Quantifying hydrological impacts of compacted sandy subsoils using soil water flow simulations: the importance of vegetation parameterization

Pinza, Jayson Gabriel; Devos Stoffels, Ona-Abeni; Debbaut, Robrecht; Staes, Jan; Vanderborght, Jan; Willems, Patrick; Garré, Sarah

doi:https://doi.org/10.5194/egusphere-2025-1166

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https://doi.org/10.5194/egusphere-2025-1166

Preprints

14 Apr 2025

| 14 Apr 2025

Quantifying hydrological impacts of compacted sandy subsoils using soil water flow simulations: the importance of vegetation parameterization

Jayson Gabriel Pinza, Ona-Abeni Devos Stoffels, Robrecht Debbaut, Jan Staes, Jan Vanderborght, Patrick Willems, and Sarah Garré

Abstract. Numerical models can quantify subsoil compaction’s hydrological impacts, useful to evaluate water management measures for climate change adaptations on compacted subsoils (e.g., augmenting groundwater recharge). Compaction also affects vegetation growth, which, however, is often parameterized using only limited field measurements or relations with other variables. Our study shows that uncertainties in vegetation parameters linked to transpiration (leaf area index [LAI]) and water uptake (root depth distribution) can significantly affect hydrological modeling outcomes. We used the HYDRUS-1D soil water flow model to simulate the soil water balance of experimental grass plots on Belgian Campine Region’s sandy soil. The compacted plot has the compact subsoil at 40–55 cm depths while the non-compacted plot underwent de-compaction. Using two year soil moisture sensor data at two depths, we calibrated and validated our models of these compacted and non-compacted plots under three different vegetation parameterizations, reflecting various canopy and root growth reactions to compaction. We then simulated the water balances under future climate scenarios.

Our experiments reveal that the compacted plots exhibited lower LAI while the non-compacted plots had deeper roots. Considering these vegetations’ reactions in models, our simulations show that compaction will not always reduce deep percolation, compensated by the deep rooted non-compacted case model’s higher evapotranspiration. Therefore, this affected vegetation growth can also further influence the water balance. Hence, hydrological modeling studies on (de-)compaction should dynamically incorporate vegetation growth above- and belowground, of which field evidence is vital.

Received: 12 Mar 2025 – Discussion started: 14 Apr 2025

Competing interests: At least one of the co-authors is a member of the editorial board of SOIL.

Publisher's note: Copernicus Publications remains neutral with regard to jurisdictional claims made in the text, published maps, institutional affiliations, or any other geographical representation in this paper. While Copernicus Publications makes every effort to include appropriate place names, the final responsibility lies with the authors. Views expressed in the text are those of the authors and do not necessarily reflect the views of the publisher.

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Jayson Gabriel Pinza, Ona-Abeni Devos Stoffels, Robrecht Debbaut, Jan Staes, Jan Vanderborght, Patrick Willems, and Sarah Garré

Status: closed

RC1:
'Comment on egusphere-2025-1166', Anonymous Referee #1, 31 May 2025

The authors investigated the impact of vegetation on the simulation of water flow under two soil treatment conditions: non-compaction and compaction. The English is generally correct, and the structure of the manuscript is appropriate for a scientific paper. The study's objectives are clearly stated, and the experimental approach is sound. Hydrus-1D was properly calibrated and validated. The findings are relevant and clearly presented, particularly with regard to the sensitivity of the mechanistic model to crop parameters such as root water uptake and leaf area index (LAI). I enjoyed reading the manuscript. However, there are two minor points that the authors may wish to consider in order to improve this version further:
1/- Figures 1 and 2 and Tables 1 and 2 are not essential and could be omitted. They seem more suitable for a review paper than for the current study.
2/- Please clarify the irrigation method used to apply the water amounts, and explain how these amounts were estimated.

Citation: https://doi.org/10.5194/egusphere-2025-1166-RC1
- AC1: 'Reply on RC1', Jayson Gabriel Pinza, 29 Jul 2025
  
  We thank the reviewer for dedicating time and effort to review our manuscript. We are also grateful for the kind words in our work. The comments helped make our paper more concise.
  
  Please see below for our responses on each comment:
  
  REVIEWER 1 COMMENT 1: /- Figures 1 and 2 and Tables 1 and 2 are not essential and could be omitted. They seem more suitable for a review paper than for the current study.
  
  OUR RESPONSE:
  For Figure 1 and Table 1, we will omit them in the main text and transfer them to the Appendix Section. Reviewer 2 also similarly suggested to omit Figure 1 and Table 1.
  For Figure 2, which involves the graphs of boxplots and time series of meteorological variables and LAI, we will omit everything EXCEPT FOR Figures 2c (time series of P, ET, irrigation, temperature) and 2e (LAI time series). We deem 2c and 2e to be significant in the paper because 2c describes the weather conditions during the experiment period while 2e visualizes the vegetation dynamics throughout the experiment. Moreover, the data from Figures 2c and 2e also served as inputs to our calibrated and validated HYDRUS models.
  For the whole Table 2, we also believe it is significant, and we prefer to retain it. As we want our experiment to be as reproducible as possible for other researchers, showing these soil hydraulic properties will help them know the characteristics of our experimental setups. Moreover, these measurements also indicate the presence of subsoil compaction (i.e., higher bulk density, lower saturated hydraulic conductivity).
  
  REVIEWER 1 COMMENT 2: /- Please clarify the irrigation method used to apply the water amounts, and explain how these amounts were estimated.
  
  OUR RESPONSE:
  We irrigated by hand using regular 10-liter graduated watering cans with sprinkler heads. We used these graduations (1 graduation = 1 L) as guide to estimate the irrigation amounts. By simply dividing the total volume in the watering can/s by the plot area (2 meter x 2 meter), we obtain the irrigation amounts in millimeters.
  In line with this comment, we plan to add the text below in line 170-175:
  
  “Irrigation is performed by sprinkling using 10-liter graduated watering cans.”
  Line 170-175 has the paragraph that begins with "In 2022, we mimicked intense summer rainfall events..."
  
  Citation: https://doi.org/10.5194/egusphere-2025-1166-AC1
RC2:
'Comment on egusphere-2025-1166', Fera Cleophas, 21 Jul 2025
Overall comments
This manuscript presents a timely and well-executed study on the hydrological effects of subsoil compaction and de-compaction in sandy soils, with a focus on how vegetation characteristics influence modeling results. The combination of field experiments and modeling is sound, and the findings offer valuable insights for improving water balance assessments in agricultural settings. The paper is generally well-structured and contributes to an underexplored topic. However, some sections, particularly the Methods and Conclusion, would benefit from clearer organization and improved clarity. Minor language and formatting adjustments are also recommended.
Recommendation:
The authors may consider removing Figure 1 and Table 1 from the main body of the paper, summarizing their key points in a short paragraph within the introduction or moving them to an appendix or supplementary material if deemed necessary for completeness.

The manuscript frequently uses first-person pronouns such as "we" and "our" (e.g., lines 87, 88, 89, 145, 171, 175, 285, 293, 521, 528). While this is acceptable in some journals, I recommend replacing these with more objective constructions (e.g., "this study", "the present work", or "the model was calibrated") to maintain a more formal and academic tone, especially if this aligns with the journal’s style guidelines.

line 504 -505: The phrase “one should not forget” in this sentence introduces a conversational tone that may not align with the formal style expected in scientific writing. It would be more appropriate to rephrase this part of the sentence to maintain objectivity and consistency with the overall academic tone of the manuscript.

Line 550- Please remove the citations from the Conclusion section. This part should focus on synthesizing the study's findings and implications without introducing or referencing external sources. If these citations are important to retain, consider moving them to the Discussion section where prior studies are typically discussed in relation to the current work.

A consistent revision throughout the manuscript will enhance its professionalism and neutrality.
Citation: https://doi.org/10.5194/egusphere-2025-1166-RC2
- AC2: 'Reply on RC2', Jayson Gabriel Pinza, 29 Jul 2025
  
  We thank the reviewer for spending time and effort reviewing our manuscript. The comments helped us smoothen the flow of discussion in our paper and ensure a more formal and objective tone throughout. We also appreciate the kind words in our work.
  
  Please see below for our responses on each comment.
  
  REVIEWER 2 COMMENT 1: The authors may consider removing Figure 1 and Table 1 from the main body of the paper, summarizing their key points in a short paragraph within the introduction or moving them to an appendix or supplementary material if deemed necessary for completeness.
  OUR RESPONSE:
  We will omit Figure 1 and Table 1 in the main text and transfer them to the Appendix. Reviewer 1 also suggested omitting them.
  We believe, however, that their key points are already summarized in lines 50-95 (2nd to 4th paragraphs) of the introduction. Thus, we will not add a separate short summative paragraph anymore.
  
  REVIEWER 2 COMMENT 2: The manuscript frequently uses first-person pronouns such as "we" and "our" (e.g., lines 87, 88, 89, 145, 171, 175, 285, 293, 521, 528). While this is acceptable in some journals, I recommend replacing these with more objective constructions (e.g., "this study", "the present work", or "the model was calibrated") to maintain a more formal and academic tone, especially if this aligns with the journal’s style guidelines.
  OUR RESPONSE:
  We will revise all these lines accordingly by replacing the 1st-person pronouns with more objective constructions as suggested.
  
  REVIEWER 2 COMMENT 3: line 504 -505: The phrase “one should not forget” in this sentence introduces a conversational tone that may not align with the formal style expected in scientific writing. It would be more appropriate to rephrase this part of the sentence to maintain objectivity and consistency with the overall academic tone of the manuscript.
  OUR RESPONSE:
  We will simply omit the clause “one should not forget that” to sound more objective while retaining the idea. Thus, the sentence is revised as follows:
  
  “These insights show that while sandy subsoil compaction directly affects both vegetation growth and water balance, the affected vegetation growth also further influences the water balance.”
  
  REVIEWER 2 COMMENT 4: Line 550- Please remove the citations from the Conclusion section. This part should focus on synthesizing the study's findings and implications without introducing or referencing external sources. If these citations are important to retain, consider moving them to the Discussion section where prior studies are typically discussed in relation to the current work.
  OUR RESPONSE:
  We will transfer the whole paragraph from Conclusion section to the Discussion as last paragraph of the subsection “Implications on Water Management”. With this, we can retain the citations.
  
  Citation: https://doi.org/10.5194/egusphere-2025-1166-AC2

Status: closed

RC1:
'Comment on egusphere-2025-1166', Anonymous Referee #1, 31 May 2025

The authors investigated the impact of vegetation on the simulation of water flow under two soil treatment conditions: non-compaction and compaction. The English is generally correct, and the structure of the manuscript is appropriate for a scientific paper. The study's objectives are clearly stated, and the experimental approach is sound. Hydrus-1D was properly calibrated and validated. The findings are relevant and clearly presented, particularly with regard to the sensitivity of the mechanistic model to crop parameters such as root water uptake and leaf area index (LAI). I enjoyed reading the manuscript. However, there are two minor points that the authors may wish to consider in order to improve this version further:
1/- Figures 1 and 2 and Tables 1 and 2 are not essential and could be omitted. They seem more suitable for a review paper than for the current study.
2/- Please clarify the irrigation method used to apply the water amounts, and explain how these amounts were estimated.

Citation: https://doi.org/10.5194/egusphere-2025-1166-RC1
- AC1: 'Reply on RC1', Jayson Gabriel Pinza, 29 Jul 2025
  
  We thank the reviewer for dedicating time and effort to review our manuscript. We are also grateful for the kind words in our work. The comments helped make our paper more concise.
  
  Please see below for our responses on each comment:
  
  REVIEWER 1 COMMENT 1: /- Figures 1 and 2 and Tables 1 and 2 are not essential and could be omitted. They seem more suitable for a review paper than for the current study.
  
  OUR RESPONSE:
  For Figure 1 and Table 1, we will omit them in the main text and transfer them to the Appendix Section. Reviewer 2 also similarly suggested to omit Figure 1 and Table 1.
  For Figure 2, which involves the graphs of boxplots and time series of meteorological variables and LAI, we will omit everything EXCEPT FOR Figures 2c (time series of P, ET, irrigation, temperature) and 2e (LAI time series). We deem 2c and 2e to be significant in the paper because 2c describes the weather conditions during the experiment period while 2e visualizes the vegetation dynamics throughout the experiment. Moreover, the data from Figures 2c and 2e also served as inputs to our calibrated and validated HYDRUS models.
  For the whole Table 2, we also believe it is significant, and we prefer to retain it. As we want our experiment to be as reproducible as possible for other researchers, showing these soil hydraulic properties will help them know the characteristics of our experimental setups. Moreover, these measurements also indicate the presence of subsoil compaction (i.e., higher bulk density, lower saturated hydraulic conductivity).
  
  REVIEWER 1 COMMENT 2: /- Please clarify the irrigation method used to apply the water amounts, and explain how these amounts were estimated.
  
  OUR RESPONSE:
  We irrigated by hand using regular 10-liter graduated watering cans with sprinkler heads. We used these graduations (1 graduation = 1 L) as guide to estimate the irrigation amounts. By simply dividing the total volume in the watering can/s by the plot area (2 meter x 2 meter), we obtain the irrigation amounts in millimeters.
  In line with this comment, we plan to add the text below in line 170-175:
  
  “Irrigation is performed by sprinkling using 10-liter graduated watering cans.”
  Line 170-175 has the paragraph that begins with "In 2022, we mimicked intense summer rainfall events..."
  
  Citation: https://doi.org/10.5194/egusphere-2025-1166-AC1
RC2:
'Comment on egusphere-2025-1166', Fera Cleophas, 21 Jul 2025
Overall comments
This manuscript presents a timely and well-executed study on the hydrological effects of subsoil compaction and de-compaction in sandy soils, with a focus on how vegetation characteristics influence modeling results. The combination of field experiments and modeling is sound, and the findings offer valuable insights for improving water balance assessments in agricultural settings. The paper is generally well-structured and contributes to an underexplored topic. However, some sections, particularly the Methods and Conclusion, would benefit from clearer organization and improved clarity. Minor language and formatting adjustments are also recommended.
Recommendation:
The authors may consider removing Figure 1 and Table 1 from the main body of the paper, summarizing their key points in a short paragraph within the introduction or moving them to an appendix or supplementary material if deemed necessary for completeness.

The manuscript frequently uses first-person pronouns such as "we" and "our" (e.g., lines 87, 88, 89, 145, 171, 175, 285, 293, 521, 528). While this is acceptable in some journals, I recommend replacing these with more objective constructions (e.g., "this study", "the present work", or "the model was calibrated") to maintain a more formal and academic tone, especially if this aligns with the journal’s style guidelines.

line 504 -505: The phrase “one should not forget” in this sentence introduces a conversational tone that may not align with the formal style expected in scientific writing. It would be more appropriate to rephrase this part of the sentence to maintain objectivity and consistency with the overall academic tone of the manuscript.

Line 550- Please remove the citations from the Conclusion section. This part should focus on synthesizing the study's findings and implications without introducing or referencing external sources. If these citations are important to retain, consider moving them to the Discussion section where prior studies are typically discussed in relation to the current work.

A consistent revision throughout the manuscript will enhance its professionalism and neutrality.
Citation: https://doi.org/10.5194/egusphere-2025-1166-RC2
- AC2: 'Reply on RC2', Jayson Gabriel Pinza, 29 Jul 2025
  
  We thank the reviewer for spending time and effort reviewing our manuscript. The comments helped us smoothen the flow of discussion in our paper and ensure a more formal and objective tone throughout. We also appreciate the kind words in our work.
  
  Please see below for our responses on each comment.
  
  REVIEWER 2 COMMENT 1: The authors may consider removing Figure 1 and Table 1 from the main body of the paper, summarizing their key points in a short paragraph within the introduction or moving them to an appendix or supplementary material if deemed necessary for completeness.
  OUR RESPONSE:
  We will omit Figure 1 and Table 1 in the main text and transfer them to the Appendix. Reviewer 1 also suggested omitting them.
  We believe, however, that their key points are already summarized in lines 50-95 (2nd to 4th paragraphs) of the introduction. Thus, we will not add a separate short summative paragraph anymore.
  
  REVIEWER 2 COMMENT 2: The manuscript frequently uses first-person pronouns such as "we" and "our" (e.g., lines 87, 88, 89, 145, 171, 175, 285, 293, 521, 528). While this is acceptable in some journals, I recommend replacing these with more objective constructions (e.g., "this study", "the present work", or "the model was calibrated") to maintain a more formal and academic tone, especially if this aligns with the journal’s style guidelines.
  OUR RESPONSE:
  We will revise all these lines accordingly by replacing the 1st-person pronouns with more objective constructions as suggested.
  
  REVIEWER 2 COMMENT 3: line 504 -505: The phrase “one should not forget” in this sentence introduces a conversational tone that may not align with the formal style expected in scientific writing. It would be more appropriate to rephrase this part of the sentence to maintain objectivity and consistency with the overall academic tone of the manuscript.
  OUR RESPONSE:
  We will simply omit the clause “one should not forget that” to sound more objective while retaining the idea. Thus, the sentence is revised as follows:
  
  “These insights show that while sandy subsoil compaction directly affects both vegetation growth and water balance, the affected vegetation growth also further influences the water balance.”
  
  REVIEWER 2 COMMENT 4: Line 550- Please remove the citations from the Conclusion section. This part should focus on synthesizing the study's findings and implications without introducing or referencing external sources. If these citations are important to retain, consider moving them to the Discussion section where prior studies are typically discussed in relation to the current work.
  OUR RESPONSE:
  We will transfer the whole paragraph from Conclusion section to the Discussion as last paragraph of the subsection “Implications on Water Management”. With this, we can retain the citations.
  
  Citation: https://doi.org/10.5194/egusphere-2025-1166-AC2

Jayson Gabriel Pinza, Ona-Abeni Devos Stoffels, Robrecht Debbaut, Jan Staes, Jan Vanderborght, Patrick Willems, and Sarah Garré

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Short summary

We can use hydrological models to estimate how water is allocated in soils with compaction. However, compaction can also affect how much plants can grow in the field. Here, we show that when we consider this affected plant growth in our sandy soil compaction model, the resulting water allocation can change a lot. Thus, to get more reliable model results, we should know the plant growth (above and below the ground) in the field and include them in the models.


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