.

* Further work is needed to determine if ESM is valid when other BD and CF methods are used in national soil monitoring networks. Particularly, the excavation method that is adapted for soils with large CF content.

* Stock change in grasslands is high and unexpected and remains to be confirmed by further measurements.

## References

* Jolivet, Claudy C., Jose-Luis Almeida Falcon, Philippe Berche, Line Boulonne, Marie Fontaine, Laëtitia Gouny, Sébastien Lehmann, et al. 2018. *Manuel du Réseau de Mesures de la Qualité des Sols (RMQS)*. https://hal.inrae.fr/hal-02791718.

* Wendt, J.W., Hauser, S., 2013. An equivalent soil mass procedure for monitoring soil organic carbon in multiple soil layers. Eur. J. Soil Sci. 64, 58–65. https://doi.org/10.1111/ejss.12002