Review Reports

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

Comments and Suggestions for Authors

The manuscript compares soil carbon fractions and fertility attributes among degraded, forest, and restoration areas in four desertification hotspots in northeastern Brazil. The regional comparison provides potentially useful baseline information, and the discussion appropriately acknowledges substantial edaphic heterogeneity. However, several aspects of the sampling structure, analytical consistency, and interpretation would benefit from further clarification.

 

Major comments:

1. Section 2.1 states that three plots were established within each land-use condition, whereas Section 2.5 and all figure captions report four replicates per combination. Please reconcile this discrepancy and specify exactly what each replicate represents. Report the number of independent sites, plots, soil sampling points, composite samples, and laboratory replicates for each hotspot × land-use combination. Explain how samples were collected within the central sampling area, whether they were composited, and whether any samples were pooled across plots.

Please clarify whether the plots were distributed across independently selected areas or located within a single area for each land-use category. The analysis should account for any nested sampling structure, and limitations arising from a single area per land-use category should be acknowledged.

 

2. The restoration ages, practices, vegetation composition, and previous management are insufficiently described, and the soil classes identified through profile classification are not reported. Please provide a site-characterization table including coordinates, soil classes, landscape positions, vegetation cover, degradation and management history, restoration ages and practices, and known fertilization or liming history.

This information is particularly important in Piauí, where forest and restoration areas differ markedly in texture and pH, limiting their comparability. Please explain the site-selection criteria and how comparability among land-use categories was assessed.

 

3. The study compares current soil conditions across different areas and does not document changes through time. Therefore, claims about recovery trajectories, restoration-induced improvements, or responses preceding TOC recovery should be moderated. Unless additional evidence is available, present the findings as differences associated with the sampled land-use categories rather than demonstrated effects or stages of restoration. Revise the abstract, discussion, and conclusions accordingly.

 

4. Please verify the unit conversions and effective CEC calculations in Figures 4 and 5. K is expressed in cmolc dm^-3, whereas Ca, Mg, and CEC are expressed in mmolc dm^-3. For the forest area in Paraíba, the approximate plotted means are Ca ≈ 12, Mg ≈ 2.3, and K ≈ 8 mmolc dm^-3 after conversion. Their sum is approximately 22 mmolc dm^-3, exceeding the effective CEC of approximately 17-18 mmolc dm^-3 in Figure 5, even before adding Al.

These values are estimated from the figures. Please provide the exact underlying concentrations, including exchangeable Al, and demonstrate how effective CEC was calculated after unit conversion. Correct any calculation or axis-label errors and repeat the relevant analyses if necessary. Use “effective CEC” consistently throughout the manuscript.

 

5. Please clarify the carbon-fractionation procedure in Section 2.4, particularly the NaOH extraction volume and whether extraction was repeated. Indicate any modifications to the cited Benites et al. procedure and provide a reference for the wet-oxidation method.

Based on approximate values read from Figure 3, (FAC + HAC + HC)/TOC is about 49% in the Ceará forest area and 33% in the Paraíba degraded area. Please check these estimates against the underlying data and explain the differences between the summed carbon fractions and TOC, as this would help readers interpret the fractionation results.

 

6. The manuscript reports a significant hotspot × land-use interaction for every variable, but the corresponding ANOVA results are not provided. Please add a summary table reporting the degrees of freedom, test statistics, and p-values for both main effects and their interaction for each variable. Please also briefly describe the statistical model and how the Tukey comparisons shown in the figures were performed. It would be helpful to summarize the results of the normality and variance-homogeneity checks and indicate whether any data transformations were used (Section 2.5).

 

7. In Section 4.2, please discuss carbon stabilization and persistence more cautiously, consistent with the limitations acknowledged in the Introduction. Higher HAC or HC indicates differences in operationally defined carbon fractions, but does not directly demonstrate greater stabilization or persistence. These mechanisms could be presented as possible explanations for the observed patterns.

Please also use “carbon concentrations” when referring to the measured results, as carbon stocks were not calculated.

 

8. In Sections 3.4 and 4.3, it would be helpful to briefly discuss the suitability and limitations of Mehlich-1 across the contrasting soil conditions. Where appropriate, describe the measured values as Mehlich-1-extractable P. Previous fertilization could explain the high P concentrations in some restoration areas, but this should remain a possible explanation unless supported by management records.

 

Minor comments:

1. Please add the Piauí results to the description of effective CEC in Section 3.4, as these represent the largest contrast in Figure 5.

 

2. Please clarify what is meant by “privacy restrictions” in the Data Availability Statement.

 

3. Please address the following minor editorial issues:

• Line 333: Please replace “base cátions” with “base cations.”
• Line 405: Please replace “136% Higher” with “136% higher.”
• Abbreviations table below line 544: Please replace “Exchange capacity” with “Cation exchange capacity” for CEC.
• Lines 688–689: Please remove the empty reference entry 65 and the placeholder reference entry 66.

Comments for author File: Comments.pdf

Author Response

Authors’ Responses to Reviewer 1

We thank the reviewer for the constructive comments. In the table below, we provide a point-by-point response to each comment.

Revier 1 comment	Authors’ response
Major comments: 1.      1. Section 2.1 states that three plots were established within each land-use condition, whereas Section 2.5 and all figure captions report four replicates per combination. Please reconcile this discrepancy and specify exactly what each replicate represents. Report the number of independent sites, plots, soil sampling points, composite samples, and laboratory replicates for each hotspot × land-use combination. Explain how samples were collected within the central sampling area, whether they were composited, and whether any samples were pooled across plots. Please clarify whether the plots were distributed across independently selected areas or located within a single area for each land-use category. The analysis should account for any nested sampling structure, and limitations arising from a single area per land-use category should be acknowledged.	We have revised Section 2.1 (lines 131–141) to clarify the sampling design and reconcile the discrepancy in the number of replicates. Four independent plots (50 × 50 m) were established for each combination of desertification hotspot and land-use condition. Within each plot, a central sampling area (40 × 40 m) was delimited to minimize edge effects. Three soil subsamples were collected at a depth of 0–10 cm and homogenized to obtain one composite sample per plot. No samples were pooled across plots. Thus, each hotspot × land-use combination comprised four plots, 12 soil sampling points, and four independent composite samples, resulting in 48 plots, 144 sampling points, and 48 composite samples across the study. Each composite sample represented one replicate in the statistical analysis. Section 2.5 (lines 186–192) and all figure captions consistently report four replicates per combination (n = 4).
2.      2. The restoration ages, practices, vegetation composition, and previous management are insufficiently described, and the soil classes identified through profile classification are not reported. Please provide a site-characterization table including coordinates, soil classes, landscape positions, vegetation cover, degradation and management history, restoration ages and practices, and known fertilization or liming history. This information is particularly important in Piauí, where forest and restoration areas differ markedly in texture and pH, limiting their comparability. Please explain the site-selection criteria and how comparability among land-use categories was assessed.	We have revised Section 2.1 and added Supplementary Table S1, detailing soil classification, vegetation, degradation history, restoration practices and initiation years, and fertilization history. We have also revised Section 4.1 to discuss soil heterogeneity, particularly the differences in texture and pH in Piauí, and their implications for comparisons among land-use conditions.
3. The study compares current soil conditions across different areas and does not document changes through time. Therefore, claims about recovery trajectories, restoration-induced improvements, or responses preceding TOC recovery should be moderated. Unless additional evidence is available, present the findings as differences associated with the sampled land-use categories rather than demonstrated effects or stages of restoration. Revise the abstract, discussion, and conclusions accordingly.	We have revised the Abstract, Discussion, and Conclusions to avoid causal interpretations and unsupported claims about restoration trajectories. The findings are now presented as differences associated with the sampled land-use conditions rather than demonstrated effects of restoration over time.
4. Please verify the unit conversions and effective CEC calculations in Figures 4 and 5. K is expressed in cmolc dm-3, whereas Ca, Mg, and CEC are expressed in mmolc dm-3. For the forest area in Paraíba, the approximate plotted means are Ca ≈ 12, Mg ≈ 2.3, and K ≈ 8 mmolc dm-3 after conversion. Their sum is approximately 22 mmolc dm-3, exceeding the effective CEC of approximately 17-18 mmolc dm-3 in Figure 5, even before adding Al. These values are estimated from the figures. Please provide the exact underlying concentrations, including exchangeable Al, and demonstrate how effective CEC was calculated after unit conversion. Correct any calculation or axis-label errors and repeat the relevant analyses if necessary. Use “effective CEC” consistently throughout the manuscript.	We have verified the CEC calculations and clarified that the values presented in Figure 5 correspond to potential CEC (T) rather than effective CEC (t). The inconsistency resulted from an incorrect description of the CEC calculation in the manuscript. Potential CEC was calculated as the sum of exchangeable bases (Ca²⁺, Mg²⁺, and K⁺) and potential acidity (H + Al), rather than exchangeable Al³⁺ alone. We have corrected the equation in Section 2.3 and revised the terminology throughout the manuscript, including the Results, Discussion, and Figure 5 caption, to consistently identify the variable as potential CEC. Additionally, we identified minor errors in the units reported for Ca²⁺, Mg²⁺, and CEC. We sincerely apologize for these errors and have corrected the units in the corresponding figures and throughout the manuscript.
5. Please clarify the carbon-fractionation procedure in Section 2.4, particularly the NaOH extraction volume and whether extraction was repeated. Indicate any modifications to the cited Benites et al. procedure and provide a reference for the wet-oxidation method. Based on approximate values read from Figure 3, (FAC + HAC + HC)/TOC is about 49% in the Ceará forest area and 33% in the Paraíba degraded area. Please check these estimates against the underlying data and explain the differences between the summed carbon fractions and TOC, as this would help readers interpret the fractionation results.	We have revised Section 2.4 to clarify the carbon-fractionation procedure, specifying that 1.0 g of soil was extracted with 10 mL of 0.1 mol L⁻¹ NaOH for 24 h. We have also included Yeomans and Bremner as the reference for the wet-oxidation method. Regarding the differences between the sum of the carbon fractions (FAC + HAC + HC) and TOC, these fractions are operationally defined by the chemical fractionation procedure. Their sum may differ from TOC because of methodological differences in carbon extraction, separation, and quantification. We have clarified this distinction in the revised manuscript to facilitate interpretation of the results.
6. The manuscript reports a significant hotspot × land-use interaction for every variable, but the corresponding ANOVA results are not provided. Please add a summary table reporting the degrees of freedom, test statistics, and p-values for both main effects and their interaction for each variable. Please also briefly describe the statistical model and how the Tukey comparisons shown in the figures were performed. It would be helpful to summarize the results of the normality and variance-homogeneity checks and indicate whether any data transformations were used (Section 2.5).	We have included Supplementary Table S2 with the ANOVA results, coefficients of variation, and diagnostic tests necessary for interpreting the findings. Section 2.5 has also been revised to clarify the statistical procedures.
7. In Section 4.2, please discuss carbon stabilization and persistence more cautiously, consistent with the limitations acknowledged in the Introduction. Higher HAC or HC indicates differences in operationally defined carbon fractions, but does not directly demonstrate greater stabilization or persistence. These mechanisms could be presented as possible explanations for the observed patterns. Please also use “carbon concentrations” when referring to the measured results, as carbon stocks were not calculated.	Section 4.2 has been revised to clarify that differences in operationally defined carbon fractions do not directly demonstrate carbon stabilization or persistence. Potential mechanisms are now discussed cautiously, and the terminology has been standardized to refer to carbon concentrations rather than carbon stocks.
8. In Sections 3.4 and 4.3, it would be helpful to briefly discuss the suitability and limitations of Mehlich-1 across the contrasting soil conditions. Where appropriate, describe the measured values as Mehlich-1-extractable P. Previous fertilization could explain the high P concentrations in some restoration areas, but this should remain a possible explanation unless supported by management records.	Sections 3.4 and 4.3 have been revised to clarify the suitability and limitations of the Mehlich-1 method under contrasting soil conditions. Phosphorus values are now referred to as Mehlich-1-extractable P, and previous fertilization is discussed only as a possible explanation for the higher concentrations observed in some restoration areas.
Minor comments: Please add the Piauí results to the description of effective CEC in Section 3.4, as these represent the largest contrast in Figure 5.   Please clarify what is meant by “privacy restrictions” in the Data Availability Statement.   Please address the following minor editorial issues: Line 333: Please replace “base cátions” with “base cations.” Line 405: Please replace “136% Higher” with “136% higher.” Abbreviations table below line 544: Please replace “Exchange capacity” with “Cation exchange capacity” for CEC. Lines 688–689: Please remove the empty reference entry 65 and the placeholder reference entry 66.	All minor comments have been addressed, and the corresponding corrections have been incorporated into the revised manuscript.

 

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

The authors of the manuscript address a relevant topic concerning soil carbon dynamics and fertility under contrasting land-use conditions in critical desertification zones within Brazil's semi-arid region. The multi-regional approach and the simultaneous assessment of soil carbon fractions and fertility attributes provide potentially valuable information. However, important methodological and interpretive aspects require clarification, particularly regarding experimental replication, site and restoration history, soil heterogeneity across the compared areas, and the causal interpretation of restoration effects. Consequently, I believe the manuscript requires substantial revision before it can be considered for publication.

In the title, the authors use the term “Soil Carbon Pools”; however, the study reports TOC concentrations and humic fractions per unit soil mass, rather than C stocks or pools quantified on an area basis. The authors are advised to reconsider this term or explicitly clarify its usage to avoid it being interpreted as a soil carbon stock.

In the Introduction, the objective is correctly stated as an assessment of the association between land-use categories and their properties; however, the authors subsequently frequently resort to terms suggesting degradation or recovery effects. Given that this is a spatial comparison rather than a temporal monitoring of the same sites, it is recommended to maintain this associative interpretation consistently throughout the manuscript.

Section 2.1 (Materials and Methods) lacks essential information regarding the restoration areas. The age of each restoration, the practices implemented, the initial soil condition, and the management history are not clearly specified. This background information is crucial for determining whether the observed differences can reasonably be attributed to restoration processes. The authors are advised to include this information for each site or, if it is unavailable, to explicitly acknowledge this limitation.

Furthermore, there is a significant inconsistency regarding experimental replication. Section 2.1 states that three 50 × 50 m plots were established for each land-use condition, whereas the statistics section indicates four replicates per combination, and the figures also report n = 4. The authors must clarify what the actual experimental unit was, how many independent samples were obtained for each condition, and how the four replicates used in the ANOVA were generated.

In the statistical analysis, the four states were treated as a factor within a 4 × 3 factorial design. However, each state represents a geographically distinct hotspot, with significant differences in precipitation, degradation types, soils, and edaphic conditions. Therefore, the validity of treating them as comparable levels of a single factor and, in particular, the interpretation of the State × land-use interaction should be more clearly justified. It would be advisable for the authors to explain the implications of this structure for the scope of the inferences that can be drawn.

In the Results and Discussion section, the marked textural differences between areas within the same state represent a significant limitation when attributing chemical differences solely to land use. This is particularly evident in Piauí, where the forest area has predominantly sandy soil, whereas the restoration area exhibits considerably higher silt and clay content. Although the authors acknowledge this heterogeneity, it is advisable to emphasize that these differences can confound the interpretation of TOC, humic fractions, nutrients, and CEC, thereby limiting causal inference regarding the restoration's effect.

In the Discussion regarding humic fractions, some expressions suggest that higher HAC and HC contents necessarily imply greater carbon stabilization or more persistent forms of carbon. However, the authors themselves correctly acknowledge in the Introduction that these fractions are operationally defined by the extraction procedure and do not constitute direct measures of carbon persistence. It is recommended to maintain this conceptual caution in the Discussion as well and to avoid interpreting the increase in humin as direct evidence of C stabilization or persistence.

In the Conclusions, it is stated that the restoration areas showed evidence of the recovery of attributes associated with organic matter. This conclusion should be tempered, as the study design does not allow for the demonstration of temporal recovery, and there are significant differences in texture, soil properties, and management history among the areas. The results demonstrate differences in land-use conditions compatible with restoration processes, but they do not allow for unequivocal attribution of these differences to the restoration itself. It is recommended to rephrase the conclusions in terms of associations and to emphasize this limitation.

Author Response

REVIEWER 2 COMMENT: The authors of the manuscript address a relevant topic concerning soil carbon dynamics and fertility under contrasting land-use conditions in critical desertification zones within Brazil's semi-arid region. The multi-regional approach and the simultaneous assessment of soil carbon fractions and fertility attributes provide potentially valuable information. However, important methodological and interpretive aspects require clarification, particularly regarding experimental replication, site and restoration history, soil heterogeneity across the compared areas, and the causal interpretation of restoration effects. Consequently, I believe the manuscript requires substantial revision before it can be considered for publication.

AUTHORS’ RESPONSE: Thank you for your valuable comments and suggestions. All the issues raised have been addressed, and the corresponding revisions and clarifications have been incorporated into the revised manuscript.

 

REVIEWER 2 COMMENT: In the title, the authors use the term “Soil Carbon Pools”; however, the study reports TOC concentrations and humic fractions per unit soil mass, rather than C stocks or pools quantified on an area basis. The authors are advised to reconsider this term or explicitly clarify its usage to avoid it being interpreted as a soil carbon stock.

AUTHORS’ RESPONSE: Thank you for your comment. The requested correction has been made in the revised manuscript.

 

REVIEWER 2 COMMENT: In the Introduction, the objective is correctly stated as an assessment of the association between land-use categories and their properties; however, the authors subsequently frequently resort to terms suggesting degradation or recovery effects. Given that this is a spatial comparison rather than a temporal monitoring of the same sites, it is recommended to maintain this associative interpretation consistently throughout the manuscript.

AUTHORS’ RESPONSE: Thank you for your comment. The Introduction has been revised to emphasize associations rather than causal effects.

 

REVIEWER 2 COMMENT: Section 2.1 (Materials and Methods) lacks essential information regarding the restoration areas. The age of each restoration, the practices implemented, the initial soil condition, and the management history are not clearly specified. This background information is crucial for determining whether the observed differences can reasonably be attributed to restoration processes. The authors are advised to include this information for each site or, if it is unavailable, to explicitly acknowledge this limitation.

AUTHORS’ RESPONSE: Thank you for your comment. The requested information has been added to Section 2.1 and Supplementary Table S1.

 

REVIEWER 2 COMMENT: Furthermore, there is a significant inconsistency regarding experimental replication. Section 2.1 states that three 50 × 50 m plots were established for each land-use condition, whereas the statistics section indicates four replicates per combination, and the figures also report n = 4. The authors must clarify what the actual experimental unit was, how many independent samples were obtained for each condition, and how the four replicates used in the ANOVA were generated.

AUTHORS’ RESPONSE: Thank you for your comment. Section 2.1 has been revised to clarify the experimental units, sampling procedures, and four independent replicates per treatment combination.

 

REVIEWER 2 COMMENT: In the statistical analysis, the four states were treated as a factor within a 4 × 3 factorial design. However, each state represents a geographically distinct hotspot, with significant differences in precipitation, degradation types, soils, and edaphic conditions. Therefore, the validity of treating them as comparable levels of a single factor and, in particular, the interpretation of the State × land-use interaction should be more clearly justified. It would be advisable for the authors to explain the implications of this structure for the scope of the inferences that can be drawn.

AUTHORS’ RESPONSE: Thank you for your comment. Section 2.5 has been revised to justify the factorial structure, clarify the interpretation of the State × land-use interaction, and acknowledge the limitations regarding causal inference and generalization of the results.

 

REVIEWER 2 COMMENT: In the Results and Discussion section, the marked textural differences between areas within the same state represent a significant limitation when attributing chemical differences solely to land use. This is particularly evident in Piauí, where the forest area has predominantly sandy soil, whereas the restoration area exhibits considerably higher silt and clay content. Although the authors acknowledge this heterogeneity, it is advisable to emphasize that these differences can confound the interpretation of TOC, humic fractions, nutrients, and CEC, thereby limiting causal inference regarding the restoration's effect.

AUTHORS’ RESPONSE: Thank you for your comment. The Discussion has been revised to emphasize how textural differences, particularly in Piauí, may confound the interpretation of soil chemical attributes and limit causal inference regarding restoration effects.

 

REVIEWER 2 COMMENT: In the Discussion regarding humic fractions, some expressions suggest that higher HAC and HC contents necessarily imply greater carbon stabilization or more persistent forms of carbon. However, the authors themselves correctly acknowledge in the Introduction that these fractions are operationally defined by the extraction procedure and do not constitute direct measures of carbon persistence. It is recommended to maintain this conceptual caution in the Discussion as well and to avoid interpreting the increase in humin as direct evidence of C stabilization or persistence.

AUTHORS’ RESPONSE: Thank you for your comment. The Discussion has been revised to clarify that humic fractions are operationally defined and that higher HAC and HC contents do not necessarily indicate greater carbon stabilization or persistence.

 

REVIEWER 2 COMMENT: In the Conclusions, it is stated that the restoration areas showed evidence of the recovery of attributes associated with organic matter. This conclusion should be tempered, as the study design does not allow for the demonstration of temporal recovery, and there are significant differences in texture, soil properties, and management history among the areas. The results demonstrate differences in land-use conditions compatible with restoration processes, but they do not allow for unequivocal attribution of these differences to the restoration itself. It is recommended to rephrase the conclusions in terms of associations and to emphasize this limitation.

AUTHORS’ RESPONSE: Thank you for your comment. The Conclusions have been revised to emphasize associations rather than causal effects of restoration and to acknowledge the limitations related to soil heterogeneity, management history, and the absence of temporal data.

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

Most of my previous comments have been addressed. I recommend minor revision to clarify the following points.

1. The TOC coefficient of variation of 55.57% in Table S2 appears inconsistent with Figure 3. Please check the table against the original statistical output and report the results of the normality and variance-homogeneity checks.

2. Please verify the low apparent recovery of carbon fractions relative to TOC against the original records and briefly explain the low values in the manuscript.

3. Please describe how potential acidity (H + Al), used in the revised CEC equation, was measured or estimated.

4. Please correct the coordinates “08°35′82″S” and “36°52′87″W” in Table S1, where the seconds exceed 59.

5. In the Abbreviations table, please replace “Exchange capacity” with “Cation exchange capacity” for CEC.

Author Response

Thank you for your valuable comments and suggestions, which have helped improve the quality of our manuscript. Detailed responses and clarifications are provided in the table below. All requested revisions have been incorporated into the revised manuscript and Supplementary Material, as appropriate.

REVIEWER COMMENT	AUTHORS’ RESPONSES
1. The TOC coefficient of variation of 55.57% in Table S2 appears inconsistent with Figure 3. Please check the table against the original statistical output and report the results of the normality and variance-homogeneity checks.	Thank you for your valuable comment and for identifying this inconsistency. We reexamined the original TOC data and identified a typographical error in the coefficient of variation reported in Table S2. We sincerely apologize for this mistake. The correct residual CV is 6.46%, which is consistent with the standard error bars presented in Figure 3a. We also carefully reviewed the statistical results for all other variables and confirmed that this error was limited to the TOC coefficient of variation. Furthermore, we recalculated the ANOVA and performed the Shapiro-Wilk and Bartlett tests to assess residual normality and homogeneity of variances, respectively. The corresponding results have been incorporated into the Supplementary Table S2. We sincerely appreciate the reviewer's careful assessment, which was essential in identifying and correcting this error before publication.
2. Please verify the low apparent recovery of carbon fractions relative to TOC against the original records and briefly explain the low values in the manuscript.	We carefully reviewed the original analytical records for all variables evaluated in this study and confirmed that the values currently presented in the revised manuscript are correct. We have also expanded Section 4.2 to provide a literature-based explanation for the differences between TOC and the humic carbon fractions. As reported by Dick et al. (2009) and Gerke (2022), the proportion of carbon associated with humic substances relative to TOC varies according to soil type, vegetation, land use and management, climatic conditions, and soil drainage. Furthermore, Oliveira Netto et al. (2024) and Crespo et al. (2024) reported differences in the distribution of fulvic acid, humic acid, and humin carbon across contrasting soil management systems and environmental conditions. These findings provide context for the relatively low sum of humic carbon fractions compared with TOC observed in our study. Accordingly, we have incorporated a new paragraph into Section 4.2 to clarify that the proportion of carbon associated with humic substances is not constant and may vary among soils and land-use conditions. References: Crespo, C.M.G.; Piscoya, V.C.; Moraes, A.S.; França, M.V.; Fernandes, M.M.; Cunha Filho, M.; Cavalcante, N.L.L.; Melo, R.C.P.; Piscoya, T.F.; Piscoya-Roncal, J.; Pereira, L.M.; Gomes Filho, R.R.; Holanda, F.S.R.; Pedrotti, A.; Castro, J.B.; Araújo Filho, R.N. Humic fractions of soil carbon under agroforestry system in altitude swamp Pernambucano. Ciênc. Florest. 2024, 34, e65061.  Dick, D.P.; Novotny, E.H.; Dieckow, J.; Bayer, C. Química da matéria orgânica do solo. In Química e Mineralogia do Solo; Melo, V.F., Alleoni, L.R.F., Eds.; Sociedade Brasileira de Ciência do Solo: Viçosa, Brazil, 2009; Part 2, pp. 1–67. Gerke, J. The central role of soil organic matter in soil fertility and carbon storage. Soil Syst. 2022, 6, 33. Oliveira Netto, A.J.J.G.F.; Fagundes, L.M.; Pinto, L.A.S.R.; Trogello, E.; Pereira, M.G. Cropping and soil management systems effects on soil organic matter fractions in diversified agricultural fields in the Cerrado. Rev. Bras. Cienc. Solo 2024, 48, e0240017.
3. Please describe how potential acidity (H + Al), used in the revised CEC equation, was measured or estimated.	Thank you for your comment. We have revised Section 2.3 (Soil Chemical Analyses) to clarify that potential acidity (H + Al) was extracted using a calcium acetate solution buffered at pH 7.0 and determined by titration with NaOH, using phenolphthalein as an indicator, according to the methodology cited in the manuscript.
4. Please correct the coordinates “08°35′82″S” and “36°52′87″W” in Table S1, where the seconds exceed 59.	Thank you for your comment. The coordinates have been corrected in Supplementary Table S1.
5. In the Abbreviations table, please replace “Exchange capacity” with “Cation exchange capacity” for CEC.	Thank you for your comment. We have corrected the definition of CEC to “Cation exchange capacity” in the Abbreviations table.

Reviewer 2 Report

Comments and Suggestions for Authors

I would like to thank the authors for carefully addressing the comments and suggestions provided during the review process. The revisions have satisfactorily resolved the concerns raised and improved the manuscript's quality. Therefore, I consider the manuscript suitable for acceptance in its present form.

Author Response

Dear Reviewer,

Thank you for your positive feedback and recommendation for acceptance. We sincerely appreciate your valuable comments and suggestions, which have contributed to improving the quality of our manuscript.