Modeling Soil Organic Carbon Dynamics Across Land Uses in Tropical Andean Ecosystems
, Apolinar Figueroa Casas 1, Diego Jesús Macias Pinto 1 and Rigoberto Rosas-Luis 2,3Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsThe manuscript describes the modelling of soil organic carbon dynamic in a tropical Andean environment. It is suitable for publication in Land. In general it is well written; however, there are some aspects that should be corrected, expanded or explained before considering it for publication.
Title: It is OK.
Keywords: They are related to the research.
Abstract: Please define previously k2.
Introduction: It is straightforward. However, the modelling of soil organic carbon has been extensively studied and reviewed in different environments. Authors should make a better effort to highlight the newness of their proposal.
Material and methods: The area of study, methods, and determination are fully described. However, the observational design should be described better. The selection criteria and the description of the treatments are missing. Also, the methodology of soil sampling (depth, timing, criteria) needs more details.
Some specific comments:
L81. Annual precipitation is preferred instead of monthly intensities.
L89. What are the units in the map?
L231. Figure 3
L237. In spanish
Author Response
The manuscript describes the modelling of soil organic carbon dynamic in a tropical Andean environment. It is suitable for publication in Land. In general it is well written; however, there are some aspects that should be corrected, expanded or explained before considering it for publication.
Response:
We sincerely thank the reviewer for the positive evaluation and encouraging remarks regarding the quality and relevance of our manuscript. We have carefully revised the text, addressing all specific comments by expanding methodological details, improving the clarity of the results and discussion, and providing additional explanations to enhance the transparency and reproducibility of our modelling approach. Detailed responses to each point raised are provided below.
-Title: It is OK.
-Keywords: They are related to the research.
-Abstract: Please define previously k2.
Response:
We thank the reviewer for this helpful comment. The parameter k₂ is now defined in the Abstract as the turnover rate of humified organic matter.
-Introduction: It is straightforward. However, the modelling of soil organic carbon has been extensively studied and reviewed in different environments. Authors should make a better effort to highlight the newness of their proposal.
Response: We thank the reviewer for this valuable suggestion. The Introduction was revised to emphasize the novelty of our model, highlighting that it is specifically calibrated for tropical Andean soils and integrates local edaphic, biological, and management variables. These additions clarify how our approach differs from traditional SOC models developed for temperate regions.
Material and methods: The area of study, methods, and determination are fully described. However, the observational design should be described better. The selection criteria and the description of the treatments are missing. Also, the methodology of soil sampling (depth, timing, criteria) needs more details.
Response: We thank the reviewer for this helpful observation. Section 2.2 (Sampling design and site selection) was added to clarify the observational design, including the number of plots, selection criteria, and soil sampling protocol (depth, timing, and compositing). Additionally, Section 2.3 now specifies that both carbon inputs (litter and forest floor) and soil respiration were monitored over a full annual cycle to capture seasonal variability. These improvements enhance the methodological transparency and reproducibility of the study.
Some specific comments:
L81. Annual precipitation is preferred instead of monthly intensities.
Response: We thank the reviewer for the suggestion. The description of rainfall in the Study Area section was modified to express precipitation as total annual values instead of monthly averages. Line 96
L89. What are the units in the map?
Response: Coordinates are expressed in UTM (meters), Datum WGS84, Zone 18N. line 103
L231. Figure 3
Response: The figure and its caption have been corrected as requested. Line 264
L237. In spanish
Response: We thank the reviewer for noting this oversight. The subsection title was translated into English as “Soil Carbon Dynamics under Different Land Uses. Line 270
Reviewer 2 Report
Comments and Suggestions for AuthorsThis study aims to establish a dynamic compartmental model based on ODEs to simulate the flow and transformation of soil organic carbon (SOC) among litter, humus, and microbial biomass under different land-use patterns in tropical Andean mountainous regions. The model provides an effective tool for understanding carbon stabilization mechanisms in mountain ecosystems and can guide adaptive soil management to enhance carbon sink functionality. The topic of this article has significant practical relevance, with scientifically rigorous methods and solid data analysis. However, there are still some aspects that could be improved to enhance scientific rigor and readability:
The abstract and main text are in English, but the subsection title in Section 4 "Discussion" is "4.1. Dinámica del carbono..."???
Line 231: "Figure X"? Additionally, "Figure 3" is described in the text, but may be missing or inconsistently numbered in the PDF.
It is recommended to add a scatter plot of simulated vs. observed values (with a 1:1 line) to visually demonstrate the model's performance.
Some abbreviations are not clearly defined upon first appearance (e.g., eqC, HSM, etc.), and "Quant," as a parameter representing external carbon input, is not sufficiently explained in the equations.
The article emphasizes the model's accuracy but does not fully discuss its limitations, particularly the reasons for the large prediction bias in the livestock system (LS), such as unmodeled factors like grazing behavior, trampling, and N deposition.
The precision of values in the tables varies (e.g., SOC is reported to two decimal places, while other variables are given to only one decimal place).
Author Response
Comments and Suggestions for Authors
This study aims to establish a dynamic compartmental model based on ODEs to simulate the flow and transformation of soil organic carbon (SOC) among litter, humus, and microbial biomass under different land-use patterns in tropical Andean mountainous regions. The model provides an effective tool for understanding carbon stabilization mechanisms in mountain ecosystems and can guide adaptive soil management to enhance carbon sink functionality. The topic of this article has significant practical relevance, with scientifically rigorous methods and solid data analysis. However, there are still some aspects that could be improved to enhance scientific rigor and readability:
-The abstract and main text are in English, but the subsection title in Section 4 "Discussion" is "4.1. Dinámica del carbono..."???
Response: We appreciate the reviewer’s observation. The subsection title was corrected to English as “Soil Carbon Dynamics under Different Land Uses.”
-Line 231: "Figure X"? Additionally, "Figure 3" is described in the text, but may be missing or inconsistently numbered in the PDF.
Response: We thank the reviewer for noticing this issue. The figure numbering and cross-references have been corrected to ensure consistency throughout the manuscript and the PDF file. “Figure 3” now appears properly labeled and referenced in the text.
-It is recommended to add a scatter plot of simulated vs. observed values (with a 1:1 line) to visually demonstrate the model's performance.
Response: We appreciate this valuable suggestion. A new figure (Figure 4) showing the relationship between observed and simulated SOC values with a 1:1 line has been added to visually illustrate the model’s performance and complement the statistical indicators (R², RMSE, MAE).
-Some abbreviations are not clearly defined upon first appearance (e.g., eqC, HSM, etc.), and "Quant," as a parameter representing external carbon input, is not sufficiently explained in the equations.
Response: All abbreviations (eqC, HSM, Quant) are now defined upon first appearance in Section 2.4 and used consistently throughout the manuscript.
-The article emphasizes the model's accuracy but does not fully discuss its limitations, particularly the reasons for the large prediction bias in the livestock system (LS), such as unmodeled factors like grazing behavior, trampling, and N deposition.
Response: We appreciate this insightful comment. A new paragraph was added to the Discussion highlighting the model’s limitations in the livestock system (LS). It explains that prediction bias may result from unmodeled processes such as grazing intensity, trampling, and nitrogen deposition, which influence soil compaction, microbial activity, and carbon turnover. These factors are now acknowledged as potential sources of uncertainty and targets for future model improvement.
The precision of values in the tables varies (e.g., SOC is reported to two decimal places, while other variables are given to only one decimal place).
Response: We thank the reviewer for pointing out this inconsistency. The precision of all numerical values presented in Tables 1 to 3 has been standardized to the decimal places. This ensures a uniform format and improves the readability and comparability of the results across different land use systems.
Reviewer 3 Report
Comments and Suggestions for AuthorsThe article's topic, related to organic carbon dynamics, is very current and important.
The abstract is well-written. The introduction itself could be expanded on the topic of carbon dynamics in soils, etc. Subsection 2.2, "Soil physical, chemical, and biological properties," needs improvement. The methodology should be described in detail. What equipment/apparatus was used (brand, model, country of origin). If reagents were used, also what type. Each analysis must include a citation related to the methodology. Regarding literature from 1986, in the future, please use the latest available techniques and methods. This field of soil science is very dynamic. The results section is written correctly. Throughout the entire paper, please format the text, citations, etc. according to the requirements. Please adjust the font size in figures, as it is disproportionately large and looks very unattractive. The discussion section is the section in which the authors compare their research results with those of other scientists on the same topic. This article contains few citations in the discussion section. I feel this is an extension of research findings. Please correct and thoroughly discuss the research findings, especially since research on carbon transformations is among the most popular in this field. The work is an original article, yet it is based on only 27 references. This is clearly insufficient. The conclusions are correct. I recommend a serious revision.
Author Response
Comments and Suggestions for Authors
The article's topic, related to organic carbon dynamics, is very current and important.
Response: We sincerely thank the reviewer for this positive assessment. We appreciate the recognition of the relevance of our study on soil organic carbon dynamics, particularly in tropical Andean ecosystems where understanding carbon stabilization processes is essential for sustainable land management.
The abstract is well-written.
Response: We sincerely thank the reviewer for this positive assessment.
The introduction itself could be expanded on the topic of carbon dynamics in soils, etc.
Response: We appreciate this valuable suggestion. The Introduction section has been expanded to provide a broader conceptual background on soil carbon dynamics, including the mechanisms of carbon stabilization, decomposition, and transfer among organic matter pools. Additional references were incorporated to highlight the influence of land-use change on these processes in tropical Andean environments. This expanded discussion (see lines 65–95 in the revised manuscript) strengthens the contextual and theoretical foundation of the study.
Subsection 2.2, "Soil physical, chemical, and biological properties," needs improvement.
Response: We thank the reviewer for this valuable observation. Subsection 2.2 has been revised mainly to improve clarity, organization, and methodological transparency. A new introductory paragraph was added to describe the sampling design, depth, and field conditions, and the analytical procedures for physical, chemical, and biological properties were reformatted for better readability. While the SOC stock equation remains the same, its explanation and link to model calibration were clarified. These adjustments strengthen the methodological coherence of the section (see lines 115–155 in the revised manuscript).
The methodology should be described in detail. What equipment/apparatus was used (brand, model, country of origin). If reagents were used, also what type. Each analysis must include a citation related to the methodology. Regarding literature from 1986, in the future, please use the latest available techniques and methods. This field of soil science is very dynamic.
Response: The methodology section was revised to include detailed information on equipment (brand, model, origin), reagent specifications, and updated analytical references, ensuring alignment with current soil science standards.
The results section is written correctly. Throughout the entire paper, please format the text, citations, etc. according to the requirements.
Response: The manuscript, including text, citations, references, and equations, was reviewed and formatted in full compliance with Land journal requirements.
Please adjust the font size in figures, as it is disproportionately large and looks very unattractive. The discussion section is the section in which the authors compare their research results with those of other scientists on the same topic.
Response: The font size in all figures was adjusted for consistency and visual balance. The Discussion section was also revised to strengthen the comparison of our findings with previous studies on similar topics.
This article contains few citations in the discussion section. I feel this is an extension of research findings. Please correct and thoroughly discuss the research findings, especially since research on carbon transformations is among the most popular in this field.
Response:
We appreciate this valuable comment. In the revised version, the Discussion (Sections 4.1 and 4.2) was substantially expanded to include recent and relevant literature that contextualizes our findings within current research on soil carbon transformations, microbial dynamics, and management effects in Andean and tropical ecosystems. Several new citations were added to strengthen the interpretation of SOC stabilization mechanisms, grazing impacts, and model limitations. These additions provide a more comprehensive and critical discussion that links our results to recent advances in the field.
The work is an original article, yet it is based on only 27 references. This is clearly insufficient.
Response: Thank you for this observation. In the revised version, we have expanded the reference list by incorporating several recent and relevant studies that strengthen both the theoretical background and the discussion. These additions provide broader scientific support and ensure that the manuscript reflects the current state of research on SOC dynamics and modeling in tropical and Andean ecosystems.
The conclusions are correct.
Response: We appreciate the reviewer’s positive assessment. We are pleased that the conclusions were found to be appropriate and accurately reflect the study’s main findings and implications.
I recommend a serious revision.
Response: We acknowledge the reviewer’s recommendation and have carried out a thorough and detailed revision of the manuscript. All sections, particularly the Discussion and References, were strengthened with updated literature, clearer interpretations, and improved coherence to enhance the overall scientific quality and readability of the paper.
Reviewer 4 Report
Comments and Suggestions for AuthorsThe manuscript describes the modeling of soil organic carbon dynamics across land uses in tropical andean ecosystems.
The text is generally well-written, and the language is fluent.
Some other points are raised below; all answers should be included in the revised text.
- 119: How often did you measure SOC in “forest floor litter”?
- Section 2.2: More details should be added, e.g., how did you measure organic carbon content (C_org)?
- Please, ensure uniform formatting in both sections 2.2 and 2.3, e.g., sampling depth (P = 0.30 m) and parameter D in Eq.1
- Section 2.3: Explain in full detail how did you measure one by one all the parameters appearing in Eq.2.
- Section 2.3: More details regarding the model should be added, e.g.,
- the system of ordinary differential equations together with initial conditions and explanations regarding further processing, so that it could be repeated by researchers.
- The same for calibration and optimization procedures
- Are any Refs needed?
- In what way does this model differ from previously reported ones? Are only the models described in Refs 11 and 12 the most relevant ones?
- Describe the limitations of your model.
Author Response
Comments and Suggestions for Authors
The manuscript describes the modeling of soil organic carbon dynamics across land uses in tropical andean ecosystems.
The text is generally well-written, and the language is fluent.
Some other points are raised below; all answers should be included in the revised text.
- 119: How often did you measure SOC in “forest floor litter”?
Response: The sampling frequency has been clarified in the revised manuscript. Forest floor litter SOC was measured biweekly over one full annual cycle (February 2023–January 2024), as described in Section 2.3.
- Section 2.2: More details should be added, e.g., how did you measure organic carbon content (C_org)?
Response: The method used to determine organic carbon content (C_org) has been clarified in Section 2.3. It was measured by dry combustion using an NC 1500 Carlo Erba elemental analyzer (Carlo Erba, Italy)
- Please, ensure uniform formatting in both sections 2.2 and 2.3, e.g., sampling depth (P = 0.30 m) and parameter D in Eq.1
Response: The formatting between Sections 2.2 and 2.3 has been standardized. The sampling depth (P = 0.3 m) and the parameter D in Equation 1 are now presented consistently throughout the manuscript.
- Section 2.3: Explain in full detail how did you measure one by one all the parameters appearing in Eq.2.
Response: The section has been expanded to describe in full detail how each parameter in Eq. 2 was obtained. External carbon inputs (Quant) were directly measured from litterfall and forest-floor litter data, while the remaining parameters (K₁, Fₕ, Fᵣ, Assimilation₂, Kd, K₂) were empirically calibrated and constrained using observed field data on soil respiration, microbial biomass, and SOC values. This addition provides a complete explanation of the measurement and estimation procedures for all model parameters.
- Section 2.3: More details regarding the model should be added, e.g.,
- the system of ordinary differential equations together with initial conditions and explanations regarding further processing, so that it could be repeated by researchers.
- The same for calibration and optimization procedures
- Are any Refs needed?
Response:
The model section was expanded to include the full system of ordinary differential equations (Eqs. 2–4), initial conditions, and a detailed description of calibration and optimization procedures. Additional methodological references were added (Soetaert et al., 2010; Wieder et al., 2014; Campbell & Paustian, 2015) to ensure reproducibility.
- In what way does this model differ from previously reported ones? Are only the models described in Refs 11 and 12 the most relevant ones?
Response:
The Introduction section was expanded to highlight how the proposed model differs from previously reported ones. Unlike global SOC models such as RothC, CENTURY, DNDC, or DayCent, which are parameterized mainly for temperate or agricultural systems, our model explicitly integrates field-based edaphic, biological, and management variables calibrated for Andean soils. It also incorporates the humified carbon rate (k₂) as an indicator of long-term stability, enabling a more realistic representation of carbon dynamics in tropical mountain ecosystems. Additional references were considered to contextualize its relevance beyond those cited in Refs. 11 and 12.
- Describe the limitations of your model.
Response: A new paragraph was added at the end of the Discussion (Lines 580–590) describing the model’s main limitations. It acknowledges that grazing, trampling, and nutrient deposition introduce variability not captured by the current structure and that assumptions of constant microbial efficiency and stable conditions may limit short-term simulations. Future improvements include integrating microbial dynamics and spatially explicit carbon fluxes.
Round 2
Reviewer 1 Report
Comments and Suggestions for AuthorsThe manuscript has been improved following the reviewer's suggestions. I do not have further comments; I think that the manuscript can be accepted for publication.
Reviewer 3 Report
Comments and Suggestions for AuthorsI accept the corrections
Reviewer 4 Report
Comments and Suggestions for AuthorsNo comments
