the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 04 Oct 2022
Effect of rare earth oxide labeling and sieving methods on aggregate turnover and carbon dynamics
Abstract. Rare earth element oxides (REOs) are effective tracers to investigate soil aggregate dynamics and are also useful to quantify the interaction between C and aggregate dynamics. Although the effect of the REO labeling process on soil aggregates has been considerably investigated, its effect on soil organic carbon remains unknown. The objectives of this study were to (1) determine the effect of the labeling process on soil organic matter, (2) verify the feasibility of using REOs as tracers for investigating Andisols dry and wet sieving aggregate turnover, and (3) analyze the relationship between organic matter and aggregate dynamics during 28 days of incubation. The results showed that the soil organic carbon pool was interfered with by the labeling process, particularly with dissolved organic carbon (DOC), microbial biomass carbon (MBC), and free particulate organic matter (fPOM). Furthermore, the degree of interference was related to the soil sieving method, with the wet sieving process exerting a more significant effect on MBC and fPOM, and the dry sieving process biasing toward DOC. The close 1:1 relationship between measured aggregates and model predictions revealed that REOs are effective tracers for investigating both dry and wet sieving aggregate dynamics in Andisols. Regarding the relationship between organic matter and aggregate dynamics, dry sieving macroaggregate breakdown and restabilization were the largest, shortly appearing in the first incubation week and slowing down thereafter. This trend was also applicable for each dry sieving fraction turnover rate, which correlated significantly with fPOM (0.97, 0.99, and 0.997, P < 0.05). The turnover of wet sieving aggregates also occurred primarily in the first 7 days, but no significant relationship was observed between wet sieving aggregates and soil organic matter dynamics (P > 0.05), which was attributed to numerous wet–dry cycles during the labeling process. The results of the current study indicate that dry sieving aggregates fit better with the quantification of the relationship between aggregates and organic matter dynamics when soil organic matter dynamics were quantified using soil organic carbon pools.
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RC1: 'Comment on egusphere-2022-728', Anonymous Referee #1, 21 Oct 2022
This manuscript from Wang et al. aims at elucidating the effect of rare earth oxide labeling and sieving methods on aggregate turnover and carbon dynamics. To reach their objectives, they conducted labelling and incubation experimentations with dry or wet sieving methods. SOC fractions (DOC, fPOM, MBC and HF) were detected and their relationship with aggregate dynamics were analyzed herein.
Indeed, little researches have reported the effects of labelling and sieving processes on SOC fractions, it is interesting to investigate the discrepancy caused by various methods. But in my view, authors do not provide a clear response to the topic, the research questions are not well stated in the introduction and the findings are not fully discussed in the discussion part. Besides, I doubt the calculation on aggregate turnover rate, which is different from the calculation proposed by De Gryze et al. and Peng et al. For these reasons, I do not recommend the publication of the article in SOIL.
Introduction
The title focused on two factors, namely labelling processes and sieving methods, to aggregate turnover and SOC. Insufficient statements on the importance of these two factors are provided, instead, authors illustrated more the interaction between SOC and soil structure.
Materials and methods
L80 More details on the investigated soil should be provided, such as the initial SOC content, sand/clay/silt content, bulk density etc.
L90-100 Four oxides were used for labelling, but only 3 aggregate fractions were used? So which three oxides you used herein? How to get the recombined soil columns? The soil content and bulk density of these recombined columns? How many soil columns in total? More detailed information is needed.
L120 What do you mean by “regularly”? Every two days?
L125 How much soil is used for dry/wet sieving and SOC fraction detection, respectively?
L175 How to calculate the aggregate turnover?
Results
L190 Since the results and discussion parts are separated herein, no reference should be included in results part.
L200 Please explain the meaning of “unaffected carbon pools”.
L210 It will be easier for readers to follow when 0.25- to 2-, 0.053- to 0.25-, and <0.053-mm are replaced by 0.25-2 mm, 0.053-0.25 mm and <0.053 mm.
L265 I doubt the calculation on aggregate turnover. Take turnover rate of 0.25-2 mm at 7 days as an example, 0.75=(4.58+0.68)/7, it seems that the formation processes are not taken into consideration, which is different from the calculation proposed by De Gryze et al. and Peng et al..
L270 According to Fig.5, the breakdown and formation of dry sieving aggregates occurred not only the first week.
L275 Transformation pathways in Fig. 6 are much smaller than published data. Why? No further discussion are displayed.
L300 There are two “Wet-MBC” in Fig.7a? To present the same SOC fraction, authors used the same color in a, while used the same shape in b, please keep them uniformed.
Discussion
There are lots of repetition of results. No highlights were proposed and discussed here. For section 4.2, lots of publications have proved it, there is no need to discuss again. For section 4.4, the relationship between SOC and aggregate are analyzed, which should be displayed in results rather than discussion part.
Conclusion
It is abstract, not conclusion. The main findings/conclusions, rather than results, are supposed to be included here.
Citation: https://doi.org/10.5194/egusphere-2022-728-RC1 -
AC1: 'Reply on RC1', Wang Yike, 07 Nov 2022
We gratefully thank the editor and reviewer for the time spent making their constructive remarks and helpful suggestion, which has significantly raised the quality of the manuscript and has enabled us to improve the manuscript. Each suggested revision and comment, brought forward by the reviewer was accurately incorporated and considered. Below the reviewer's comments are response point by point and revisions are indicated.
General Comments: This manuscript from Wang et al. aims at elucidating the effect of rare earth oxide labeling and sieving methods on aggregate turnover and carbon dynamics. To reach their objectives, they conducted labelling and incubation experimentations with dry or wet sieving methods. SOC fractions (DOC, fPOM, MBC and HF) were detected and their relationship with aggregate dynamics were analyzed herein.
Indeed, little research have reported the effects of labelling and sieving processes on SOC fractions, it is interesting to investigate the discrepancy caused by various methods. But in my view, the authors do not provide a clear response to the topic, the research questions are not well stated in the introduction and the findings are not fully discussed in the discussion part. Besides, I doubt the calculation on aggregate turnover rate, which is different from the calculation proposed by De Gryze et al. and Peng et al. For these reasons, I do not recommend the publication of the article in SOIL.Response: We greatly appreciate the reviewer's insightful comments. In fact, while processing the data for this manuscript, we found that there was perhaps a hidden innovation, the application of soil organic fractions to quantify soil organic matter, with REE oxides to track the aggregate turnover. In previous studies, Peng et al. (2017) analyzed the organic matter dynamics by adding 13C-labeled glucose to REE oxides labeled soils and determining the 13C content in different aggregate fractions. Subsequently, M. Halder et al. (2022) used eleven organic materials characterized in terms of nutrient stoichiometry, biochemical features and carbon (C) functional groups, to determine which characteristics of organic materials control soil aggregate turnover. However, in the following studies, we found that it would be too expensive to use carbon isotope methods in field experiments or to determine the contribution of organic matter monomers (e.g. galactosamine) for aggregate turnover. This is why a large number of descriptions of the relationship between aggregates and organic carbon have appeared in previous manuscripts.
The main reason for your query about the calculation is that the transformation paths of three aggregate fractions were divided into (1) turnover directly caused by the labeling and sieving processes (at 0 days incubation); (2) turnover caused by soil microorganisms during the incubation process (at 7,14,21,28 days incubation). The excessively low transformation of aggregate turnover pathways is due to the subtraction of transformation before incubation (0 days). We will provide a detailed response to your question about the aggregate turnover calculation in a point-to-point response.
Based on your suggestions, we have restructured the logical framework of the manuscript and will respond to your suggestions in a point-to-point response. In the revised version of the manuscript, we have refined the abstract and main text (especially the Introduction, the Results and the Discussion sections) to make the paper easier to read, the procedure for the calculation of aggregate turnover, which was originally placed in the appendix, has also been collated into 2.5.1 Calculation of soil aggregate turnover in the revised manuscript.
In the Introduction section, we have (1) restructured the framework of the manuscript to make the manuscript more palatable to general readers; (2) outlined the major assumptions briefly; (3) deleted unnecessary description of the relationship between aggregate turnover and soil organic carbon dynamics to make the introduction section more relevant to the topic.
In the Material and method section, we have (1) introduced a more specific description of the Andisols soil samples in 2.1 Soil characteristics; （2）Changed the description of the experiment design in 2.3 Experiment design to make it more consistent with the research topic. (3) Added a flow chart of the recombination process in 2.3.1 Recombination process, to make the recombination process more accessible to the readers; (4) Added 2.5.1Calculation of soil aggregate turnover in the revised manuscript, from the original appendix and added Figure2 The 6 possible transformation pathways of aggregate.
In the Results section, we have (1) modified the structure of the result section according to the revised experiment design, and described the effect of the labeling and sieving process on aggregate turnover and organic carbon fractions, respectively; (2)added transformation aggregates turnover pathways before incubation (0 days) in 3.1.2 Soil aggregate turnover pathways; (3) Added soil organic carbon fraction dynamics of BG treatment during incubation in 3.2.2 The effect of labeling and sieving processes on SOC fractions during incubation process; (4) placed the relationship between aggregate turnover and organic matter dynamics in 3.3 The effects on the quantitative study of the relationship between aggregate turnover and organic matter dynamics.
In the Discussion section, we have reorganized the discussion according to the research topic and your comments. the impact of the labeling and sieving processes on soil aggregate turnover and soil organic carbon fractions were discussed, respectively.
In the Conclusion section, We have (1) identified that labeling and sieving processes could affect aggregate turnover and soil organic carbon fractions; (2) made suggestions for eliminating the disturbances.
Point-to-point response
Comment 1: Introduction, The title focused on two factors, namely labelling processes and sieving methods, to aggregate turnover and SOC. Insufficient statements on the importance of these two factors are provided, instead, authors illustrated more the interaction between SOC and soil structure.
Reply1: We gratefully appreciate for your valuable comment. In the Introduction section, we have (1) deleted unnecessary description of the relationship between aggregate turnover and soil organic carbon dynamics; (2)Restructured the introduction section from labeling and sieving processes on aggregate turnover and organic matter dynamics, to make the introduction section more relevant to the research topic(as shown in supplement).
Comment 2: L80 More details on the investigated soil should be provided, such as the initial SOC content, sand/clay/silt content, bulk density etc.
Reply2: We gratefully appreciate for your valuable comment. We provide the soil properties in 2.1Soil characteristics in the revised manuscript ( 2.1 Soil characteristics, as shown in supplement).
Comment 3: L90-100 Four oxides were used for labelling, but only 3 aggregate fractions were used? So which three oxides you used herein? How to get the recombined soil columns? The soil content and bulk density of these recombined columns? How many soil columns in total? More detailed information is needed.
L120 What do you mean by “regularly”? Every two days?
Reply3: We feel sorry for the inconvenience brought to the reviewer. The comment relates to the labeling process, the recombination process, and the incubation process, therefore we will reply in three parts.
(1) We have placed the labeling process in the 3 Experiment design section, together with the sieving process, recombination process and incubation process. And the labeling process is described in 2.3.1 Labeling process (as shown in the supplement ).
(2)For details of the recombination process are described in 2.3.3 The recombination process and the protocol for recombining aggregates into recombined soils was added, as shown in Figure 1 (as shown in the supplement).
(3)Details of the container for recombined soil and the way of maintaining soil moisture content were described in 2.3.4 Incubation process(as shown in the supplement).
Comment 4:L125 How much soil is used for dry/wet sieving and SOC fraction detection, respectively?
Reply4: Thank you for your rigorous consideration. We would like to respond to this comment in two parts:(1) sieving methods; and (2) soil organic carbon fractions.(1)For the dry/sieving aggregate fraction. Because five treatments were designed in this experiment, we prepared 500g soil samples for each treatment, except for the BG treatment, the treatments involved the labeling process. After labeling process, all labeled soil samples were sieved and recombination, 50 g of sample was sieved at each time (as shown in 2.3.2 Sieving process).
1) Where the descriptions of five treatments are described as: (1) soil without REE oxides labeling and sieving processes (background treatment, BG), (2) soil with dry sieving and REE oxides labeling (REO-labeled and dry sieved treatment, REO-D), (3) soil with wet sieving and REE oxides labeling (REO-labeled and wet sieved treatment, REO-W), (4) soil with dry sieving but without REE oxides labeling (dry sieved treatment, CK-D), and (5) soil with wet sieving but without REE oxides labeling (wet sieved treatment, CK-W).
2) Where the descriptions of the sieving process are described( as shown in supplements)
(2) For the soil organic carbon fractions. Different weights of soil samples were selected according to soil organic carbon fraction determination methods. Where, Total organic carbon(TOC): 0.15–0.20 g; Microbial biomass carbon(MBC):20.00g; Dissolved organic carbon (DOC): 20.00g; free particulate organic carbon (fPOC), occluded particulate organic carbon (oPOC), and a heavy fraction (HF):4.00g. These details about weight have been supplemented in 2.4.2 Analysis of soil organic carbon fractions (as shown in the supplement)
Comment 5:L175 How to calculate the aggregate turnover?
Reply5: We feel sorry for the inconvenience brought to the reviewer. The previous manuscript placed the calculation process in the appendix, which may have caused inconvenience to readers. Therefore, in revised manuscript, we have (1) introduced the calculation procedure in 2.5.1 Calculation of soil aggregate turnover; (2) inserted the schematic diagram of aggregate turnover, to make it easier for readers to understand(as shown in supplements).
Results
Comment 6: L190 Since the results and discussion parts are separated herein, no reference should be included in results part.
Reply6: We gratefully appreciate for your valuable comment. Following your suggestion, the discussion and references in the Results section have been moved to the Discussion section.
Comment 7:L200 Please explain the meaning of “unaffected carbon pools”.
Reply7: Thank you so much for your careful check. In previous manuscripts, as oPOM and HF fractions in Table 1 were less affected by REE oxides addition, labeling, sieving and recombination processes, we have attempted to unify this part of the soil organic carbon fractions into 'unaffected carbon pools' for discussion. In the revised manuscript, we did not add new concepts( like 'unaffected carbon pools') , but described all carbon fractions according to Table3(as shown in the supplement).
Comment 8:L210 It will be easier for readers to follow when 0.25- to 2-, 0.053- to 0.25-, and <0.053-mm are replaced by 0.25-2 mm, 0.053-0.25 mm and <0.053 mm.
Reply 8: We feel sorry for the inconvenience brought to the reviewer. Following your suggestion, we have replaced 0.25- to 2-, 0.053- to 0.25-, and <0.053-mm with 0.25-2 mm, 0.053-0.25 mm and <0.053 mm in revised manuscript.
Comment 9:L265 I doubt the calculation on aggregate turnover. Take turnover rate of 0.25-2 mm at 7 days as an example, 0.75=(4.58+0.68)/7, it seems that the formation processes are not taken into consideration, which is different from the calculation proposed by De Gryze et al. and Peng et al.
L270 According to Fig.5, the breakdown and formation of dry sieving aggregates occurred not only the first week.
L275 Transformation pathways in Fig. 6 are much smaller than published data. Why? No further discussion are displayed.
Reply 9: We totally understand the reviewer’s concern. These three questions are about the transformation of aggregate turnover pathways, so we would like to provide better responses to your comments.
In earlier manuscripts, we were too concerned with the relationship between soil aggregate turnover and soil organic matter, and therefore removed the transformation of aggregate turnover pathways before incubation(0 days) as a disturbance. Actually, to elucidate the influence of the labeling and sieving processes on the aggregates turnover, The transformation paths of three aggregate fractions were divided into (1) turnover directly caused by the labeling and sieving processes (at 0 days incubation); and (2) turnover caused by soil microorganisms during the incubation process (at 7,14,21,28 days incubation). Soil samples obtained from 7, 14, 21 and 28 days of incubation included both the labeling-sieving and recombination processes and the incubation process, whereas samples from 0-day incubation included only the labeling, sieving and recombination processes. Therefore, the turnover pathways of the incubation process are calculated as the difference between the turnover pathways of different incubation days (7, 14, 21, 28days) and the turnover pathways of 0 days of incubation.
In the revised manuscript, we have
(1) Introduced the labeling and sieving process and the incubation process in 2.3 Experimental design describe as:
A series of experiments were conducted in this study. First, The feasibility of REE oxides as tracers to track Andisols aggregate turnover was determined. Then, we divide the effects of REE oxides on Andisols aggregate turnover and organic carbon dynamics into two processes: labeling and sieving processes and incubation process. In the labeling and sieving processes, REE oxides addition, labeling method and sieving method are the main causes of soil organic carbon and aggregate turnover. And in the incubation process variations in soil organic carbon dynamics and aggregate turnover are caused by initial soil organic carbon fractions differences and the soil microbial.
(2) Added Equation(7) in the calculation section as a supplement to the calculation procedures.
Because the Andisols samples were subjected to the labeling process, the sieving process, and the recombination process, and finally to incubation, The labeling, sieving and recombination processes have a destructive effect on aggregates. Soil samples obtained from 7-, 14-, 21- and 28-days incubation included both the labeling-sieving and recombination processes and the incubation process(Ktx), whereas samples from 0-day incubation included only the labeling, sieving and recombination processes (Kt0), then the contribution of the incubation effect to aggregate turnover is calculated as: Kinc= Ktx-Kt0.
(3) Included images and analysis of the transfer pathways between the three aggregate size fractions before incubation(0day) in 3.1.2 Soil aggregate turnover pathways(as shown in supplement).
(4) Compared with Peng et al. (2017) and M. Halder et al. (2022) for the transformation of aggregate turnover pathways and turnover rates in Discussion section 4.1Effects of labeling and sieving processes on Andisols aggregate(as shown in supplement).
Comment 10:L300 There are two “Wet-MBC” in Fig.7a? To present the same SOC fraction, authors used the same color in a, while used the same shape in b, please keep them uniformed.
Reply 10: Thank you so much for your careful check. We apologize for our carelessness. In earlier manuscript, the grey circle represents the "Wet-DOC" instead of "Wet-MBC" in Fig. 7a. In the revised manuscript we have (1) corrected the error in the figure legend; (2) increased the dynamic of the BG treatment organic carbon fractions during incubation(3.2.2 The effect of labeling and sieving processes on SOC fractions during incubation processes, as shown in supplement).
Discussion
Comment 11:There are lots of repetition of results. No highlights were proposed and discussed here. For section 4.2, lots of publications have proved it, there is no need to discuss again. For section 4.4, the relationship between SOC and aggregate are analyzed, which should be displayed in results rather than discussion part.
Reply11:We feel sorry for the inconvenience brought to the reviewer. We have tried too much to illustrate the feasibility of using soil organic carbon fractions and REE oxides to quantify soil organic carbon dynamics and soil aggregate turnover, respectively, and to analyze their relationship. This resulted in the Discussion section being inconsistent with the research topic.
(1)We discussed the effect of labeling and sieving processes on the aggregate turnover from 1)the feasibility of REE oxides as Andisols aggregate tracers; 2) The transformation of aggregate turnover pathways before incubation (0d); 3) The transformation of aggregate turnover pathways during incubation;4) the aggregate turnover rate during incubation(4.1 Effects of labeling and sieving processes on Andisols aggregate,as shown in supplement).
(2) We discussed the effects of the labeling and sieving process on soil organic carbon in terms of 1) the effect of wet sieving on soil organic carbon dynamics; 2) the effect of dry sieving on soil organic carbon dynamics; 3) the feasibility of using soil organic carbon fractions to analyze the relationship between organic matter dynamics and aggregate turnover. (4.2 Effects of REE oxide labeling and sieving processes on soil organic carbon, as shown in supplement)
Conclusion
Comment 12: It is abstract, not conclusion. The main findings/conclusions, rather than results, are supposed to be included here.
Reply12: Thank you for your valuable suggestion.
Conclusions based on the research topic and discussion were obtained from aggregate turnover and soil organic carbon dynamics, respectively. The addition of REE oxides would have no effect on the Andisols aggregate turnover and organic matter dynamics, but the REE oxides labeling and sieving processes would have effects on soil aggregates and soil organic carbon(as shown in supplement).
Acknowledgement
We gratefully thanks for the precious time the reviewer spent making constructive remarks.
Add: We also acknowledge one anonymous reviewer for helpful comments on an earlier draft of our manuscript.
Reference
Based on your suggestions, the Introduction and Discussion sections have been revised a lot, so we have restructured the Reference section. (8 Reference).
We hope you will find our revised manuscript acceptable for publication.
Yours sincerely,
Wang Yike
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AC2: 'Reply on RC1', Wang Yike, 07 Nov 2022
We gratefully thank the editor and reviewer for the time spent making their constructive remarks and helpful suggestion, which has significantly raised the quality of the manuscript and has enabled us to improve the manuscript. Each suggested revision and comment, brought forward by the reviewer was accurately incorporated and considered. Below the reviewer's comments are response point by point and revisions are indicated.
General Comments: This manuscript from Wang et al. aims at elucidating the effect of rare earth oxide labeling and sieving methods on aggregate turnover and carbon dynamics. To reach their objectives, they conducted labelling and incubation experimentations with dry or wet sieving methods. SOC fractions (DOC, fPOM, MBC and HF) were detected and their relationship with aggregate dynamics were analyzed herein.
Indeed, little research have reported the effects of labelling and sieving processes on SOC fractions, it is interesting to investigate the discrepancy caused by various methods. But in my view, the authors do not provide a clear response to the topic, the research questions are not well stated in the introduction and the findings are not fully discussed in the discussion part. Besides, I doubt the calculation on aggregate turnover rate, which is different from the calculation proposed by De Gryze et al. and Peng et al. For these reasons, I do not recommend the publication of the article in SOIL.Response: We greatly appreciate the reviewer's insightful comments. In fact, while processing the data for this manuscript, we found that there was perhaps a hidden innovation, the application of soil organic fractions to quantify soil organic matter, with REE oxides to track the aggregate turnover. In previous studies, Peng et al. (2017) analyzed the organic matter dynamics by adding 13C-labeled glucose to REE oxides labeled soils and determining the 13C content in different aggregate fractions. Subsequently, M. Halder et al. (2022) used eleven organic materials characterized in terms of nutrient stoichiometry, biochemical features and carbon (C) functional groups, to determine which characteristics of organic materials control soil aggregate turnover. However, in the following studies, we found that it would be too expensive to use carbon isotope methods in field experiments or to determine the contribution of organic matter monomers (e.g. galactosamine) for aggregate turnover. This is why a large number of descriptions of the relationship between aggregates and organic carbon have appeared in previous manuscripts.
The main reason for your query about the calculation is that the transformation paths of three aggregate fractions were divided into (1) turnover directly caused by the labeling and sieving processes (at 0 days incubation); (2) turnover caused by soil microorganisms during the incubation process (at 7,14,21,28 days incubation). The excessively low transformation of aggregate turnover pathways is due to the subtraction of transformation before incubation (0 days). We will provide a detailed response to your question about the aggregate turnover calculation in a point-to-point response.
Based on your suggestions, we have restructured the logical framework of the manuscript and will respond to your suggestions in a point-to-point response. In the revised version of the manuscript, we have refined the abstract and main text (especially the Introduction, the Results and the Discussion sections) to make the paper easier to read, the procedure for the calculation of aggregate turnover, which was originally placed in the appendix, has also been collated into 2.5.1 Calculation of soil aggregate turnover in the revised manuscript.
In the Introduction section, we have (1) restructured the framework of the manuscript to make the manuscript more palatable to general readers; (2) outlined the major assumptions briefly; (3) deleted unnecessary description of the relationship between aggregate turnover and soil organic carbon dynamics to make the introduction section more relevant to the topic.
In the Material and method section, we have (1) introduced a more specific description of the Andisols soil samples in 2.1 Soil characteristics; （2）Changed the description of the experiment design in 2.3 Experiment design to make it more consistent with the research topic. (3) Added a flow chart of the recombination process in 2.3.1 Recombination process, to make the recombination process more accessible to the readers; (4) Added 2.5.1Calculation of soil aggregate turnover in the revised manuscript, from the original appendix and added Figure2 The 6 possible transformation pathways of aggregate.
In the Results section, we have (1) modified the structure of the result section according to the revised experiment design, and described the effect of the labeling and sieving process on aggregate turnover and organic carbon fractions, respectively; (2)added transformation aggregates turnover pathways before incubation (0 days) in 3.1.2 Soil aggregate turnover pathways; (3) Added soil organic carbon fraction dynamics of BG treatment during incubation in 3.2.2 The effect of labeling and sieving processes on SOC fractions during incubation process; (4) placed the relationship between aggregate turnover and organic matter dynamics in 3.3 The effects on the quantitative study of the relationship between aggregate turnover and organic matter dynamics.
In the Discussion section, we have reorganized the discussion according to the research topic and your comments. the impact of the labeling and sieving processes on soil aggregate turnover and soil organic carbon fractions were discussed, respectively.
In the Conclusion section, We have (1) identified that labeling and sieving processes could affect aggregate turnover and soil organic carbon fractions; (2) made suggestions for eliminating the disturbances.
Point-to-point response
Comment 1: Introduction, The title focused on two factors, namely labelling processes and sieving methods, to aggregate turnover and SOC. Insufficient statements on the importance of these two factors are provided, instead, authors illustrated more the interaction between SOC and soil structure.
Reply1: We gratefully appreciate for your valuable comment. In the Introduction section, we have (1) deleted unnecessary description of the relationship between aggregate turnover and soil organic carbon dynamics; (2)Restructured the introduction section from labeling and sieving processes on aggregate turnover and organic matter dynamics, to make the introduction section more relevant to the research topic(as shown in supplement).
Comment 2: L80 More details on the investigated soil should be provided, such as the initial SOC content, sand/clay/silt content, bulk density etc.
Reply2: We gratefully appreciate for your valuable comment. We provide the soil properties in 2.1Soil characteristics in the revised manuscript ( 2.1 Soil characteristics, as shown in supplement).
Comment 3: L90-100 Four oxides were used for labelling, but only 3 aggregate fractions were used? So which three oxides you used herein? How to get the recombined soil columns? The soil content and bulk density of these recombined columns? How many soil columns in total? More detailed information is needed.
L120 What do you mean by “regularly”? Every two days?
Reply3: We feel sorry for the inconvenience brought to the reviewer. The comment relates to the labeling process, the recombination process, and the incubation process, therefore we will reply in three parts.
(1) We have placed the labeling process in the 3 Experiment design section, together with the sieving process, recombination process and incubation process. And the labeling process is described in 2.3.1 Labeling process (as shown in the supplement ).
(2)For details of the recombination process are described in 2.3.3 The recombination process and the protocol for recombining aggregates into recombined soils was added, as shown in Figure 1 (as shown in the supplement).
(3)Details of the container for recombined soil and the way of maintaining soil moisture content were described in 2.3.4 Incubation process(as shown in the supplement).
Comment 4:L125 How much soil is used for dry/wet sieving and SOC fraction detection, respectively?
Reply4: Thank you for your rigorous consideration. We would like to respond to this comment in two parts:(1) sieving methods; and (2) soil organic carbon fractions.(1)For the dry/sieving aggregate fraction. Because five treatments were designed in this experiment, we prepared 500g soil samples for each treatment, except for the BG treatment, the treatments involved the labeling process. After labeling process, all labeled soil samples were sieved and recombination, 50 g of sample was sieved at each time (as shown in 2.3.2 Sieving process).
1) Where the descriptions of five treatments are described as: (1) soil without REE oxides labeling and sieving processes (background treatment, BG), (2) soil with dry sieving and REE oxides labeling (REO-labeled and dry sieved treatment, REO-D), (3) soil with wet sieving and REE oxides labeling (REO-labeled and wet sieved treatment, REO-W), (4) soil with dry sieving but without REE oxides labeling (dry sieved treatment, CK-D), and (5) soil with wet sieving but without REE oxides labeling (wet sieved treatment, CK-W).
2) Where the descriptions of the sieving process are described( as shown in supplements)
(2) For the soil organic carbon fractions. Different weights of soil samples were selected according to soil organic carbon fraction determination methods. Where, Total organic carbon(TOC): 0.15–0.20 g; Microbial biomass carbon(MBC):20.00g; Dissolved organic carbon (DOC): 20.00g; free particulate organic carbon (fPOC), occluded particulate organic carbon (oPOC), and a heavy fraction (HF):4.00g. These details about weight have been supplemented in 2.4.2 Analysis of soil organic carbon fractions (as shown in the supplement)
Comment 5:L175 How to calculate the aggregate turnover?
Reply5: We feel sorry for the inconvenience brought to the reviewer. The previous manuscript placed the calculation process in the appendix, which may have caused inconvenience to readers. Therefore, in revised manuscript, we have (1) introduced the calculation procedure in 2.5.1 Calculation of soil aggregate turnover; (2) inserted the schematic diagram of aggregate turnover, to make it easier for readers to understand(as shown in supplements).
Results
Comment 6: L190 Since the results and discussion parts are separated herein, no reference should be included in results part.
Reply6: We gratefully appreciate for your valuable comment. Following your suggestion, the discussion and references in the Results section have been moved to the Discussion section.
Comment 7:L200 Please explain the meaning of “unaffected carbon pools”.
Reply7: Thank you so much for your careful check. In previous manuscripts, as oPOM and HF fractions in Table 1 were less affected by REE oxides addition, labeling, sieving and recombination processes, we have attempted to unify this part of the soil organic carbon fractions into 'unaffected carbon pools' for discussion. In the revised manuscript, we did not add new concepts( like 'unaffected carbon pools') , but described all carbon fractions according to Table3(as shown in the supplement).
Comment 8:L210 It will be easier for readers to follow when 0.25- to 2-, 0.053- to 0.25-, and <0.053-mm are replaced by 0.25-2 mm, 0.053-0.25 mm and <0.053 mm.
Reply 8: We feel sorry for the inconvenience brought to the reviewer. Following your suggestion, we have replaced 0.25- to 2-, 0.053- to 0.25-, and <0.053-mm with 0.25-2 mm, 0.053-0.25 mm and <0.053 mm in revised manuscript.
Comment 9:L265 I doubt the calculation on aggregate turnover. Take turnover rate of 0.25-2 mm at 7 days as an example, 0.75=(4.58+0.68)/7, it seems that the formation processes are not taken into consideration, which is different from the calculation proposed by De Gryze et al. and Peng et al.
L270 According to Fig.5, the breakdown and formation of dry sieving aggregates occurred not only the first week.
L275 Transformation pathways in Fig. 6 are much smaller than published data. Why? No further discussion are displayed.
Reply 9: We totally understand the reviewer’s concern. These three questions are about the transformation of aggregate turnover pathways, so we would like to provide better responses to your comments.
In earlier manuscripts, we were too concerned with the relationship between soil aggregate turnover and soil organic matter, and therefore removed the transformation of aggregate turnover pathways before incubation(0 days) as a disturbance. Actually, to elucidate the influence of the labeling and sieving processes on the aggregates turnover, The transformation paths of three aggregate fractions were divided into (1) turnover directly caused by the labeling and sieving processes (at 0 days incubation); and (2) turnover caused by soil microorganisms during the incubation process (at 7,14,21,28 days incubation). Soil samples obtained from 7, 14, 21 and 28 days of incubation included both the labeling-sieving and recombination processes and the incubation process, whereas samples from 0-day incubation included only the labeling, sieving and recombination processes. Therefore, the turnover pathways of the incubation process are calculated as the difference between the turnover pathways of different incubation days (7, 14, 21, 28days) and the turnover pathways of 0 days of incubation.
In the revised manuscript, we have
(1) Introduced the labeling and sieving process and the incubation process in 2.3 Experimental design describe as:
A series of experiments were conducted in this study. First, The feasibility of REE oxides as tracers to track Andisols aggregate turnover was determined. Then, we divide the effects of REE oxides on Andisols aggregate turnover and organic carbon dynamics into two processes: labeling and sieving processes and incubation process. In the labeling and sieving processes, REE oxides addition, labeling method and sieving method are the main causes of soil organic carbon and aggregate turnover. And in the incubation process variations in soil organic carbon dynamics and aggregate turnover are caused by initial soil organic carbon fractions differences and the soil microbial.
(2) Added Equation(7) in the calculation section as a supplement to the calculation procedures.
Because the Andisols samples were subjected to the labeling process, the sieving process, and the recombination process, and finally to incubation, The labeling, sieving and recombination processes have a destructive effect on aggregates. Soil samples obtained from 7-, 14-, 21- and 28-days incubation included both the labeling-sieving and recombination processes and the incubation process(Ktx), whereas samples from 0-day incubation included only the labeling, sieving and recombination processes (Kt0), then the contribution of the incubation effect to aggregate turnover is calculated as: Kinc= Ktx-Kt0.
(3) Included images and analysis of the transfer pathways between the three aggregate size fractions before incubation(0day) in 3.1.2 Soil aggregate turnover pathways(as shown in supplement).
(4) Compared with Peng et al. (2017) and M. Halder et al. (2022) for the transformation of aggregate turnover pathways and turnover rates in Discussion section 4.1Effects of labeling and sieving processes on Andisols aggregate(as shown in supplement).
Comment 10:L300 There are two “Wet-MBC” in Fig.7a? To present the same SOC fraction, authors used the same color in a, while used the same shape in b, please keep them uniformed.
Reply 10: Thank you so much for your careful check. We apologize for our carelessness. In earlier manuscript, the grey circle represents the "Wet-DOC" instead of "Wet-MBC" in Fig. 7a. In the revised manuscript we have (1) corrected the error in the figure legend; (2) increased the dynamic of the BG treatment organic carbon fractions during incubation(3.2.2 The effect of labeling and sieving processes on SOC fractions during incubation processes, as shown in supplement).
Discussion
Comment 11:There are lots of repetition of results. No highlights were proposed and discussed here. For section 4.2, lots of publications have proved it, there is no need to discuss again. For section 4.4, the relationship between SOC and aggregate are analyzed, which should be displayed in results rather than discussion part.
Reply11:We feel sorry for the inconvenience brought to the reviewer. We have tried too much to illustrate the feasibility of using soil organic carbon fractions and REE oxides to quantify soil organic carbon dynamics and soil aggregate turnover, respectively, and to analyze their relationship. This resulted in the Discussion section being inconsistent with the research topic.
(1)We discussed the effect of labeling and sieving processes on the aggregate turnover from 1)the feasibility of REE oxides as Andisols aggregate tracers; 2) The transformation of aggregate turnover pathways before incubation (0d); 3) The transformation of aggregate turnover pathways during incubation;4) the aggregate turnover rate during incubation(4.1 Effects of labeling and sieving processes on Andisols aggregate,as shown in supplement).
(2) We discussed the effects of the labeling and sieving process on soil organic carbon in terms of 1) the effect of wet sieving on soil organic carbon dynamics; 2) the effect of dry sieving on soil organic carbon dynamics; 3) the feasibility of using soil organic carbon fractions to analyze the relationship between organic matter dynamics and aggregate turnover. (4.2 Effects of REE oxide labeling and sieving processes on soil organic carbon, as shown in supplement)
Conclusion
Comment 12: It is abstract, not conclusion. The main findings/conclusions, rather than results, are supposed to be included here.
Reply12: Thank you for your valuable suggestion.
Conclusions based on the research topic and discussion were obtained from aggregate turnover and soil organic carbon dynamics, respectively. The addition of REE oxides would have no effect on the Andisols aggregate turnover and organic matter dynamics, but the REE oxides labeling and sieving processes would have effects on soil aggregates and soil organic carbon(as shown in supplement).
Acknowledgement
We gratefully thanks for the precious time the reviewer spent making constructive remarks.
Add: We also acknowledge one anonymous reviewer for helpful comments on an earlier draft of our manuscript.
Reference
Based on your suggestions, the Introduction and Discussion sections have been revised a lot, so we have restructured the Reference section. (8 Reference).
We hope you will find our revised manuscript acceptable for publication.
Yours sincerely,
Wang Yike
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AC1: 'Reply on RC1', Wang Yike, 07 Nov 2022
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RC2: 'Comment on egusphere-2022-728', Anonymous Referee #2, 22 Nov 2022
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2022/egusphere-2022-728/egusphere-2022-728-RC2-supplement.pdf
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AC3: 'Reply on RC2', Wang Yike, 03 Dec 2022
Response to reviewers
We gratefully thank the editor and reviewer for the time spent making their constructive remarks and helpful suggestion, which has significantly raised the quality of the manuscript and has enabled us to improve the manuscript. Each suggested revision and comment, brought forward by the reviewer was accurately incorporated and considered. Below the reviewer's comments are response point by point and revisions are indicated.
'Comment on egusphere-2022-728', Anonymous Referee #2, 22 Nov 2022
General Comments: This manuscript by Wang et al. presented an important and interesting study of the effects of REOs labeling process and sieving methods on aggregate turnover and carbon dynamic. Researching soil aggregates and associated biogeochemical processes is a very time-consuming and laborious work, with the complex REOs labeling process makes it to be more difficult. Recently, studies focusing on aggregate turnover show a rising trend, while less researches have reported the role of labelling and sieving processes played in affecting aggregate turnover and soil C dynamics, which may obscure or even magnify the effect of treatments. Dividing the labeling process from the incubation (or other treatments) thus is pivotal for accurately assess the real aggregate turnover dynamics and soil C dynamics. Indeed, the authors found that labeling process and sieving method affect aggregate turnover and soil C fractions (particularly labile C fraction, i.e., DOC, MBC) more intensively than incubation. However, the text has low readability. The logic is very confusing, and the authors seem unable to catch the highlights and key points of the story. Additionally, some key information about the calculations do not show in article. I very appreciate with the work and its significance the authors done. However, I feel a pity that the authors show the story in a not good way. So, I do not recommend the publication of the article in SOIL. The best result is resubmission after major revision.
Response: We greatly appreciate the reviewer's insightful comments. In fact, while processing the data for this manuscript, we found that there was perhaps a hidden innovation, the application of soil organic fractions to quantify soil organic carbon, with REE oxides to track the aggregate turnover. In previous studies, Peng et al. (2017) analyzed the organic carbon dynamics by adding 13C-labeled glucose to REE oxides labeled soils and determining the 13C content in different aggregate fractions. Subsequently, M. Halder et al. (2022) used eleven organic materials characterized in nutrient stoichiometry, biochemical features and carbon (C) functional groups, to determine which characteristics of organic materials control soil aggregate turnover. However, in our following studies, we found that it would be too expensive to use carbon isotope methods in field experiments or to determine the contribution of organic carbon monomers (e.g. galactosamine) for aggregate turnover. This is why some parts focus on the effect of labeling and sieving processes on aggregate and SOM dynamics, and some parts focus on the descriptions of the relationship between aggregates and organic carbon in previous manuscripts, Which resulted in the manuscript's logic seeming pretty confusing and not well readable. Apologies again to the reviewers.
Based on your suggestions, we have restructured the logical framework of the manuscript and will respond to your suggestions in a point-to-point response. In the revised version of the manuscript, we have refined the abstract and main text (especially the Introduction, the Results and the Discussion sections) to make the paper easier to read, the procedure for the calculation of aggregate turnover, which was originally placed in the appendix, has also been collated into 2.5.1 Calculation of soil aggregate turnover in the revised manuscript.
In the Introduction section, we have (1) restructured the framework of the manuscript to make the manuscript more palatable to general readers; (2) outlined the major assumptions briefly; (3) deleted unnecessary description of the relationship between aggregate turnover and soil organic carbon dynamics to make the introduction section more relevant to the topic.
In the Material and method section, we have (1) introduced a more specific description of the Andisols soil samples in 2.1 Soil characteristics; （2）Changed the description of the experiment design in 2.3 Experiment design to make it more consistent with the research topic. (3) Added a flow chart of the recombination process in 2.3.1 Recombination process, to make the recombination process more accessible to the readers; (4) Added 2.5.1Calculation of soil aggregate turnover in the revised manuscript, from the original appendix and added Figure2 The 6 possible transformation pathways of aggregate.
In the Results section, we have (1) modified the structure of the result section according to the revised experiment design, and described the effect of the labeling and sieving process on aggregate turnover and organic carbon fractions, respectively; (2)added transformation aggregates turnover pathways before incubation (0 days) in 3.1.2 Soil aggregate turnover pathways; (3) Added soil organic carbon fraction dynamics of BG treatment during incubation in 3.2.2 The effect of labeling and sieving processes on SOC fractions during incubation process; (4) placed the relationship between aggregate turnover and organic carbon dynamics in 3.3 The effects on the quantitative study of the relationship between aggregate turnover and organic carbon dynamics.
In the Discussion section, we have reorganized the discussion according to the research topic and your comments. the impact of the labeling and sieving processes on soil aggregate turnover and soil organic carbon fractions were discussed, respectively.
In the Conclusion section, We have (1) identified that labeling and sieving processes could affect aggregate turnover and soil organic carbon fractions; (2) made suggestions for eliminating the disturbances.
Point to point response
Comment 1: Introduction, The introduction does not align well with the topic. The article aims to reveal the effects of labeling process and sieving method on aggregate turnover and soil C dynamics. However, in the introduction, related statements are rare, and the authors paid more attention to some unrelated points. For example, the soil types previous REOs studies has been used. Is the soil type (Andisols) very important? I do not think so. In my opinion, the authors should show us the shortage in REOs labeling studies (i.e., overlooks the effects of labeling process and sieving method) and its importance in assessing aggregate turnover dynamic and soil C dynamics, possible effects of labeling process and sieving method on aggregate turnover and soil C dynamics and how do them, and the potential relationships between aggregate turnover and soil C dynamics.
L39-42 why do you mention the concept of “humus”? does your study involve the chemical stability of SOM? the POM and HF you studied are fractioned by physical and density fraction method, not by acid or alkaline or thermal hydrolysis, right? Although they have different functions, they are commonly regarded from a perspective of physical stability/protection.
Reply1: We gratefully appreciate for your valuable comment. In the Introduction section, We have summarized comment1 as follows:
(1)The introduction does not fit the topic;
(2)Whether the soil type (Andisols) is important for the manuscript's results;
(3)Since 'humus' is not mentioned in the manuscript, the introduction to 'humus' should not be included in the introduction.
we have
(1)restructured introduction section from labeling and sieving processes on aggregate turnover and organic carbon dynamics, to make the introduction section more relevant to the research topic;
(2)added the explanation about the importance of soil types;
(3)deleted unnecessary description of the relationship between aggregate turnover and soil organic carbon dynamics;
Materials and methods
Comment 2: more details of the soil properties show be shown, such as SOC, soil texture and etcs.
Reply2: We gratefully appreciate for your valuable comment. We provide more soil properties in 2.1Soil characteristics in the revised manuscript. The soil properties were: bulk density:0.78g cm-3; soil pH: 6.50; total organic carbon (TOC): 53.21 mg g−1, total N: 4.54 mg g−1 , short range order mineral(SRO: allophane + ferrihydrite): 168 mg g−1; Sand (2.0–0.05 mm): 23.92%; Silt (0.05–0.002 mm): 31.02%; Clay (<0.002 mm): 45.06%.
Comment 3: L84-85: “soil sampled by a core at five random locations”. What’s the diameter of soil core? How large the region of soil sampling? Given that soil is highly heterogenous, how representative are the five cores?
Reply3: Thank you for your reminder. The diameter of the soil core is 5cm. The tillage site is a relatively smaller experimental field than normal farmland, the size of the experimental field is 22.5m*14m, and well organized by The National Agriculture and Food Research Organization, Japan. They carefully design and manage their experimental fields to avoid heterogeneity in the tillage layers. We ensured during our sampling that the thickness of the tillage layer was also nearly uniform. Wagai et al. (2013) and Asano and Wagai (2015) also used only six or five samples from the same experimental field. Following your comment, we added details about the experimental field in the revised manuscript.( 2.1 Soil characteristics).
Comment 4:
(1)L87: you separated three aggregate size classes (0.25-2, 0.053-0.25, <0.053mm), why there have four REOs? One is redundant?
(2)L95: I doubt that you can broke down to pass the soil through a 2-mm sieve just by hand without other tools after oven-dried. The wet-dry cycle of labeling process had clumped the soil.
(3)L114: how do you add the 13 ml of ultrapure water to avoid the rewet effect on aggregate turnover?
(4)L119-120: more details of the incubation. The top of box is open or close?
Reply4: We feel sorry for the inconvenience brought to the reviewer. In the previous manuscript, the REE oxides characteristic, labelling, sieving and incubation processes were all placed in 2.2 REO-labeled aggregates, resulting in a confusing and unreadable experimental design.
Therefore, based on comments, we have restructured the 2.3 experimental design section in revised manuscript, to bring it more consistent with the topic, and added more details to improve the reader's understanding.
(1)L87: you separated three aggregate size classes (0.25-2, 0.053-0.25, <0.053mm), why there have four REOs? One is redundant?
(1)We feel really sorry for our carelessness. Three REE oxides were selected as aggregate tracers, the 2-0.25 mm fraction labeled by Gd2O3 (A), 0.25-0.053 mm fraction labeled by Sm2O3 (B), and <0.053 mm fraction labeled by Nd2O3 (C). The REE oxides characteristics is described in2 REE oxides Characteristics.
(2)L95: I doubt that you can broke down to pass the soil through a 2-mm sieve just by hand without other tools after oven-dried. The wet-dry cycle of labeling process had clumped the soil.
(2)Thank you for your rigorous consideration. As much as the reviewer thinks so, there are many clods of soil that are difficult to break up by hand due to complete drying. Therefore, when the samples were dry and not sticky, the bulks were gently broken by hand with gloves. The details were added in 3.1 Labeling process.
(3)L114: how do you add the 13 ml of ultrapure water to avoid the rewet effect on aggregate turnover?
(3) We feel sorry that we did not provide enough information in the previous manuscript. we considered that the rewet effect on aggregate turnover may not need to be avoided. The transformation paths of three aggregate fractions were divided into (1) turnover directly caused by the labeling and sieving processes (at 0 days incubation); and (2) turnover caused by soil microorganisms during the incubation process (at 7,14,21,28 days incubation). The effect of the labeling, sieving and recombination processes on aggregate turnover was represented, by the turnover pathways of the aggregates at 0d in incubation. This section was described in 3 Experimental design.
(4)L119-120: more details of the incubation. The top of box is open or close?
(4) We gratefully appreciate for your valuable comment. Following your suggestion, more details about the incubation process were added in 2.3.4 Incubation process.
Comment 5:L175: where is the calculation of aggregate turnover rate? I can not find in the Appendix S1.
Reply5: We feel sorry for the inconvenience brought to the reviewer. In the revised manuscript, we have (1) introduced the calculation procedure in 2.5.1 Calculation of soil aggregate turnover; (2) inserted the schematic diagram of aggregate turnover, to make it easier for readers to understand.
Results
Comment 6: The authors showed lots of information in the text, without emphasizing the important information associated with the topic. For example, the effectivity of REOs labeling in tracing aggregate turnover has been widely proved, it is not an important information here. So, Fig.3 can be put in appendix rather than in text, and associated text should be more concise. Figs. 1 and 2 also can be merged.
Reply6: We gratefully appreciate for your valuable comment. Following your suggestion, we restructured the result section to incorporate 1) the effects of labelling, sieving and recombination processes (0d incubation) on organic matter; 2) the effects of labeling, sieving and recombination processes (0d incubation) on the distribution of agglomerates; 3) to verify the feasibility of REE oxides as tracers for Andisols; 4) the turnover pathways of aggregates during incubation; 5) the organic matter dynamics during incubation. This is actually the process of our experiment, not the validation of the research topic.
In the revised manuscript, to fit the research topic, we restructured the RESULT section as 1) The effect of labeling and sieving processes on Andisols aggregate turnover; 2) The effect of labeling and sieving processes on soil organic carbon fractions; 3) The effects on the quantitative study of the relationship between aggregate turnover and organic carbon dynamics. The modified Result section is as follows:
3.1The effect of labeling and sieving processes on Andisols aggregate turnover
3.1.1 verification of REE oxides as tracers of Andisols aggregate
3.1.2 Soil aggregate turnover pathways
3.2 The effect of labeling and sieving processes on soil organic carbon fractions
3.3 The effects on the quantitative study of the relationship between aggregate turnover and organic carbon dynamics.
In response to your question about the importance of the verification of the feasibility of using REE oxides as aggregate tracers, we hope to be able to provide an explanation. In previous studies we have found that REE oxides do not track 2-5mm fractions of Andisols very well during labeling (relevant manuscripts have been submitted and we hope that reviewers could continue to be interested in our studies). Therefore, in this study we needed to first ensure that REE oxides could be used as tracers to track Andisols <2mm fractions aggregate turnover, and then, use REE oxides to quantify aggregate turnover.
Comment 7: L194:why the format of Table 1 differs from other tables? And I feel uncomfortable with the unit in Table 1. g kg-1soil for TOC, fPOM, oPOM and HF and mg kg-1soil for MBC and DOC are more commonly used.
Reply7: Thank you so much for your careful check. As less attention has been paid to the effects of REE oxides addition, labelling, sieving and recombination processes on soil organic carbon in previous studies. Therefore, in this study, five treatments were designed as follows: (1) soil without REE oxides labeling and sieving processes (background treatment, BG), (2) soil with dry sieving and REE oxides labeling (REO-labeled and dry sieved treatment, REO-D), (3) soil with wet sieving and REE oxides labeling (REO-labeled and wet sieved treatment, REO-W), (4) soil with dry sieving but without REE oxides labeling (dry sieved treatment, CK-D), and (5) soil with wet sieving but without REE oxides labeling (wet sieved treatment, CK-W). Based on this design, we were able to determine the effect of REE oxides addition on the organic carbon fraction of soil aggregates by comparing the REO-D treatment with the CK-D treatment, the REO-W treatment with the CK-W treatment, and the effect of labeling and sieving processes on the organic matter fraction of the soil by comparing the BG treatment with other treatments.
Following your suggestion, g kg-1soil for TOC, fPOM, oPOM and HF and mg kg-1soil for MBC and DOC were used in Table3, and the relevant descriptions of the table were revised accordingly (3.2.1 The effect of labeling and sieving processes on soil organic carbon fractions after labeling and sieving processes).
Comment 8: Fig.7: Why do not show the absolute value of soil C fractions such as MBC and DOC? I think use the absolute value is more clearly than the proportions of them in SOC (the values are too low) to assess the effects of REOs labeling and sieving methods.
Reply 8: We feel sorry for the inconvenience brought to the reviewer. Following your suggestion, we have replaced the proportions of OC fractions in SOC with the absolute value in the figure and revised the description of the figures.
Discussion
Comment 9: I completely agree with the comments of another review about the discussion.
Besides, for section 4.3, authors paid more attention to discuss the aggregate turnover dynamics, where is the discussion of comparing the effects of labeling process and sieving method on aggregate turnover? I think it is the key point needing to be discussed.
Reply 9: We feel sorry for the inconvenience brought to the reviewer. We have tried too much to illustrate the feasibility of using soil organic carbon fractions and REE oxides to quantify soil organic carbon dynamics and soil aggregate turnover, respectively, and to analyze their relationship. This resulted in the Discussion section being inconsistent with the research topic.
(1)We discussed the effect of labeling and sieving processes on the aggregate turnover from 1)the feasibility of REE oxides as Andisols aggregate tracers; 2) The transformation of aggregate turnover pathways before incubation (0d); 3) The transformation of aggregate turnover pathways during incubation;4) the aggregate turnover rate during incubation(1 Effects of labeling and sieving processes on Andisols aggregate).
(2)We discussed the effects of the labeling and sieving process on soil organic carbon in terms of 1) the effect of wet sieving on soil organic carbon dynamics; 2) the effect of dry sieving on soil organic carbon dynamics(4.2 Effects of REE oxide labeling and sieving processes on soil organic carbon);
(3)We discussed the feasibility of using soil organic carbon fractions to analyze the relationship between organic carbon dynamics and aggregate turnover (Effects of the quantitative study of the relationship between aggregate turnover and organic carbon dynamics).
Comment 10: L334-338: explaining why wet sieving removes most fPOM. Does the dry sieving reduce fPOM because of the removal of fine roots and debris? The fine roots and debris should be removed before experiment, them were not pick out clean?
Reply 10: Thanks for your careful checks,we feel sorry that we did not provide enough information about dry sieving and wet sieving methods. The soil samples were root-picked prior to sieving, so both the wet and dry sieving treatments included fPOC loss from the root-picking process. However, during the wet sieving process, we found some free particulate organic matter floating on the water after sieving and this part of the POC was lost during the sieving process. Therefore, the fPOC of the wet sieving aggregates was significantly lower than that of the dry sieving aggregates and the BG treatment in this study.
Comment 11:
(1)Some problems of format at L345, 351, 361.
(2)L394-395: If the relationship between oPOM and aggregate fractions is important, please discuss it more in-depth, not just depict the result. If it is not important in this study, it is not necessary to show.
(3)L415: “The HF generated by aggregate breakdown cannot accumulate into aggregates, allowing it to accumulate on the outside and consequently increase the proportion of fPOM”, please attach the reference. I do not think the accumulation of HF can increase fPOM. They are varying in size, density and properties (e.g. C/N), two different concepts. The soil continuum model (Lehmann, J., Kleber, M., 2015. The contentious nature of soil organic matter. Nature 528: 60-68) suggested that fPOM can be degraded into HF with microbial processing, and it is an irreversible process.
Reply 11: It is really a giant mistake to the whole quality of our article. We feel sorry for our carelessness. We have corrected it and we also feel great thanks for your point out.Following the suggestion by you and the other anonymous reviewer, we removed the extensive discussion of the relationship between oPOM and aggregate fractions, and restructured the discussion in terms of labelling, sieving processes for 1) aggregate turnover; 2) organic matter dynamics; and 3) quantitative analysis of the relationship between organic matter and aggregates.
In response to L415: "The HF generated by aggregate breakdown cannot accumulate into aggregates, allowing it to accumulate on the outside and consequently increase the proportion of fPOM", not from other literature, but for the quantitative analysis of soil organic matter dynamics in relation to agglomerates during wet sieving, we found an increase in fPOC content and a decrease in oPOC and HF during incubation, and therefore feel that the increase in fPOC may be related to HF. The inaccurate description has been removed following your suggestion. The revised Discussion section is as supplement.
Conclusion
Comment 12: Do not simply repeat the results, but show the main findings and implications.
Reply 12: Thank you for your valuable suggestion.
Conclusions based on the research topic and discussion were obtained from aggregate turnover and soil organic carbon dynamics, respectively. The addition of REE oxides would have no effect on the Andisols aggregate turnover and organic carbon dynamics, but the REE oxides labeling and sieving processes would have effects on soil aggregates and soil organic carbon.
Acknowledgements
We gratefully thanks for the precious time the reviewer spent making constructive remarks.
Reference
Based on your suggestions, the Introduction and Discussion sections have been revised a lot, so we have restructured the Reference section.(8 Reference).
We hope you will find our revised manuscript acceptable for publication.
Yours sincerely,
Wang Yike
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AC3: 'Reply on RC2', Wang Yike, 03 Dec 2022
Status: closed
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RC1: 'Comment on egusphere-2022-728', Anonymous Referee #1, 21 Oct 2022
This manuscript from Wang et al. aims at elucidating the effect of rare earth oxide labeling and sieving methods on aggregate turnover and carbon dynamics. To reach their objectives, they conducted labelling and incubation experimentations with dry or wet sieving methods. SOC fractions (DOC, fPOM, MBC and HF) were detected and their relationship with aggregate dynamics were analyzed herein.
Indeed, little researches have reported the effects of labelling and sieving processes on SOC fractions, it is interesting to investigate the discrepancy caused by various methods. But in my view, authors do not provide a clear response to the topic, the research questions are not well stated in the introduction and the findings are not fully discussed in the discussion part. Besides, I doubt the calculation on aggregate turnover rate, which is different from the calculation proposed by De Gryze et al. and Peng et al. For these reasons, I do not recommend the publication of the article in SOIL.
Introduction
The title focused on two factors, namely labelling processes and sieving methods, to aggregate turnover and SOC. Insufficient statements on the importance of these two factors are provided, instead, authors illustrated more the interaction between SOC and soil structure.
Materials and methods
L80 More details on the investigated soil should be provided, such as the initial SOC content, sand/clay/silt content, bulk density etc.
L90-100 Four oxides were used for labelling, but only 3 aggregate fractions were used? So which three oxides you used herein? How to get the recombined soil columns? The soil content and bulk density of these recombined columns? How many soil columns in total? More detailed information is needed.
L120 What do you mean by “regularly”? Every two days?
L125 How much soil is used for dry/wet sieving and SOC fraction detection, respectively?
L175 How to calculate the aggregate turnover?
Results
L190 Since the results and discussion parts are separated herein, no reference should be included in results part.
L200 Please explain the meaning of “unaffected carbon pools”.
L210 It will be easier for readers to follow when 0.25- to 2-, 0.053- to 0.25-, and <0.053-mm are replaced by 0.25-2 mm, 0.053-0.25 mm and <0.053 mm.
L265 I doubt the calculation on aggregate turnover. Take turnover rate of 0.25-2 mm at 7 days as an example, 0.75=(4.58+0.68)/7, it seems that the formation processes are not taken into consideration, which is different from the calculation proposed by De Gryze et al. and Peng et al..
L270 According to Fig.5, the breakdown and formation of dry sieving aggregates occurred not only the first week.
L275 Transformation pathways in Fig. 6 are much smaller than published data. Why? No further discussion are displayed.
L300 There are two “Wet-MBC” in Fig.7a? To present the same SOC fraction, authors used the same color in a, while used the same shape in b, please keep them uniformed.
Discussion
There are lots of repetition of results. No highlights were proposed and discussed here. For section 4.2, lots of publications have proved it, there is no need to discuss again. For section 4.4, the relationship between SOC and aggregate are analyzed, which should be displayed in results rather than discussion part.
Conclusion
It is abstract, not conclusion. The main findings/conclusions, rather than results, are supposed to be included here.
Citation: https://doi.org/10.5194/egusphere-2022-728-RC1 -
AC1: 'Reply on RC1', Wang Yike, 07 Nov 2022
We gratefully thank the editor and reviewer for the time spent making their constructive remarks and helpful suggestion, which has significantly raised the quality of the manuscript and has enabled us to improve the manuscript. Each suggested revision and comment, brought forward by the reviewer was accurately incorporated and considered. Below the reviewer's comments are response point by point and revisions are indicated.
General Comments: This manuscript from Wang et al. aims at elucidating the effect of rare earth oxide labeling and sieving methods on aggregate turnover and carbon dynamics. To reach their objectives, they conducted labelling and incubation experimentations with dry or wet sieving methods. SOC fractions (DOC, fPOM, MBC and HF) were detected and their relationship with aggregate dynamics were analyzed herein.
Indeed, little research have reported the effects of labelling and sieving processes on SOC fractions, it is interesting to investigate the discrepancy caused by various methods. But in my view, the authors do not provide a clear response to the topic, the research questions are not well stated in the introduction and the findings are not fully discussed in the discussion part. Besides, I doubt the calculation on aggregate turnover rate, which is different from the calculation proposed by De Gryze et al. and Peng et al. For these reasons, I do not recommend the publication of the article in SOIL.Response: We greatly appreciate the reviewer's insightful comments. In fact, while processing the data for this manuscript, we found that there was perhaps a hidden innovation, the application of soil organic fractions to quantify soil organic matter, with REE oxides to track the aggregate turnover. In previous studies, Peng et al. (2017) analyzed the organic matter dynamics by adding 13C-labeled glucose to REE oxides labeled soils and determining the 13C content in different aggregate fractions. Subsequently, M. Halder et al. (2022) used eleven organic materials characterized in terms of nutrient stoichiometry, biochemical features and carbon (C) functional groups, to determine which characteristics of organic materials control soil aggregate turnover. However, in the following studies, we found that it would be too expensive to use carbon isotope methods in field experiments or to determine the contribution of organic matter monomers (e.g. galactosamine) for aggregate turnover. This is why a large number of descriptions of the relationship between aggregates and organic carbon have appeared in previous manuscripts.
The main reason for your query about the calculation is that the transformation paths of three aggregate fractions were divided into (1) turnover directly caused by the labeling and sieving processes (at 0 days incubation); (2) turnover caused by soil microorganisms during the incubation process (at 7,14,21,28 days incubation). The excessively low transformation of aggregate turnover pathways is due to the subtraction of transformation before incubation (0 days). We will provide a detailed response to your question about the aggregate turnover calculation in a point-to-point response.
Based on your suggestions, we have restructured the logical framework of the manuscript and will respond to your suggestions in a point-to-point response. In the revised version of the manuscript, we have refined the abstract and main text (especially the Introduction, the Results and the Discussion sections) to make the paper easier to read, the procedure for the calculation of aggregate turnover, which was originally placed in the appendix, has also been collated into 2.5.1 Calculation of soil aggregate turnover in the revised manuscript.
In the Introduction section, we have (1) restructured the framework of the manuscript to make the manuscript more palatable to general readers; (2) outlined the major assumptions briefly; (3) deleted unnecessary description of the relationship between aggregate turnover and soil organic carbon dynamics to make the introduction section more relevant to the topic.
In the Material and method section, we have (1) introduced a more specific description of the Andisols soil samples in 2.1 Soil characteristics; （2）Changed the description of the experiment design in 2.3 Experiment design to make it more consistent with the research topic. (3) Added a flow chart of the recombination process in 2.3.1 Recombination process, to make the recombination process more accessible to the readers; (4) Added 2.5.1Calculation of soil aggregate turnover in the revised manuscript, from the original appendix and added Figure2 The 6 possible transformation pathways of aggregate.
In the Results section, we have (1) modified the structure of the result section according to the revised experiment design, and described the effect of the labeling and sieving process on aggregate turnover and organic carbon fractions, respectively; (2)added transformation aggregates turnover pathways before incubation (0 days) in 3.1.2 Soil aggregate turnover pathways; (3) Added soil organic carbon fraction dynamics of BG treatment during incubation in 3.2.2 The effect of labeling and sieving processes on SOC fractions during incubation process; (4) placed the relationship between aggregate turnover and organic matter dynamics in 3.3 The effects on the quantitative study of the relationship between aggregate turnover and organic matter dynamics.
In the Discussion section, we have reorganized the discussion according to the research topic and your comments. the impact of the labeling and sieving processes on soil aggregate turnover and soil organic carbon fractions were discussed, respectively.
In the Conclusion section, We have (1) identified that labeling and sieving processes could affect aggregate turnover and soil organic carbon fractions; (2) made suggestions for eliminating the disturbances.
Point-to-point response
Comment 1: Introduction, The title focused on two factors, namely labelling processes and sieving methods, to aggregate turnover and SOC. Insufficient statements on the importance of these two factors are provided, instead, authors illustrated more the interaction between SOC and soil structure.
Reply1: We gratefully appreciate for your valuable comment. In the Introduction section, we have (1) deleted unnecessary description of the relationship between aggregate turnover and soil organic carbon dynamics; (2)Restructured the introduction section from labeling and sieving processes on aggregate turnover and organic matter dynamics, to make the introduction section more relevant to the research topic(as shown in supplement).
Comment 2: L80 More details on the investigated soil should be provided, such as the initial SOC content, sand/clay/silt content, bulk density etc.
Reply2: We gratefully appreciate for your valuable comment. We provide the soil properties in 2.1Soil characteristics in the revised manuscript ( 2.1 Soil characteristics, as shown in supplement).
Comment 3: L90-100 Four oxides were used for labelling, but only 3 aggregate fractions were used? So which three oxides you used herein? How to get the recombined soil columns? The soil content and bulk density of these recombined columns? How many soil columns in total? More detailed information is needed.
L120 What do you mean by “regularly”? Every two days?
Reply3: We feel sorry for the inconvenience brought to the reviewer. The comment relates to the labeling process, the recombination process, and the incubation process, therefore we will reply in three parts.
(1) We have placed the labeling process in the 3 Experiment design section, together with the sieving process, recombination process and incubation process. And the labeling process is described in 2.3.1 Labeling process (as shown in the supplement ).
(2)For details of the recombination process are described in 2.3.3 The recombination process and the protocol for recombining aggregates into recombined soils was added, as shown in Figure 1 (as shown in the supplement).
(3)Details of the container for recombined soil and the way of maintaining soil moisture content were described in 2.3.4 Incubation process(as shown in the supplement).
Comment 4:L125 How much soil is used for dry/wet sieving and SOC fraction detection, respectively?
Reply4: Thank you for your rigorous consideration. We would like to respond to this comment in two parts:(1) sieving methods; and (2) soil organic carbon fractions.(1)For the dry/sieving aggregate fraction. Because five treatments were designed in this experiment, we prepared 500g soil samples for each treatment, except for the BG treatment, the treatments involved the labeling process. After labeling process, all labeled soil samples were sieved and recombination, 50 g of sample was sieved at each time (as shown in 2.3.2 Sieving process).
1) Where the descriptions of five treatments are described as: (1) soil without REE oxides labeling and sieving processes (background treatment, BG), (2) soil with dry sieving and REE oxides labeling (REO-labeled and dry sieved treatment, REO-D), (3) soil with wet sieving and REE oxides labeling (REO-labeled and wet sieved treatment, REO-W), (4) soil with dry sieving but without REE oxides labeling (dry sieved treatment, CK-D), and (5) soil with wet sieving but without REE oxides labeling (wet sieved treatment, CK-W).
2) Where the descriptions of the sieving process are described( as shown in supplements)
(2) For the soil organic carbon fractions. Different weights of soil samples were selected according to soil organic carbon fraction determination methods. Where, Total organic carbon(TOC): 0.15–0.20 g; Microbial biomass carbon(MBC):20.00g; Dissolved organic carbon (DOC): 20.00g; free particulate organic carbon (fPOC), occluded particulate organic carbon (oPOC), and a heavy fraction (HF):4.00g. These details about weight have been supplemented in 2.4.2 Analysis of soil organic carbon fractions (as shown in the supplement)
Comment 5:L175 How to calculate the aggregate turnover?
Reply5: We feel sorry for the inconvenience brought to the reviewer. The previous manuscript placed the calculation process in the appendix, which may have caused inconvenience to readers. Therefore, in revised manuscript, we have (1) introduced the calculation procedure in 2.5.1 Calculation of soil aggregate turnover; (2) inserted the schematic diagram of aggregate turnover, to make it easier for readers to understand(as shown in supplements).
Results
Comment 6: L190 Since the results and discussion parts are separated herein, no reference should be included in results part.
Reply6: We gratefully appreciate for your valuable comment. Following your suggestion, the discussion and references in the Results section have been moved to the Discussion section.
Comment 7:L200 Please explain the meaning of “unaffected carbon pools”.
Reply7: Thank you so much for your careful check. In previous manuscripts, as oPOM and HF fractions in Table 1 were less affected by REE oxides addition, labeling, sieving and recombination processes, we have attempted to unify this part of the soil organic carbon fractions into 'unaffected carbon pools' for discussion. In the revised manuscript, we did not add new concepts( like 'unaffected carbon pools') , but described all carbon fractions according to Table3(as shown in the supplement).
Comment 8:L210 It will be easier for readers to follow when 0.25- to 2-, 0.053- to 0.25-, and <0.053-mm are replaced by 0.25-2 mm, 0.053-0.25 mm and <0.053 mm.
Reply 8: We feel sorry for the inconvenience brought to the reviewer. Following your suggestion, we have replaced 0.25- to 2-, 0.053- to 0.25-, and <0.053-mm with 0.25-2 mm, 0.053-0.25 mm and <0.053 mm in revised manuscript.
Comment 9:L265 I doubt the calculation on aggregate turnover. Take turnover rate of 0.25-2 mm at 7 days as an example, 0.75=(4.58+0.68)/7, it seems that the formation processes are not taken into consideration, which is different from the calculation proposed by De Gryze et al. and Peng et al.
L270 According to Fig.5, the breakdown and formation of dry sieving aggregates occurred not only the first week.
L275 Transformation pathways in Fig. 6 are much smaller than published data. Why? No further discussion are displayed.
Reply 9: We totally understand the reviewer’s concern. These three questions are about the transformation of aggregate turnover pathways, so we would like to provide better responses to your comments.
In earlier manuscripts, we were too concerned with the relationship between soil aggregate turnover and soil organic matter, and therefore removed the transformation of aggregate turnover pathways before incubation(0 days) as a disturbance. Actually, to elucidate the influence of the labeling and sieving processes on the aggregates turnover, The transformation paths of three aggregate fractions were divided into (1) turnover directly caused by the labeling and sieving processes (at 0 days incubation); and (2) turnover caused by soil microorganisms during the incubation process (at 7,14,21,28 days incubation). Soil samples obtained from 7, 14, 21 and 28 days of incubation included both the labeling-sieving and recombination processes and the incubation process, whereas samples from 0-day incubation included only the labeling, sieving and recombination processes. Therefore, the turnover pathways of the incubation process are calculated as the difference between the turnover pathways of different incubation days (7, 14, 21, 28days) and the turnover pathways of 0 days of incubation.
In the revised manuscript, we have
(1) Introduced the labeling and sieving process and the incubation process in 2.3 Experimental design describe as:
A series of experiments were conducted in this study. First, The feasibility of REE oxides as tracers to track Andisols aggregate turnover was determined. Then, we divide the effects of REE oxides on Andisols aggregate turnover and organic carbon dynamics into two processes: labeling and sieving processes and incubation process. In the labeling and sieving processes, REE oxides addition, labeling method and sieving method are the main causes of soil organic carbon and aggregate turnover. And in the incubation process variations in soil organic carbon dynamics and aggregate turnover are caused by initial soil organic carbon fractions differences and the soil microbial.
(2) Added Equation(7) in the calculation section as a supplement to the calculation procedures.
Because the Andisols samples were subjected to the labeling process, the sieving process, and the recombination process, and finally to incubation, The labeling, sieving and recombination processes have a destructive effect on aggregates. Soil samples obtained from 7-, 14-, 21- and 28-days incubation included both the labeling-sieving and recombination processes and the incubation process(Ktx), whereas samples from 0-day incubation included only the labeling, sieving and recombination processes (Kt0), then the contribution of the incubation effect to aggregate turnover is calculated as: Kinc= Ktx-Kt0.
(3) Included images and analysis of the transfer pathways between the three aggregate size fractions before incubation(0day) in 3.1.2 Soil aggregate turnover pathways(as shown in supplement).
(4) Compared with Peng et al. (2017) and M. Halder et al. (2022) for the transformation of aggregate turnover pathways and turnover rates in Discussion section 4.1Effects of labeling and sieving processes on Andisols aggregate(as shown in supplement).
Comment 10:L300 There are two “Wet-MBC” in Fig.7a? To present the same SOC fraction, authors used the same color in a, while used the same shape in b, please keep them uniformed.
Reply 10: Thank you so much for your careful check. We apologize for our carelessness. In earlier manuscript, the grey circle represents the "Wet-DOC" instead of "Wet-MBC" in Fig. 7a. In the revised manuscript we have (1) corrected the error in the figure legend; (2) increased the dynamic of the BG treatment organic carbon fractions during incubation(3.2.2 The effect of labeling and sieving processes on SOC fractions during incubation processes, as shown in supplement).
Discussion
Comment 11:There are lots of repetition of results. No highlights were proposed and discussed here. For section 4.2, lots of publications have proved it, there is no need to discuss again. For section 4.4, the relationship between SOC and aggregate are analyzed, which should be displayed in results rather than discussion part.
Reply11:We feel sorry for the inconvenience brought to the reviewer. We have tried too much to illustrate the feasibility of using soil organic carbon fractions and REE oxides to quantify soil organic carbon dynamics and soil aggregate turnover, respectively, and to analyze their relationship. This resulted in the Discussion section being inconsistent with the research topic.
(1)We discussed the effect of labeling and sieving processes on the aggregate turnover from 1)the feasibility of REE oxides as Andisols aggregate tracers; 2) The transformation of aggregate turnover pathways before incubation (0d); 3) The transformation of aggregate turnover pathways during incubation;4) the aggregate turnover rate during incubation(4.1 Effects of labeling and sieving processes on Andisols aggregate,as shown in supplement).
(2) We discussed the effects of the labeling and sieving process on soil organic carbon in terms of 1) the effect of wet sieving on soil organic carbon dynamics; 2) the effect of dry sieving on soil organic carbon dynamics; 3) the feasibility of using soil organic carbon fractions to analyze the relationship between organic matter dynamics and aggregate turnover. (4.2 Effects of REE oxide labeling and sieving processes on soil organic carbon, as shown in supplement)
Conclusion
Comment 12: It is abstract, not conclusion. The main findings/conclusions, rather than results, are supposed to be included here.
Reply12: Thank you for your valuable suggestion.
Conclusions based on the research topic and discussion were obtained from aggregate turnover and soil organic carbon dynamics, respectively. The addition of REE oxides would have no effect on the Andisols aggregate turnover and organic matter dynamics, but the REE oxides labeling and sieving processes would have effects on soil aggregates and soil organic carbon(as shown in supplement).
Acknowledgement
We gratefully thanks for the precious time the reviewer spent making constructive remarks.
Add: We also acknowledge one anonymous reviewer for helpful comments on an earlier draft of our manuscript.
Reference
Based on your suggestions, the Introduction and Discussion sections have been revised a lot, so we have restructured the Reference section. (8 Reference).
We hope you will find our revised manuscript acceptable for publication.
Yours sincerely,
Wang Yike
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AC2: 'Reply on RC1', Wang Yike, 07 Nov 2022
We gratefully thank the editor and reviewer for the time spent making their constructive remarks and helpful suggestion, which has significantly raised the quality of the manuscript and has enabled us to improve the manuscript. Each suggested revision and comment, brought forward by the reviewer was accurately incorporated and considered. Below the reviewer's comments are response point by point and revisions are indicated.
General Comments: This manuscript from Wang et al. aims at elucidating the effect of rare earth oxide labeling and sieving methods on aggregate turnover and carbon dynamics. To reach their objectives, they conducted labelling and incubation experimentations with dry or wet sieving methods. SOC fractions (DOC, fPOM, MBC and HF) were detected and their relationship with aggregate dynamics were analyzed herein.
Indeed, little research have reported the effects of labelling and sieving processes on SOC fractions, it is interesting to investigate the discrepancy caused by various methods. But in my view, the authors do not provide a clear response to the topic, the research questions are not well stated in the introduction and the findings are not fully discussed in the discussion part. Besides, I doubt the calculation on aggregate turnover rate, which is different from the calculation proposed by De Gryze et al. and Peng et al. For these reasons, I do not recommend the publication of the article in SOIL.Response: We greatly appreciate the reviewer's insightful comments. In fact, while processing the data for this manuscript, we found that there was perhaps a hidden innovation, the application of soil organic fractions to quantify soil organic matter, with REE oxides to track the aggregate turnover. In previous studies, Peng et al. (2017) analyzed the organic matter dynamics by adding 13C-labeled glucose to REE oxides labeled soils and determining the 13C content in different aggregate fractions. Subsequently, M. Halder et al. (2022) used eleven organic materials characterized in terms of nutrient stoichiometry, biochemical features and carbon (C) functional groups, to determine which characteristics of organic materials control soil aggregate turnover. However, in the following studies, we found that it would be too expensive to use carbon isotope methods in field experiments or to determine the contribution of organic matter monomers (e.g. galactosamine) for aggregate turnover. This is why a large number of descriptions of the relationship between aggregates and organic carbon have appeared in previous manuscripts.
The main reason for your query about the calculation is that the transformation paths of three aggregate fractions were divided into (1) turnover directly caused by the labeling and sieving processes (at 0 days incubation); (2) turnover caused by soil microorganisms during the incubation process (at 7,14,21,28 days incubation). The excessively low transformation of aggregate turnover pathways is due to the subtraction of transformation before incubation (0 days). We will provide a detailed response to your question about the aggregate turnover calculation in a point-to-point response.
Based on your suggestions, we have restructured the logical framework of the manuscript and will respond to your suggestions in a point-to-point response. In the revised version of the manuscript, we have refined the abstract and main text (especially the Introduction, the Results and the Discussion sections) to make the paper easier to read, the procedure for the calculation of aggregate turnover, which was originally placed in the appendix, has also been collated into 2.5.1 Calculation of soil aggregate turnover in the revised manuscript.
In the Introduction section, we have (1) restructured the framework of the manuscript to make the manuscript more palatable to general readers; (2) outlined the major assumptions briefly; (3) deleted unnecessary description of the relationship between aggregate turnover and soil organic carbon dynamics to make the introduction section more relevant to the topic.
In the Material and method section, we have (1) introduced a more specific description of the Andisols soil samples in 2.1 Soil characteristics; （2）Changed the description of the experiment design in 2.3 Experiment design to make it more consistent with the research topic. (3) Added a flow chart of the recombination process in 2.3.1 Recombination process, to make the recombination process more accessible to the readers; (4) Added 2.5.1Calculation of soil aggregate turnover in the revised manuscript, from the original appendix and added Figure2 The 6 possible transformation pathways of aggregate.
In the Results section, we have (1) modified the structure of the result section according to the revised experiment design, and described the effect of the labeling and sieving process on aggregate turnover and organic carbon fractions, respectively; (2)added transformation aggregates turnover pathways before incubation (0 days) in 3.1.2 Soil aggregate turnover pathways; (3) Added soil organic carbon fraction dynamics of BG treatment during incubation in 3.2.2 The effect of labeling and sieving processes on SOC fractions during incubation process; (4) placed the relationship between aggregate turnover and organic matter dynamics in 3.3 The effects on the quantitative study of the relationship between aggregate turnover and organic matter dynamics.
In the Discussion section, we have reorganized the discussion according to the research topic and your comments. the impact of the labeling and sieving processes on soil aggregate turnover and soil organic carbon fractions were discussed, respectively.
In the Conclusion section, We have (1) identified that labeling and sieving processes could affect aggregate turnover and soil organic carbon fractions; (2) made suggestions for eliminating the disturbances.
Point-to-point response
Comment 1: Introduction, The title focused on two factors, namely labelling processes and sieving methods, to aggregate turnover and SOC. Insufficient statements on the importance of these two factors are provided, instead, authors illustrated more the interaction between SOC and soil structure.
Reply1: We gratefully appreciate for your valuable comment. In the Introduction section, we have (1) deleted unnecessary description of the relationship between aggregate turnover and soil organic carbon dynamics; (2)Restructured the introduction section from labeling and sieving processes on aggregate turnover and organic matter dynamics, to make the introduction section more relevant to the research topic(as shown in supplement).
Comment 2: L80 More details on the investigated soil should be provided, such as the initial SOC content, sand/clay/silt content, bulk density etc.
Reply2: We gratefully appreciate for your valuable comment. We provide the soil properties in 2.1Soil characteristics in the revised manuscript ( 2.1 Soil characteristics, as shown in supplement).
Comment 3: L90-100 Four oxides were used for labelling, but only 3 aggregate fractions were used? So which three oxides you used herein? How to get the recombined soil columns? The soil content and bulk density of these recombined columns? How many soil columns in total? More detailed information is needed.
L120 What do you mean by “regularly”? Every two days?
Reply3: We feel sorry for the inconvenience brought to the reviewer. The comment relates to the labeling process, the recombination process, and the incubation process, therefore we will reply in three parts.
(1) We have placed the labeling process in the 3 Experiment design section, together with the sieving process, recombination process and incubation process. And the labeling process is described in 2.3.1 Labeling process (as shown in the supplement ).
(2)For details of the recombination process are described in 2.3.3 The recombination process and the protocol for recombining aggregates into recombined soils was added, as shown in Figure 1 (as shown in the supplement).
(3)Details of the container for recombined soil and the way of maintaining soil moisture content were described in 2.3.4 Incubation process(as shown in the supplement).
Comment 4:L125 How much soil is used for dry/wet sieving and SOC fraction detection, respectively?
Reply4: Thank you for your rigorous consideration. We would like to respond to this comment in two parts:(1) sieving methods; and (2) soil organic carbon fractions.(1)For the dry/sieving aggregate fraction. Because five treatments were designed in this experiment, we prepared 500g soil samples for each treatment, except for the BG treatment, the treatments involved the labeling process. After labeling process, all labeled soil samples were sieved and recombination, 50 g of sample was sieved at each time (as shown in 2.3.2 Sieving process).
1) Where the descriptions of five treatments are described as: (1) soil without REE oxides labeling and sieving processes (background treatment, BG), (2) soil with dry sieving and REE oxides labeling (REO-labeled and dry sieved treatment, REO-D), (3) soil with wet sieving and REE oxides labeling (REO-labeled and wet sieved treatment, REO-W), (4) soil with dry sieving but without REE oxides labeling (dry sieved treatment, CK-D), and (5) soil with wet sieving but without REE oxides labeling (wet sieved treatment, CK-W).
2) Where the descriptions of the sieving process are described( as shown in supplements)
(2) For the soil organic carbon fractions. Different weights of soil samples were selected according to soil organic carbon fraction determination methods. Where, Total organic carbon(TOC): 0.15–0.20 g; Microbial biomass carbon(MBC):20.00g; Dissolved organic carbon (DOC): 20.00g; free particulate organic carbon (fPOC), occluded particulate organic carbon (oPOC), and a heavy fraction (HF):4.00g. These details about weight have been supplemented in 2.4.2 Analysis of soil organic carbon fractions (as shown in the supplement)
Comment 5:L175 How to calculate the aggregate turnover?
Reply5: We feel sorry for the inconvenience brought to the reviewer. The previous manuscript placed the calculation process in the appendix, which may have caused inconvenience to readers. Therefore, in revised manuscript, we have (1) introduced the calculation procedure in 2.5.1 Calculation of soil aggregate turnover; (2) inserted the schematic diagram of aggregate turnover, to make it easier for readers to understand(as shown in supplements).
Results
Comment 6: L190 Since the results and discussion parts are separated herein, no reference should be included in results part.
Reply6: We gratefully appreciate for your valuable comment. Following your suggestion, the discussion and references in the Results section have been moved to the Discussion section.
Comment 7:L200 Please explain the meaning of “unaffected carbon pools”.
Reply7: Thank you so much for your careful check. In previous manuscripts, as oPOM and HF fractions in Table 1 were less affected by REE oxides addition, labeling, sieving and recombination processes, we have attempted to unify this part of the soil organic carbon fractions into 'unaffected carbon pools' for discussion. In the revised manuscript, we did not add new concepts( like 'unaffected carbon pools') , but described all carbon fractions according to Table3(as shown in the supplement).
Comment 8:L210 It will be easier for readers to follow when 0.25- to 2-, 0.053- to 0.25-, and <0.053-mm are replaced by 0.25-2 mm, 0.053-0.25 mm and <0.053 mm.
Reply 8: We feel sorry for the inconvenience brought to the reviewer. Following your suggestion, we have replaced 0.25- to 2-, 0.053- to 0.25-, and <0.053-mm with 0.25-2 mm, 0.053-0.25 mm and <0.053 mm in revised manuscript.
Comment 9:L265 I doubt the calculation on aggregate turnover. Take turnover rate of 0.25-2 mm at 7 days as an example, 0.75=(4.58+0.68)/7, it seems that the formation processes are not taken into consideration, which is different from the calculation proposed by De Gryze et al. and Peng et al.
L270 According to Fig.5, the breakdown and formation of dry sieving aggregates occurred not only the first week.
L275 Transformation pathways in Fig. 6 are much smaller than published data. Why? No further discussion are displayed.
Reply 9: We totally understand the reviewer’s concern. These three questions are about the transformation of aggregate turnover pathways, so we would like to provide better responses to your comments.
In earlier manuscripts, we were too concerned with the relationship between soil aggregate turnover and soil organic matter, and therefore removed the transformation of aggregate turnover pathways before incubation(0 days) as a disturbance. Actually, to elucidate the influence of the labeling and sieving processes on the aggregates turnover, The transformation paths of three aggregate fractions were divided into (1) turnover directly caused by the labeling and sieving processes (at 0 days incubation); and (2) turnover caused by soil microorganisms during the incubation process (at 7,14,21,28 days incubation). Soil samples obtained from 7, 14, 21 and 28 days of incubation included both the labeling-sieving and recombination processes and the incubation process, whereas samples from 0-day incubation included only the labeling, sieving and recombination processes. Therefore, the turnover pathways of the incubation process are calculated as the difference between the turnover pathways of different incubation days (7, 14, 21, 28days) and the turnover pathways of 0 days of incubation.
In the revised manuscript, we have
(1) Introduced the labeling and sieving process and the incubation process in 2.3 Experimental design describe as:
A series of experiments were conducted in this study. First, The feasibility of REE oxides as tracers to track Andisols aggregate turnover was determined. Then, we divide the effects of REE oxides on Andisols aggregate turnover and organic carbon dynamics into two processes: labeling and sieving processes and incubation process. In the labeling and sieving processes, REE oxides addition, labeling method and sieving method are the main causes of soil organic carbon and aggregate turnover. And in the incubation process variations in soil organic carbon dynamics and aggregate turnover are caused by initial soil organic carbon fractions differences and the soil microbial.
(2) Added Equation(7) in the calculation section as a supplement to the calculation procedures.
Because the Andisols samples were subjected to the labeling process, the sieving process, and the recombination process, and finally to incubation, The labeling, sieving and recombination processes have a destructive effect on aggregates. Soil samples obtained from 7-, 14-, 21- and 28-days incubation included both the labeling-sieving and recombination processes and the incubation process(Ktx), whereas samples from 0-day incubation included only the labeling, sieving and recombination processes (Kt0), then the contribution of the incubation effect to aggregate turnover is calculated as: Kinc= Ktx-Kt0.
(3) Included images and analysis of the transfer pathways between the three aggregate size fractions before incubation(0day) in 3.1.2 Soil aggregate turnover pathways(as shown in supplement).
(4) Compared with Peng et al. (2017) and M. Halder et al. (2022) for the transformation of aggregate turnover pathways and turnover rates in Discussion section 4.1Effects of labeling and sieving processes on Andisols aggregate(as shown in supplement).
Comment 10:L300 There are two “Wet-MBC” in Fig.7a? To present the same SOC fraction, authors used the same color in a, while used the same shape in b, please keep them uniformed.
Reply 10: Thank you so much for your careful check. We apologize for our carelessness. In earlier manuscript, the grey circle represents the "Wet-DOC" instead of "Wet-MBC" in Fig. 7a. In the revised manuscript we have (1) corrected the error in the figure legend; (2) increased the dynamic of the BG treatment organic carbon fractions during incubation(3.2.2 The effect of labeling and sieving processes on SOC fractions during incubation processes, as shown in supplement).
Discussion
Comment 11:There are lots of repetition of results. No highlights were proposed and discussed here. For section 4.2, lots of publications have proved it, there is no need to discuss again. For section 4.4, the relationship between SOC and aggregate are analyzed, which should be displayed in results rather than discussion part.
Reply11:We feel sorry for the inconvenience brought to the reviewer. We have tried too much to illustrate the feasibility of using soil organic carbon fractions and REE oxides to quantify soil organic carbon dynamics and soil aggregate turnover, respectively, and to analyze their relationship. This resulted in the Discussion section being inconsistent with the research topic.
(1)We discussed the effect of labeling and sieving processes on the aggregate turnover from 1)the feasibility of REE oxides as Andisols aggregate tracers; 2) The transformation of aggregate turnover pathways before incubation (0d); 3) The transformation of aggregate turnover pathways during incubation;4) the aggregate turnover rate during incubation(4.1 Effects of labeling and sieving processes on Andisols aggregate,as shown in supplement).
(2) We discussed the effects of the labeling and sieving process on soil organic carbon in terms of 1) the effect of wet sieving on soil organic carbon dynamics; 2) the effect of dry sieving on soil organic carbon dynamics; 3) the feasibility of using soil organic carbon fractions to analyze the relationship between organic matter dynamics and aggregate turnover. (4.2 Effects of REE oxide labeling and sieving processes on soil organic carbon, as shown in supplement)
Conclusion
Comment 12: It is abstract, not conclusion. The main findings/conclusions, rather than results, are supposed to be included here.
Reply12: Thank you for your valuable suggestion.
Conclusions based on the research topic and discussion were obtained from aggregate turnover and soil organic carbon dynamics, respectively. The addition of REE oxides would have no effect on the Andisols aggregate turnover and organic matter dynamics, but the REE oxides labeling and sieving processes would have effects on soil aggregates and soil organic carbon(as shown in supplement).
Acknowledgement
We gratefully thanks for the precious time the reviewer spent making constructive remarks.
Add: We also acknowledge one anonymous reviewer for helpful comments on an earlier draft of our manuscript.
Reference
Based on your suggestions, the Introduction and Discussion sections have been revised a lot, so we have restructured the Reference section. (8 Reference).
We hope you will find our revised manuscript acceptable for publication.
Yours sincerely,
Wang Yike
-
AC1: 'Reply on RC1', Wang Yike, 07 Nov 2022
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RC2: 'Comment on egusphere-2022-728', Anonymous Referee #2, 22 Nov 2022
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2022/egusphere-2022-728/egusphere-2022-728-RC2-supplement.pdf
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AC3: 'Reply on RC2', Wang Yike, 03 Dec 2022
Response to reviewers
We gratefully thank the editor and reviewer for the time spent making their constructive remarks and helpful suggestion, which has significantly raised the quality of the manuscript and has enabled us to improve the manuscript. Each suggested revision and comment, brought forward by the reviewer was accurately incorporated and considered. Below the reviewer's comments are response point by point and revisions are indicated.
'Comment on egusphere-2022-728', Anonymous Referee #2, 22 Nov 2022
General Comments: This manuscript by Wang et al. presented an important and interesting study of the effects of REOs labeling process and sieving methods on aggregate turnover and carbon dynamic. Researching soil aggregates and associated biogeochemical processes is a very time-consuming and laborious work, with the complex REOs labeling process makes it to be more difficult. Recently, studies focusing on aggregate turnover show a rising trend, while less researches have reported the role of labelling and sieving processes played in affecting aggregate turnover and soil C dynamics, which may obscure or even magnify the effect of treatments. Dividing the labeling process from the incubation (or other treatments) thus is pivotal for accurately assess the real aggregate turnover dynamics and soil C dynamics. Indeed, the authors found that labeling process and sieving method affect aggregate turnover and soil C fractions (particularly labile C fraction, i.e., DOC, MBC) more intensively than incubation. However, the text has low readability. The logic is very confusing, and the authors seem unable to catch the highlights and key points of the story. Additionally, some key information about the calculations do not show in article. I very appreciate with the work and its significance the authors done. However, I feel a pity that the authors show the story in a not good way. So, I do not recommend the publication of the article in SOIL. The best result is resubmission after major revision.
Response: We greatly appreciate the reviewer's insightful comments. In fact, while processing the data for this manuscript, we found that there was perhaps a hidden innovation, the application of soil organic fractions to quantify soil organic carbon, with REE oxides to track the aggregate turnover. In previous studies, Peng et al. (2017) analyzed the organic carbon dynamics by adding 13C-labeled glucose to REE oxides labeled soils and determining the 13C content in different aggregate fractions. Subsequently, M. Halder et al. (2022) used eleven organic materials characterized in nutrient stoichiometry, biochemical features and carbon (C) functional groups, to determine which characteristics of organic materials control soil aggregate turnover. However, in our following studies, we found that it would be too expensive to use carbon isotope methods in field experiments or to determine the contribution of organic carbon monomers (e.g. galactosamine) for aggregate turnover. This is why some parts focus on the effect of labeling and sieving processes on aggregate and SOM dynamics, and some parts focus on the descriptions of the relationship between aggregates and organic carbon in previous manuscripts, Which resulted in the manuscript's logic seeming pretty confusing and not well readable. Apologies again to the reviewers.
Based on your suggestions, we have restructured the logical framework of the manuscript and will respond to your suggestions in a point-to-point response. In the revised version of the manuscript, we have refined the abstract and main text (especially the Introduction, the Results and the Discussion sections) to make the paper easier to read, the procedure for the calculation of aggregate turnover, which was originally placed in the appendix, has also been collated into 2.5.1 Calculation of soil aggregate turnover in the revised manuscript.
In the Introduction section, we have (1) restructured the framework of the manuscript to make the manuscript more palatable to general readers; (2) outlined the major assumptions briefly; (3) deleted unnecessary description of the relationship between aggregate turnover and soil organic carbon dynamics to make the introduction section more relevant to the topic.
In the Material and method section, we have (1) introduced a more specific description of the Andisols soil samples in 2.1 Soil characteristics; （2）Changed the description of the experiment design in 2.3 Experiment design to make it more consistent with the research topic. (3) Added a flow chart of the recombination process in 2.3.1 Recombination process, to make the recombination process more accessible to the readers; (4) Added 2.5.1Calculation of soil aggregate turnover in the revised manuscript, from the original appendix and added Figure2 The 6 possible transformation pathways of aggregate.
In the Results section, we have (1) modified the structure of the result section according to the revised experiment design, and described the effect of the labeling and sieving process on aggregate turnover and organic carbon fractions, respectively; (2)added transformation aggregates turnover pathways before incubation (0 days) in 3.1.2 Soil aggregate turnover pathways; (3) Added soil organic carbon fraction dynamics of BG treatment during incubation in 3.2.2 The effect of labeling and sieving processes on SOC fractions during incubation process; (4) placed the relationship between aggregate turnover and organic carbon dynamics in 3.3 The effects on the quantitative study of the relationship between aggregate turnover and organic carbon dynamics.
In the Discussion section, we have reorganized the discussion according to the research topic and your comments. the impact of the labeling and sieving processes on soil aggregate turnover and soil organic carbon fractions were discussed, respectively.
In the Conclusion section, We have (1) identified that labeling and sieving processes could affect aggregate turnover and soil organic carbon fractions; (2) made suggestions for eliminating the disturbances.
Point to point response
Comment 1: Introduction, The introduction does not align well with the topic. The article aims to reveal the effects of labeling process and sieving method on aggregate turnover and soil C dynamics. However, in the introduction, related statements are rare, and the authors paid more attention to some unrelated points. For example, the soil types previous REOs studies has been used. Is the soil type (Andisols) very important? I do not think so. In my opinion, the authors should show us the shortage in REOs labeling studies (i.e., overlooks the effects of labeling process and sieving method) and its importance in assessing aggregate turnover dynamic and soil C dynamics, possible effects of labeling process and sieving method on aggregate turnover and soil C dynamics and how do them, and the potential relationships between aggregate turnover and soil C dynamics.
L39-42 why do you mention the concept of “humus”? does your study involve the chemical stability of SOM? the POM and HF you studied are fractioned by physical and density fraction method, not by acid or alkaline or thermal hydrolysis, right? Although they have different functions, they are commonly regarded from a perspective of physical stability/protection.
Reply1: We gratefully appreciate for your valuable comment. In the Introduction section, We have summarized comment1 as follows:
(1)The introduction does not fit the topic;
(2)Whether the soil type (Andisols) is important for the manuscript's results;
(3)Since 'humus' is not mentioned in the manuscript, the introduction to 'humus' should not be included in the introduction.
we have
(1)restructured introduction section from labeling and sieving processes on aggregate turnover and organic carbon dynamics, to make the introduction section more relevant to the research topic;
(2)added the explanation about the importance of soil types;
(3)deleted unnecessary description of the relationship between aggregate turnover and soil organic carbon dynamics;
Materials and methods
Comment 2: more details of the soil properties show be shown, such as SOC, soil texture and etcs.
Reply2: We gratefully appreciate for your valuable comment. We provide more soil properties in 2.1Soil characteristics in the revised manuscript. The soil properties were: bulk density:0.78g cm-3; soil pH: 6.50; total organic carbon (TOC): 53.21 mg g−1, total N: 4.54 mg g−1 , short range order mineral(SRO: allophane + ferrihydrite): 168 mg g−1; Sand (2.0–0.05 mm): 23.92%; Silt (0.05–0.002 mm): 31.02%; Clay (<0.002 mm): 45.06%.
Comment 3: L84-85: “soil sampled by a core at five random locations”. What’s the diameter of soil core? How large the region of soil sampling? Given that soil is highly heterogenous, how representative are the five cores?
Reply3: Thank you for your reminder. The diameter of the soil core is 5cm. The tillage site is a relatively smaller experimental field than normal farmland, the size of the experimental field is 22.5m*14m, and well organized by The National Agriculture and Food Research Organization, Japan. They carefully design and manage their experimental fields to avoid heterogeneity in the tillage layers. We ensured during our sampling that the thickness of the tillage layer was also nearly uniform. Wagai et al. (2013) and Asano and Wagai (2015) also used only six or five samples from the same experimental field. Following your comment, we added details about the experimental field in the revised manuscript.( 2.1 Soil characteristics).
Comment 4:
(1)L87: you separated three aggregate size classes (0.25-2, 0.053-0.25, <0.053mm), why there have four REOs? One is redundant?
(2)L95: I doubt that you can broke down to pass the soil through a 2-mm sieve just by hand without other tools after oven-dried. The wet-dry cycle of labeling process had clumped the soil.
(3)L114: how do you add the 13 ml of ultrapure water to avoid the rewet effect on aggregate turnover?
(4)L119-120: more details of the incubation. The top of box is open or close?
Reply4: We feel sorry for the inconvenience brought to the reviewer. In the previous manuscript, the REE oxides characteristic, labelling, sieving and incubation processes were all placed in 2.2 REO-labeled aggregates, resulting in a confusing and unreadable experimental design.
Therefore, based on comments, we have restructured the 2.3 experimental design section in revised manuscript, to bring it more consistent with the topic, and added more details to improve the reader's understanding.
(1)L87: you separated three aggregate size classes (0.25-2, 0.053-0.25, <0.053mm), why there have four REOs? One is redundant?
(1)We feel really sorry for our carelessness. Three REE oxides were selected as aggregate tracers, the 2-0.25 mm fraction labeled by Gd2O3 (A), 0.25-0.053 mm fraction labeled by Sm2O3 (B), and <0.053 mm fraction labeled by Nd2O3 (C). The REE oxides characteristics is described in2 REE oxides Characteristics.
(2)L95: I doubt that you can broke down to pass the soil through a 2-mm sieve just by hand without other tools after oven-dried. The wet-dry cycle of labeling process had clumped the soil.
(2)Thank you for your rigorous consideration. As much as the reviewer thinks so, there are many clods of soil that are difficult to break up by hand due to complete drying. Therefore, when the samples were dry and not sticky, the bulks were gently broken by hand with gloves. The details were added in 3.1 Labeling process.
(3)L114: how do you add the 13 ml of ultrapure water to avoid the rewet effect on aggregate turnover?
(3) We feel sorry that we did not provide enough information in the previous manuscript. we considered that the rewet effect on aggregate turnover may not need to be avoided. The transformation paths of three aggregate fractions were divided into (1) turnover directly caused by the labeling and sieving processes (at 0 days incubation); and (2) turnover caused by soil microorganisms during the incubation process (at 7,14,21,28 days incubation). The effect of the labeling, sieving and recombination processes on aggregate turnover was represented, by the turnover pathways of the aggregates at 0d in incubation. This section was described in 3 Experimental design.
(4)L119-120: more details of the incubation. The top of box is open or close?
(4) We gratefully appreciate for your valuable comment. Following your suggestion, more details about the incubation process were added in 2.3.4 Incubation process.
Comment 5:L175: where is the calculation of aggregate turnover rate? I can not find in the Appendix S1.
Reply5: We feel sorry for the inconvenience brought to the reviewer. In the revised manuscript, we have (1) introduced the calculation procedure in 2.5.1 Calculation of soil aggregate turnover; (2) inserted the schematic diagram of aggregate turnover, to make it easier for readers to understand.
Results
Comment 6: The authors showed lots of information in the text, without emphasizing the important information associated with the topic. For example, the effectivity of REOs labeling in tracing aggregate turnover has been widely proved, it is not an important information here. So, Fig.3 can be put in appendix rather than in text, and associated text should be more concise. Figs. 1 and 2 also can be merged.
Reply6: We gratefully appreciate for your valuable comment. Following your suggestion, we restructured the result section to incorporate 1) the effects of labelling, sieving and recombination processes (0d incubation) on organic matter; 2) the effects of labeling, sieving and recombination processes (0d incubation) on the distribution of agglomerates; 3) to verify the feasibility of REE oxides as tracers for Andisols; 4) the turnover pathways of aggregates during incubation; 5) the organic matter dynamics during incubation. This is actually the process of our experiment, not the validation of the research topic.
In the revised manuscript, to fit the research topic, we restructured the RESULT section as 1) The effect of labeling and sieving processes on Andisols aggregate turnover; 2) The effect of labeling and sieving processes on soil organic carbon fractions; 3) The effects on the quantitative study of the relationship between aggregate turnover and organic carbon dynamics. The modified Result section is as follows:
3.1The effect of labeling and sieving processes on Andisols aggregate turnover
3.1.1 verification of REE oxides as tracers of Andisols aggregate
3.1.2 Soil aggregate turnover pathways
3.2 The effect of labeling and sieving processes on soil organic carbon fractions
3.3 The effects on the quantitative study of the relationship between aggregate turnover and organic carbon dynamics.
In response to your question about the importance of the verification of the feasibility of using REE oxides as aggregate tracers, we hope to be able to provide an explanation. In previous studies we have found that REE oxides do not track 2-5mm fractions of Andisols very well during labeling (relevant manuscripts have been submitted and we hope that reviewers could continue to be interested in our studies). Therefore, in this study we needed to first ensure that REE oxides could be used as tracers to track Andisols <2mm fractions aggregate turnover, and then, use REE oxides to quantify aggregate turnover.
Comment 7: L194:why the format of Table 1 differs from other tables? And I feel uncomfortable with the unit in Table 1. g kg-1soil for TOC, fPOM, oPOM and HF and mg kg-1soil for MBC and DOC are more commonly used.
Reply7: Thank you so much for your careful check. As less attention has been paid to the effects of REE oxides addition, labelling, sieving and recombination processes on soil organic carbon in previous studies. Therefore, in this study, five treatments were designed as follows: (1) soil without REE oxides labeling and sieving processes (background treatment, BG), (2) soil with dry sieving and REE oxides labeling (REO-labeled and dry sieved treatment, REO-D), (3) soil with wet sieving and REE oxides labeling (REO-labeled and wet sieved treatment, REO-W), (4) soil with dry sieving but without REE oxides labeling (dry sieved treatment, CK-D), and (5) soil with wet sieving but without REE oxides labeling (wet sieved treatment, CK-W). Based on this design, we were able to determine the effect of REE oxides addition on the organic carbon fraction of soil aggregates by comparing the REO-D treatment with the CK-D treatment, the REO-W treatment with the CK-W treatment, and the effect of labeling and sieving processes on the organic matter fraction of the soil by comparing the BG treatment with other treatments.
Following your suggestion, g kg-1soil for TOC, fPOM, oPOM and HF and mg kg-1soil for MBC and DOC were used in Table3, and the relevant descriptions of the table were revised accordingly (3.2.1 The effect of labeling and sieving processes on soil organic carbon fractions after labeling and sieving processes).
Comment 8: Fig.7: Why do not show the absolute value of soil C fractions such as MBC and DOC? I think use the absolute value is more clearly than the proportions of them in SOC (the values are too low) to assess the effects of REOs labeling and sieving methods.
Reply 8: We feel sorry for the inconvenience brought to the reviewer. Following your suggestion, we have replaced the proportions of OC fractions in SOC with the absolute value in the figure and revised the description of the figures.
Discussion
Comment 9: I completely agree with the comments of another review about the discussion.
Besides, for section 4.3, authors paid more attention to discuss the aggregate turnover dynamics, where is the discussion of comparing the effects of labeling process and sieving method on aggregate turnover? I think it is the key point needing to be discussed.
Reply 9: We feel sorry for the inconvenience brought to the reviewer. We have tried too much to illustrate the feasibility of using soil organic carbon fractions and REE oxides to quantify soil organic carbon dynamics and soil aggregate turnover, respectively, and to analyze their relationship. This resulted in the Discussion section being inconsistent with the research topic.
(1)We discussed the effect of labeling and sieving processes on the aggregate turnover from 1)the feasibility of REE oxides as Andisols aggregate tracers; 2) The transformation of aggregate turnover pathways before incubation (0d); 3) The transformation of aggregate turnover pathways during incubation;4) the aggregate turnover rate during incubation(1 Effects of labeling and sieving processes on Andisols aggregate).
(2)We discussed the effects of the labeling and sieving process on soil organic carbon in terms of 1) the effect of wet sieving on soil organic carbon dynamics; 2) the effect of dry sieving on soil organic carbon dynamics(4.2 Effects of REE oxide labeling and sieving processes on soil organic carbon);
(3)We discussed the feasibility of using soil organic carbon fractions to analyze the relationship between organic carbon dynamics and aggregate turnover (Effects of the quantitative study of the relationship between aggregate turnover and organic carbon dynamics).
Comment 10: L334-338: explaining why wet sieving removes most fPOM. Does the dry sieving reduce fPOM because of the removal of fine roots and debris? The fine roots and debris should be removed before experiment, them were not pick out clean?
Reply 10: Thanks for your careful checks,we feel sorry that we did not provide enough information about dry sieving and wet sieving methods. The soil samples were root-picked prior to sieving, so both the wet and dry sieving treatments included fPOC loss from the root-picking process. However, during the wet sieving process, we found some free particulate organic matter floating on the water after sieving and this part of the POC was lost during the sieving process. Therefore, the fPOC of the wet sieving aggregates was significantly lower than that of the dry sieving aggregates and the BG treatment in this study.
Comment 11:
(1)Some problems of format at L345, 351, 361.
(2)L394-395: If the relationship between oPOM and aggregate fractions is important, please discuss it more in-depth, not just depict the result. If it is not important in this study, it is not necessary to show.
(3)L415: “The HF generated by aggregate breakdown cannot accumulate into aggregates, allowing it to accumulate on the outside and consequently increase the proportion of fPOM”, please attach the reference. I do not think the accumulation of HF can increase fPOM. They are varying in size, density and properties (e.g. C/N), two different concepts. The soil continuum model (Lehmann, J., Kleber, M., 2015. The contentious nature of soil organic matter. Nature 528: 60-68) suggested that fPOM can be degraded into HF with microbial processing, and it is an irreversible process.
Reply 11: It is really a giant mistake to the whole quality of our article. We feel sorry for our carelessness. We have corrected it and we also feel great thanks for your point out.Following the suggestion by you and the other anonymous reviewer, we removed the extensive discussion of the relationship between oPOM and aggregate fractions, and restructured the discussion in terms of labelling, sieving processes for 1) aggregate turnover; 2) organic matter dynamics; and 3) quantitative analysis of the relationship between organic matter and aggregates.
In response to L415: "The HF generated by aggregate breakdown cannot accumulate into aggregates, allowing it to accumulate on the outside and consequently increase the proportion of fPOM", not from other literature, but for the quantitative analysis of soil organic matter dynamics in relation to agglomerates during wet sieving, we found an increase in fPOC content and a decrease in oPOC and HF during incubation, and therefore feel that the increase in fPOC may be related to HF. The inaccurate description has been removed following your suggestion. The revised Discussion section is as supplement.
Conclusion
Comment 12: Do not simply repeat the results, but show the main findings and implications.
Reply 12: Thank you for your valuable suggestion.
Conclusions based on the research topic and discussion were obtained from aggregate turnover and soil organic carbon dynamics, respectively. The addition of REE oxides would have no effect on the Andisols aggregate turnover and organic carbon dynamics, but the REE oxides labeling and sieving processes would have effects on soil aggregates and soil organic carbon.
Acknowledgements
We gratefully thanks for the precious time the reviewer spent making constructive remarks.
Reference
Based on your suggestions, the Introduction and Discussion sections have been revised a lot, so we have restructured the Reference section.(8 Reference).
We hope you will find our revised manuscript acceptable for publication.
Yours sincerely,
Wang Yike
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AC3: 'Reply on RC2', Wang Yike, 03 Dec 2022
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