Changes in soil organic and inorganic carbon with elevation in a dry alpine rangeland of the northern Qinghai–Tibet Plateau

Liu, Qinglin; Zhang, Ailin; Li, Xiangyi; Yin, Jinfei; Zhang, Yuxue; Sun, Osbert Jianxin; Jiang, Yong

doi:https://doi.org/10.5194/bg-22-4123-2025

Articles | Volume 22, issue 16

https://doi.org/10.5194/bg-22-4123-2025

© Author(s) 2025. This work is distributed under
the Creative Commons Attribution 4.0 License.

https://doi.org/10.5194/bg-22-4123-2025

© Author(s) 2025. This work is distributed under
the Creative Commons Attribution 4.0 License.

Articles | Volume 22, issue 16

Research article

|

26 Aug 2025

Research article |

| 26 Aug 2025

Changes in soil organic and inorganic carbon with elevation in a dry alpine rangeland of the northern Qinghai–Tibet Plateau

Qinglin Liu, Ailin Zhang, Xiangyi Li, Jinfei Yin, Yuxue Zhang, Osbert Jianxin Sun, and Yong Jiang

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Final revised paper (published on 26 Aug 2025)
Supplement to the final revised paper
Preprint (discussion started on 28 Mar 2025)

Interactive discussion

Status: closed

RC1:
'Comment on egusphere-2025-1269', Anonymous Referee #1, 29 Apr 2025

General comments
The manuscript by Liu et al. investigated the pattern of changes in soil organic carbon and soil inorganic carbon along the 3000-4000 m altitude range in the northern Qinghai-Tibetan Plateau region. In this study, SOCD increased with the elevation of altitude and was attributed to the changes of dominated vegetation cover and the decreasing MAT. SICD displayed a nonlinear change and was influenced by soil C/N ratio and soil water content. The topic of the study is very interesting and they found the divergent responses of soil C component to altitude. However, there still some issues needed to be addressed before its publication. First, it is important for the authors to present scientific questions more clearly based on summarizing previous research, and further improve the logical and English expression of the paper. Second, the figure and table notes in the result section need to be modified according to the format and need to be distinguished from the font in the manuscript. Third, in the discussion section, there is still a problem of logic ambiguity in the change of soil inorganic carbon density. Please re-organize the structure of this section, so as to make the logic of the discussion section more reasonable and clearly. Further, there are many long and complex sentences in the article, please modify wherever needed. I also have some specific comments listed below.
Specific comments:
Line 15 Please describe the experimental design in detail
Line 27 Please add the “ratio” after C/N
Line 32 Don't use abbreviations when writing keywords and try to spell the words in full.
Line 37 The meaning of the sentence is not clear, please revise it.
Line 44: Please revised “whereas” to “Whereas”
Line 52 the driven factors?
Line 53-55 This sentence is long, so please split into two short sentences.
Line 58-63 Again, the description of research progress is also too long. It will be better to raise the knowledge gap in a separate sentence.
Line 70 delete most
Line 71 in the soil C storage
Line 72 Previous studies may have neglected the role of SIC in soil carbon inventory in this region.
Line 73-75 Please delete this repetitive sentence.
Line 75-78 These statement about the altitude changes in vegetation and soil nutrient availability should have appeared earlier in this paragraph.
Line 79 whether or to what extent the altitudinal changes in micro-environments and vegetation would affect SOC and SIC remains unknown.
Line 87-90 The two hypotheses are similar: the relative importance of SOC to SIC decreases with altitude vs. SIC would become more profound at higher altitudes.
Line 115 The description of the methods that the experiment was conducted should be further addressed.
Line 126 The soil was collected from 0-30 cm, which was different from 0-20 cm in other literatures. Please explain in the materials and methods and explain why this soil layer is used.
Line 136 The measuring method of SIC is unclear. Is it a calculated value by subtracting SOC from TC or a measured value?
Fig. 2b There were two regression lines, but only one R2 and P values was reported?
Line 198 In Table 1 and Figs 3, 4, the listed variables mismatched, please revise them in the result.
Line 235: showed
Line 236-238: Further, soil organic C pool linearly increased, while soil inorganic C pool appears to be nonlinear along the altitudinal gradient.
Line 246 Unexpectedly, this study found the negative correlation between soil organic C pool and aboveground biomass density. This could be explained by…
Line 258 showed
Line 263, 264 delete “effect”
Line 267-271 Please make a summarized conclusion about how vegetation abundance and climate together affect SOC here.
Line 278 Under this condition, plants may grow faster…
Line 280-282 Please move this main result to L. 274, which could support the role of soil N content in accumulating SOC.
Line 288 could be attributed to alluvial deposit…
Line 296 soil inorganic C pool
Line 297-298 This concluded sentence is a bit contradictory with the previous sentence.
Line 305 on the one hand
Line 311-313 Please modify this sentence more clearly

Citation: https://doi.org/10.5194/egusphere-2025-1269-RC1
- AC1: 'Reply on RC1', Ailin Zhang, 08 May 2025
  
  Reviewer #1:
  Thank you very much for the reviewers' suggestions. We have made the following modifications to the questions raised by the reviewers:
  The manuscript by Liu et al. investigated the pattern of changes in soil organic carbon and soil inorganic carbon along the 3000-4000 m altitude range in the northern Qinghai-Tibetan Plateau region. In this study, SOCD increased with the elevation of altitude and was attributed to the changes of dominated vegetation cover and the decreasing MAT. SICD displayed a nonlinear change and was influenced by soil C/N ratio and soil water content. The topic of the study is very interesting and they found the divergent responses of soil C component to altitude. However, there still some issues needed to be addressed before its publication. First, it is important for the authors to present scientific questions more clearly based on summarizing previous research, and further improve the logical and English expression of the paper. Second, the figure and table notes in the result section need to be modified according to the format and need to be distinguished from the font in the manuscript. Third, in the discussion section, there is still a problem of logic ambiguity in the change of soil inorganic carbon density. Please re-organize the structure of this section, so as to make the logic of the discussion section more reasonable and clearly. Further, there are many long and complex sentences in the article, please modify wherever needed. I also have some specific comments listed below.
  Response: Based on the reviewers' comments, we further clarified the assumptions, corrected the chart errors, and reorganized the analysis of SIC. The specific modification contents can be found in the main text of the article and specific comments.
  Specific comments:
  Line 15 Please describe the experimental design in detail
  Response: In the abstract, we have added the description of the experimental design. “To address this uncertainty, we uniformly selected seven points on the vertical gradient at an altitude of 3,000-4,000 meters in the northern part of the Qinghai-Tibet Plateau to analyze the changing trends of organic carbon (SOC) and inorganic carbon (SIC) in the surface soil.”
  Line 27 Please add the “ratio” after C/N
  Response: Thanks very much to the suggestions of the reviewers, we have revised the sentence.
  Line 32 Don't use abbreviations when writing keywords and try to spell the words in full.
  Response: Thanks very much to the suggestions of the reviewers, we have revised the keywords.
  Line 37 The meaning of the sentence is not clear, please revise it.
  Response: We modify this sentence to “However, despite extensive studies on soil carbon pools in the past, there is still great uncertainty regarding the response of soil C pools to global climate change’.
  Line 44: Please revised “whereas” to “Whereas”
  Response: Thanks very much to the suggestions of the reviewers, we have revised the sentence.
  Line 52 the driven factors?
  Response: Based on the reviewers' opinions, we added specific influencing factors such as climate and vegetation. For specific modifications, please refer to line 52-54.
  Line 53-55 This sentence is long, so please split into two short sentences.
  Response: We modify this sentence to “The Qinghai-Tibet Plateau rises sharply in the altitude gradient, and the ecosystem types have the characteristics of spatial differentiation. Among different ecological types, there are significant differences in climate, vegetation and soil characteristics”.
  Line 58-63 Again, the description of research progress is also too long. It will be better to raise the knowledge gap in a separate sentence.
  Response: According to the reviewers' comments, we modify this sentence to “ However, most studies in this region have mainly focused on the vegetation or soil change patterns of permafrost and meadow ecosystems (Wang et al., 2023a; Chen et al., 2017; Cai et al., 2025. The variation patterns of vegetation and soil carbon pools in alpine meadow ecosystems in arid areas have been largely ignored”.
  Line 70 delete most
  Response: Thanks very much to the suggestions of the reviewers, we have revised the sentence.
  Line 71 in the soil C storage
  Response: Thanks very much to the suggestions of the reviewers, we have revised the sentence.
  Line 72 Previous studies may have neglected the role of SIC in soil carbon inventory in this region.
  Response: Thanks very much to the suggestions of the reviewers, we added this sentence.
  Line 73-75 Please delete this repetitive sentence.
  Response: Thanks very much to the suggestions of the reviewers, we have revised the sentence.
  Line 75-78 These statement about the altitude changes in vegetation and soil nutrient availability should have appeared earlier in this paragraph.
  Response: We placed the description of the changes in vegetation and nutrients on the altitude gradient in paragraphs line 58-62.
  Line 79 whether or to what extent the altitudinal changes in micro-environments and vegetation would affect SOC and SIC remains unknown.
  Response: Thanks very much to the suggestions of the reviewers, we have revised the sentence.
  Line 87-90 The two hypotheses are similar: the relative importance of SOC to SIC decreases with altitude vs. SIC would become more profound at higher altitudes.
  Response: According to the reviewers' comments, we modified the hypothesis as “(1) With the increase of altitude, the decrease of temperature and the increase of vegetation, the content of soil organic carbon increases; (2) With the increase of altitude, the drought limitation is alleviated and the inorganic carbon content in the soil decreases; (3) With the increase of altitude, the proportion of organic carbon in the soil carbon pool increases, while the proportion of inorganic carbon decreases.”
  Line 115 The description of the methods that the experiment was conducted should be further addressed.
  Response: Thanks very much to the suggestions of the reviewers, we have revised the methods in line 118-121.
  Line 126 The soil was collected from 0-30 cm, which was different from 0-20 cm in other literatures. Please explain in the materials and methods and explain why this soil layer is used.
  Response: This is mainly because in this study area, there are more vegetation such as dwarf shrubs, and the root systems are mostly distributed in the range of 0-30cm. Therefore, we chose a soil layer of 0-30cm.
  Line 136 The measuring method of SIC is unclear. Is it a calculated value by subtracting SOC from TC or a measured value?
  Response: The content of SIC was directly determined by neutralization titration.
  Fig. 2b There were two regression lines, but only one R2 and P values was reported?
  Line 198 In Table 1 and Figs 3, 4, the listed variables mismatched, please revise them in the result.
  Response: We have corrected the errors in the chart. For the specific correction content, please refer to the chart in the main text.
  Line 235: showed
  Response: Thanks very much to the suggestions of the reviewers, we have revised the sentence.
  Line 236-238: Further, soil organic C pool linearly increased, while soil inorganic C pool appears to be nonlinear along the altitudinal gradient.
  Response: Thanks very much to the suggestions of the reviewers, we have added the sentence in line 246-247.
  Line 246 Unexpectedly, this study found the negative correlation between soil organic C pool and aboveground biomass density. This could be explained by…
  Response: Thanks very much to the suggestions of the reviewers, we have added the sentence in line 255-257.
  Line 258 showed
  Response: Thanks very much to the suggestions of the reviewers, we have revised the sentence.
  Line 263, 264 delete “effect”
  Response: Thanks very much to the suggestions of the reviewers, we have revised the sentence.
  Line 267-271 Please make a summarized conclusion about how vegetation abundance and climate together affect SOC here.
  Response: According to the research content, a summary of the impact on SOC has been added at the end of this paragraph. “Therefore, with the increase of the altitude gradient and the decrease of temperature, the vegetation type gradually changes from desert to grassland, the soil carbon input increases, the mineralization rate decreases, and the SOC content increases.”
  Line 278 Under this condition, plants may grow faster…
  Response: Thanks very much to the suggestions of the reviewers, we have added the sentence in line 291.
  Line 280-282 Please move this main result to L. 274, which could support the role of soil N content in accumulating SOC.
  Response: Thanks very much to the suggestions of the reviewers, we have revised the sentence.
  Line 288 could be attributed to alluvial deposit…
  Response: Response: Thanks very much to the suggestions of the reviewers, we have revised the sentence in line 300-303.
  Line 296 soil inorganic C pool
  Response: Thanks very much to the suggestions of the reviewers, we have revised the sentence.
  Line 297-298 This concluded sentence is a bit contradictory with the previous sentence.
  Response:The sentence structure description is incorrect. We will modify the high altitude area to the low altitude area.
  Line 305 on the one hand
  Response: Thanks very much to the suggestions of the reviewers, we have revised the sentence.
  Line 311-313 Please modify this sentence more clearly
  Response: Thanks very much to the suggestions of the reviewers, we have revised the sentence as “Our research results show that in the dry, high and cold plateau area of the Qinghai-Tibet Plateau, organic carbon increases linearly with the increase of altitude, while silicon carbide first increases and then decreases with the increase of altitude. ”
  
  Citation: https://doi.org/10.5194/egusphere-2025-1269-AC1
RC2:
'Comment on egusphere-2025-1269', Anonymous Referee #2, 29 Apr 2025
General comments
This manuscript investigates the altitudinal patterns of soil organic carbon (SOC) and inorganic carbon (SIC) in an arid alpine grassland ecosystem in the northern Qinghai-Tibetan Plateau. The study addresses a relevant and underexplored topic and contributes to our understanding of carbon pool dynamics in fragile, water- and temperature-constrained ecosystems. The finding that SOC increases with altitude while SIC shows a non-linear pattern is interesting and provides valuable contrast to previous studies in humid alpine zones. However, several issues related to English expression, logical structure, data analysis (particularly SEM), and the discussion of SIC need to be addressed before publication.

Specific comments:
The manuscript requires moderate editing for grammar and clarity. Some sentences are overly long or awkward (e.g., lines 233–235). Consider professional language polishing.

The current version does not adequately explain the broader research background or the regional climate-vegetation features of the study area. Suggest briefly stating why arid alpine grasslands are important.

The description of climatic and vegetation features of the study area is insufficient in the introduction. Add 1–2 sentences summarizing key traits of arid alpine grasslands.

Hypotheses lack specificity – In the introduction, the hypothesis should be expanded to state expected relationships between environmental, vegetation, and soil variables and SOC/SIC.

line 94-95, 91°18'E, 36°N - 37°49'N, Punctuation error.

Line 105 – Figure S1 is cited but not provided.

The description of the initial SEM model is missing. Please add information on model structure, variable selection rationale, and key fit indices (e.g., χ², RMSEA).

Line 259 – It is stated that MAT and SWC significantly increased SOCD and SICD, but no mechanistic interpretation is provided for SICD.

Discussion on SIC / SIC:

The discussion of SIC is relatively fragmented. Recommend reorganizing it into two parts: (a) Abiotic controls (e.g., parent material, soil water, slope effects); (b) Potential biotic influences (e.g., root respiration, vegetation cover).
Line 303 – “SEM-composite” is unclear. Possibly rephrase as “composite SEM model” or “final SEM structure.”
Citation: https://doi.org/10.5194/egusphere-2025-1269-RC2
- AC2: 'Reply on RC2', Ailin Zhang, 08 May 2025
  
  The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2025/egusphere-2025-1269/egusphere-2025-1269-AC2-supplement.pdf
  
  Citation: https://doi.org/10.5194/egusphere-2025-1269-AC2

Peer review completion

AR: Author's response | RR: Referee report | ED: Editor decision | EF: Editorial file upload

ED: Reconsider after major revisions (12 May 2025) by Sara Vicca

AR by Ailin Zhang on behalf of the Authors (13 May 2025) Author's response Author's tracked changes Manuscript

ED: Reconsider after major revisions (13 May 2025) by Sara Vicca

Dear authors,
Please read the comments I made previously (copied again below) and adjust your manuscript and response letter accordingly.
Best regards
Sara Vicca

Dear authors,

Two reviewers have evaluated your manuscript and were generally positive and I would therefore like to invite you to submit a revised manuscript. The reviewers raised several concerns about the writing and, in particular, about the transparency of your methodology. These points must be fully addressed before the paper can proceed to final acceptance.

In your first reply it was sometimes unclear whether a given reviewer comment would be incorporated into the manuscript. Please prepare (a) a clean, fully revised manuscript, (b) a tracked-changes or annotated version, and (c) a point-by-point response letter that quotes each reviewer remark followed by your action or rebuttal and a page/line reference.

Specifically, I would like to emphasize the need to elaborate the information about the SEM analysis. The current description is too brief to judge or reproduce the analysis. In the Methods, specify the SEM framework and estimator, the sample size and observational unit, the observed variables in each latent/composite block, and the full model-fit statistics together with the a-priori model diagram. In addition, outline the criteria for path pruning, document assumption checks, and provide the R code or model syntax plus the covariance/correlation matrix in the Supplement so that readers can replicate the analysis.

As noted previously, please replace altitude with elevation throughout the text, figures, and tables as well as in the title. As explained previously, 'elevation' is standard in terrestrial ecology and 'altitude' has a slightly different meaning.

Best regards,
Sara Vicca

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AR by Ailin Zhang on behalf of the Authors (19 May 2025) Author's response Author's tracked changes Manuscript

ED: Referee Nomination & Report Request started (20 May 2025) by Sara Vicca

RR by Anonymous Referee #2 (22 May 2025)

RR by Anonymous Referee #1 (30 May 2025)

Suggestions for revision or reasons for rejection

I am satisfied with the revisions by the authors. Further, I went through the revised manuscript with tracked changes and provide some specific edits, especially the hypotheses.
L. 18 soil organic carbon (SOC)
L. 36 carbon (C) stocks
L. 43 soil organic C (SOC) and inorganic C (SIC)
L. 52-54 Under different altitude gradients and vegetation types, the change rules of SOC and SIC pools and the specific driving factors remain unclear.
L. 85 delete “But”
L. 92-94 the content of SOC would increase with the elevation gradient because of the lower temperature and more vegetation
L. 94-95 the content of SIC would decrease with the elevation gradient due to that the drought limitation is gradually alleviated
L. 161 measured
L. 163 measured
L. 190 Elevational variation in …
L. 199 Elevational variation in selective plant community characteristics
L. 210 Elevational variation in …
L. 258 elevational patterns
L. 260 Contrary to previous studies that soil carbon pool of alpine meadows or moist grasslands was mainly composed of organic carbon, this study showed the dominance of soil inorganic carbon in the arid and alpine plateaus.
L. 263-264 please delete this sentence “Our results showed a linear increase in soil organic C pool with rising elevation”, repetition with the next sentence.
L. 297-300 Therefore, with the increase of elevation gradients, the lower temperature and the conversion of vegetation from desert to grassland may cause more C input and less C loss, which in turn increase SOC content.
L. 303 In this study, the direct effect of soil factors on SOC was weak, but could indirectly affect SOC through influencing plant community structure. Soil N level was greater…
L. 312 elevational

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ED: Publish subject to minor revisions (review by editor) (02 Jun 2025) by Sara Vicca

AR by Ailin Zhang on behalf of the Authors (10 Jun 2025) Author's response Author's tracked changes Manuscript

ED: Publish subject to technical corrections (12 Jun 2025) by Sara Vicca

AR by Ailin Zhang on behalf of the Authors (13 Jun 2025) Manuscript

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Short summary

The arid region of the Qinghai–Tibet Plateau is a fragile ecosystem sensitive to environmental change. Changes in the soil carbon pool in this ecosystem will affect the terrestrial carbon cycle. The soil carbon pool in this region is mainly composed of soil inorganic carbon, and the response to environmental changes is clear. At the same time, the impact of environment on vegetation is also an important part of the carbon cycle of terrestrial organisms.