the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 08 Jan 2024
Diverse organic carbon dynamics captured by radiocarbon analysis of distinct compound classes in a grassland soil
Abstract. Soil organic carbon (SOC) is a large, dynamic reservoir composed of a complex mixture of plant and microbe derived compounds with a wide distribution of cycling timescales and mechanisms. The distinct residence times of individual C components within this reservoir depend on a combination of factors, including compound reactivity, mineral association, and climate conditions. To better constrain SOC dynamics, bulk radiocarbon measurements are commonly used to trace biosphere inputs into soils and estimate timescales of SOC cycling. However, understanding the mechanisms driving the persistence of organic compounds in bulk soil requires analyses of SOC pools that can be linked to plant sources and microbial transformation processes. Here, we adapt approaches, previously developed for marine sediments, to isolate organic compound classes from soils for radiocarbon (14C) analysis. We apply these methods to a soil profile from an annual grassland in Hopland, California (USA) to assess changes in SOC persistence with depth to 1 m. We measured the radiocarbon values of water extractable organic carbon (WEOC), total lipid extracts (TLE), total hydrolysable amino acids (AA), and an acid-insoluble (AI) fraction from bulk and physically separated size fractions (<2 mm, 2 mm–63 μm, and <63 μm). Our results show that Δ14C values of bulk soil, size fractions, and extracted compound classes became more depleted with depth, and individual SOC components have distinct age-depth distributions that suggest distinguishable cycling rates. We found that AA and TLE cycle faster than the bulk soils and the AI fraction. The AI was the most 14C depleted fraction, indicating it is the most chemically inert in this soil. Our approach enables the isolation and measurement of SOC fractions that separate functionally distinct SOC pools that can cycle relatively quickly (e.g., plant and microbial residues) from more passive or inert SOC pools (associated with minerals or petrogenic) from bulk soils and soil physical fractions. With the effort to move beyond SOC bulk analysis, we find that compound class 14C analysis can improve our understanding of SOC cycling and disentangle the physical and chemical factors driving OC cycling rates and persistence.
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The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
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The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
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Interactive discussion
Status: closed
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RC1: 'Comment on egusphere-2023-3125', Rienk Smittenberg, 18 Jan 2024
This paper by Grant et al presents a comprehensive study where they measured the 14C contents of many soil organic matter fractions with depth, from the specific grassland soil. These are very useful data to gain more insight in organic matter cycling in soils. A great amount of work lies behind it, for which I compliment the authors. Although the data are good, I think the paper would improve by a somewhat better presentation, and some more in depth discussions that can be structured better. I have given comments on the attached pdf, but some main and additional points here:
The influence of the bomb spike on 14C contents (especially important for the the upper layer) is missing in the discussion.
The authors discuss the relative differences between the various fractions (size, density, compound class), but not not discuss the depth aspect much, nor do they even try to quantify turnover times, which is one unique aspect that these 14C data allow. This is a missed chance.
A discussion of the source of the organic matter: besides leaf litter from above, which is then worked downwards by bioturbation and percolation, there should also be some root litter. Where does this go?
The structure of the discussion. This goes a little criss-cross through the data, size and compound fractions and I had to re-orient myself each time what figure and data to look at. One approach could be to try to answer certain questions/hypotheses using the data, and place this in perspective to data and insights from the literature. What is the most exciting news learned from this study?
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AC1: 'Reply on RC1', Katherine Grant, 31 May 2024
Thank you for your review and suggestions for improvements to the manuscript. In our revised manuscript, we will make all the requested grammatical, typographical, and clarification edits requested in the marked-up document and greatly appreciate your close reading of the manuscript. We also agree to add the density fractionation scheme from the supplemental file to Figure 1 of the main text and thank you for the suggestion. You also make several important points that we will address in the revision as we agree they will improve the manuscript.
- In our revised manuscript, we will make the suggested changes regarding the structure of the Discussion, which we agree will make the manuscript clearer and highlight the novelty of our data. The reviewer suggested formatting the Discussion using questions or hypothesis to improve the flow. For the revised Discussion, the first section will directly answer the question: “Are there difference in cycling time/age in the various compounds in the bulk soil? And how does this change with depth?” This section will include discussion of the compound classes in the “bulk” (<2mm) soils. This will introduce each compound class and discuss how they change by depth, which will address the reviewer’s suggestion to increase the discussion of depth effects. The second section of the discussion will address the question: “Do compound class cycling/age change between different “parent” fractions?” This section will focus on the size and density fractions, and we will be able to more logically progress the discussion of the “fast cycling pools” to the slower cycling pools. In addition, we will discuss the acid insoluble fraction (AI) earlier in the Discussion (in the first section) to improve the manuscript flow. We will clarify and expand upon the discussion of petrogenic carbon to include the idea that soil carbon is integrated into the larger rock fraction, which is evident in the higher D14C values found in the rock fraction even after cleaning with sonication and acid washing. We will specify that here we used the D14C values from the bulk soil fraction as the biospheric endmember. However, the total quantification of OCpetro is outside of the scope of this manuscript. We will also clarify that the term mineral-associated C that we refer to in this manuscript applies to both the silt/clay and the dense fraction, which we directly compare. We will also fix the error on lines 363-366 to read “it is still more 14C depleted at depth”.
- To address R1’s comment regarding the source of organic matter, we will specify in the site description that the site is annual grasses and shallow rooted herbs and forbs and that we did not observe roots below 10 cm. We point out when discussing the fast-cycling OC pool that litter and root inputs are limited to the surface soil in this shallow-rooted annual system.
- We also appreciate the suggestion to increase clarity with regards to which compounds are extracted from the different materials and will increase this specificity throughout the manuscript. In the revision, we will refer to the soil sample from which the extractions have been performed on as the “parent sample”. This will reduce confusion surrounding the nuanced terminology of the different compound extractions and physical fractions.
- We will add to the revised manuscript a short paragraph to under a new subheading “Interpretation of radiocarbon data” to introduce the influence of the bomb spike on 14C contents in the methods section We will provide a subheading. We agree that including this information earlier in the manuscript will improve the flow of the results and discussion. We will add the atmospheric 14C values for the time of sampling to this section as well as Figure 3, as requested. This will also help us in providing clearer discussion of depth trends within the profiles of the compounds (e.g., the incorporation of the bomb 14C in the upper layers and decline in 14C in very rapidly cycling pools following the decline in 14C toward pre-bomb values). This clarification will help the discussion of depth trends throughout the manuscript as requested.
- Finally, there is a comment regarding turnover time. We also thought this might help in our interpretation of our results and calculated turnover times using a one-pool steady state model following Sierra et al. (2014), Van Der Voort et al. (2019) and Torn et al. 2009. However, the presence of bomb 14C in shallow soil fractions and compound extracts resulted in two solutions that we were unable to resolve with only one time point. Thus, it remains unclear whether the turnover times were shorter or longer for lipids compared to amino acids. We could apply a multi-pool model (e.g., with Soil R) to our physical soil fractions, but are not yet confident in applying a multi-pool model structure to our compound classes and are further challenged by a lack of confidence in the proportional pool sizes (for example, we have not yet quantified carbohydrates and have considerable uncertainties regarding total soil C mass balance). We decided that for this manuscript, it was best to focus on the 14C data rather than apply a turnover time model that requires so many assumptions and is not well constrained. We do plan to pursue turnover or transit time modeling in the future as our work at Hopland and other sites is ongoing.
Citation: https://doi.org/10.5194/egusphere-2023-3125-AC1
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AC1: 'Reply on RC1', Katherine Grant, 31 May 2024
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RC2: 'Comment on egusphere-2023-3125', Anonymous Referee #2, 10 May 2024
In this manuscript, the authors describe radiocarbon data collected from a wide variety of soil carbon fractions following various definitional methods. This was done in an attempt to identify faster and slower cycling carbon pools following our understanding of bioavailability and persistence of soil carbon. The data are compelling and clearly presented, and the interpretation is well-founded. Thank you for the opportunity to review this research. This is a very strong manuscript that should be published following minor corrections.
Throughout the manuscript, there is some lack of narrative and propulsive sentence structure. The data here are novel and very important to the current understanding of soil carbon cycling, especially in the “mineral-associated/heavy” fraction and the diverse cycling rates therein. If these data can be presented in a stronger, more assertive fashion, these data could support a strong narrative. I may sound like a broken record on this, but it is the primary thing that could be improved on in an otherwise very strong manuscript. If the writing is tightened up and a bit more forward-leaning, this could be a high-impact paper.
Something that could possibly strengthen the discussion throughout is how “bulk soil” is referred to. Since we’re discussing radiocarbon, the “bulk soil” 14C is the mean of all C atoms in the soil. If an extracted C fraction is enriched, than it is cycling faster than the average C atom, or the average of the bulk soil. Of course, this is not a normal distribution. But if an extracted C pool has a higher radiocarbon content, that pool cycles more quickly than the soil C on average. Perhaps I haven’t articulated it well here either, but the framing of these C pools and being faster or slower than the mean i.e. bulk soil could support the narrative.
Below are line-by-line comments:
L43-50: I think this paragraph could better introduce why you want to specifically refer to compounds. I think a couple more references here and more active justification would serve this paragraph well.
L58-60: Switching this sentence to more active voice would clarify it and more strongly identify the persistent research question.
L70: The sentence that starts with “Each of these…” could better introduce these compounds as biologically valuable C pools, both of which we might assume to be quite fast-cycling. I think this sentence and the one on line 73 could add to the story of C decomposition in soil; a competition between microbial decomposition and stabilization, and the processes and soil characteristics that may determine those outcomes. I know this paragraph ends with a sentence along these lines, so maybe this could be reshuffled to create more narrative.
L73: I think there is something missing from this sentence; that, or the “not only” can be removed.
L81: “can be” is repeated.
L81: While “wholistic” is correct, “holistic” is more commonly used. Your choice.
L83: “of” is missing between “understanding” and “carbon”
L91: This probably was supposed to be “coastal”.
L246, 252: Add a + before positive radiocarbon values or remove them elsewhere, in the interest of consistency.
L272: “each of which” may flow better than just “which” on its own
L279-281: This sentence is doesn’t pack the punch that the last sentence of this first discussion paragraph could have to propel the discussion. Tie it in with the data directly, either why you see this, or why you don’t. This information is available from the figures, but it should be clear whether the data is behaving as you’d expect or otherwise.
L283: Maybe personal preference, but prepositions at the end of sentences should be avoided, “from which they were extracted”.
L284-285: This sentence could be tidied up to be easier to read and more propulsive.
L288: Maybe add “preferentially” here, to highlight that they are microbially active because of their N content making them more appealing
292-307: This is well reasoned, well done.
319: This is an great description of what WEOC is
L323: Maybe add “mobile” or something similar to this list
L324: Could this also be that the FLF fraction is the remainder of more “recalcitrant” C that persists after the more bioavailable C is decomposed (and possibly shows up in WEOC and POC)?
L326-328: These first two sentences could be streamlined for readability.
330-331: Why could this be the case? Due to closer contact with microbes and dissolved C under lower water conditions? Of course, if water content decreases enough then this could de facto preserve C as it cannot be accessed by microbes. Does this also imply abiotic oxidation? This sentence could be strengthened with one or two references and more context for why this observation would be expected.
332-335: Great!
350-351: This is true, but slightly redundant. What may be more interesting is that the sand size fraction is older (in order to produce a mean value in the bulk soil, if bulk – silt – clay = sand). We could assume the silt+clay to be more microbially active due to higher C content etc, and thus have enriched 14C, but the sand story is also interesting.
354-360: This is the first time AI is discussed, which is not inherently a problem but it is slightly jarring since the interpretation of AI data hasn’t been established yet.
363-366: What do you think is the source of the older TLE that is implied by the more depleted 14C in bulk soil TLE compared with DF TLE?
Upon looking at the figure, this may have been written incorrectly. It appears that DF TLE is always more depleted than bulk soil TLE except at the surface. This makes much more sense. One would not expect a source of older TLE in the FLF of OLF fractions, e.g. Be sure to correct this in the text.
I think this is a crucial paragraph, and is important in pushing our understanding of diverse, multi-level pools and highlights the benefits of compound-specific 14C analysis. Make sure it comes across with a strong statement.
379: The comma after “these” can be removed.
387: Indicative of aromatics
393-394: Interesting that the petrogenic rocks are still relatively modern. Do you think this a mixture of rock and more modern sources? Or rock-derived C being incorporated the biologic C cycle on the rock surface? There is some evidence of this occurring.
412-414: Good explanation.
415-425: Discussion of methodology limitations is often lacking, and this serves as a nice comparison of methodologies.
Section 4.5: If there is a recommendation to be made about size vs density separation, I think this is a good place to put it. Obviously there are pros and cons to each, but don’t shy away from suggesting one is better for research question X vs Y.
436: Abbreviate to SOC.
Citation: https://doi.org/10.5194/egusphere-2023-3125-RC2 -
AC2: 'Reply on RC2', Katherine Grant, 31 May 2024
Thank you for your review and suggestions for improvements to the manuscript. We agree with your comments and will make the minor edits suggested in the revision, including the additional references you’ve provided. You also make several important points that we will address in the revision as we agree they will improve the manuscript.
We will revise the language throughout the Introduction and Discussion to use stronger language reflecting the novelty of the data. Thank you very much for these comments and your enthusiasm for our work.
We agree that the language surrounding bulk soil in this manuscript and context was unclear. This was also brought up in R1. We have decided to refer to the “soil being extracted” as the “parent” sample, this terminology allows the direct tracing of which extraction came from which “original” parent fraction. We think this significantly clarifies the manuscript and helps reduce the confusion in terminology. Thank you for this helpful comment.
To respond to the specific comments: Thank you for the close reading of the MS, we have fixed all the grammatical errors and will incorporate more assertive language throughout, thank you very much for the helpful suggestions. We will add additional references where requested. We will reorder the paragraph in L70. These changes will greatly improve the manuscript. We will discuss the AI results earlier in the Discussion and fix the error on lines 363-366 to read “it is still more 14C depleted at depth”.
Citation: https://doi.org/10.5194/egusphere-2023-3125-AC2
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AC2: 'Reply on RC2', Katherine Grant, 31 May 2024
Interactive discussion
Status: closed
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RC1: 'Comment on egusphere-2023-3125', Rienk Smittenberg, 18 Jan 2024
This paper by Grant et al presents a comprehensive study where they measured the 14C contents of many soil organic matter fractions with depth, from the specific grassland soil. These are very useful data to gain more insight in organic matter cycling in soils. A great amount of work lies behind it, for which I compliment the authors. Although the data are good, I think the paper would improve by a somewhat better presentation, and some more in depth discussions that can be structured better. I have given comments on the attached pdf, but some main and additional points here:
The influence of the bomb spike on 14C contents (especially important for the the upper layer) is missing in the discussion.
The authors discuss the relative differences between the various fractions (size, density, compound class), but not not discuss the depth aspect much, nor do they even try to quantify turnover times, which is one unique aspect that these 14C data allow. This is a missed chance.
A discussion of the source of the organic matter: besides leaf litter from above, which is then worked downwards by bioturbation and percolation, there should also be some root litter. Where does this go?
The structure of the discussion. This goes a little criss-cross through the data, size and compound fractions and I had to re-orient myself each time what figure and data to look at. One approach could be to try to answer certain questions/hypotheses using the data, and place this in perspective to data and insights from the literature. What is the most exciting news learned from this study?
-
AC1: 'Reply on RC1', Katherine Grant, 31 May 2024
Thank you for your review and suggestions for improvements to the manuscript. In our revised manuscript, we will make all the requested grammatical, typographical, and clarification edits requested in the marked-up document and greatly appreciate your close reading of the manuscript. We also agree to add the density fractionation scheme from the supplemental file to Figure 1 of the main text and thank you for the suggestion. You also make several important points that we will address in the revision as we agree they will improve the manuscript.
- In our revised manuscript, we will make the suggested changes regarding the structure of the Discussion, which we agree will make the manuscript clearer and highlight the novelty of our data. The reviewer suggested formatting the Discussion using questions or hypothesis to improve the flow. For the revised Discussion, the first section will directly answer the question: “Are there difference in cycling time/age in the various compounds in the bulk soil? And how does this change with depth?” This section will include discussion of the compound classes in the “bulk” (<2mm) soils. This will introduce each compound class and discuss how they change by depth, which will address the reviewer’s suggestion to increase the discussion of depth effects. The second section of the discussion will address the question: “Do compound class cycling/age change between different “parent” fractions?” This section will focus on the size and density fractions, and we will be able to more logically progress the discussion of the “fast cycling pools” to the slower cycling pools. In addition, we will discuss the acid insoluble fraction (AI) earlier in the Discussion (in the first section) to improve the manuscript flow. We will clarify and expand upon the discussion of petrogenic carbon to include the idea that soil carbon is integrated into the larger rock fraction, which is evident in the higher D14C values found in the rock fraction even after cleaning with sonication and acid washing. We will specify that here we used the D14C values from the bulk soil fraction as the biospheric endmember. However, the total quantification of OCpetro is outside of the scope of this manuscript. We will also clarify that the term mineral-associated C that we refer to in this manuscript applies to both the silt/clay and the dense fraction, which we directly compare. We will also fix the error on lines 363-366 to read “it is still more 14C depleted at depth”.
- To address R1’s comment regarding the source of organic matter, we will specify in the site description that the site is annual grasses and shallow rooted herbs and forbs and that we did not observe roots below 10 cm. We point out when discussing the fast-cycling OC pool that litter and root inputs are limited to the surface soil in this shallow-rooted annual system.
- We also appreciate the suggestion to increase clarity with regards to which compounds are extracted from the different materials and will increase this specificity throughout the manuscript. In the revision, we will refer to the soil sample from which the extractions have been performed on as the “parent sample”. This will reduce confusion surrounding the nuanced terminology of the different compound extractions and physical fractions.
- We will add to the revised manuscript a short paragraph to under a new subheading “Interpretation of radiocarbon data” to introduce the influence of the bomb spike on 14C contents in the methods section We will provide a subheading. We agree that including this information earlier in the manuscript will improve the flow of the results and discussion. We will add the atmospheric 14C values for the time of sampling to this section as well as Figure 3, as requested. This will also help us in providing clearer discussion of depth trends within the profiles of the compounds (e.g., the incorporation of the bomb 14C in the upper layers and decline in 14C in very rapidly cycling pools following the decline in 14C toward pre-bomb values). This clarification will help the discussion of depth trends throughout the manuscript as requested.
- Finally, there is a comment regarding turnover time. We also thought this might help in our interpretation of our results and calculated turnover times using a one-pool steady state model following Sierra et al. (2014), Van Der Voort et al. (2019) and Torn et al. 2009. However, the presence of bomb 14C in shallow soil fractions and compound extracts resulted in two solutions that we were unable to resolve with only one time point. Thus, it remains unclear whether the turnover times were shorter or longer for lipids compared to amino acids. We could apply a multi-pool model (e.g., with Soil R) to our physical soil fractions, but are not yet confident in applying a multi-pool model structure to our compound classes and are further challenged by a lack of confidence in the proportional pool sizes (for example, we have not yet quantified carbohydrates and have considerable uncertainties regarding total soil C mass balance). We decided that for this manuscript, it was best to focus on the 14C data rather than apply a turnover time model that requires so many assumptions and is not well constrained. We do plan to pursue turnover or transit time modeling in the future as our work at Hopland and other sites is ongoing.
Citation: https://doi.org/10.5194/egusphere-2023-3125-AC1
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AC1: 'Reply on RC1', Katherine Grant, 31 May 2024
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RC2: 'Comment on egusphere-2023-3125', Anonymous Referee #2, 10 May 2024
In this manuscript, the authors describe radiocarbon data collected from a wide variety of soil carbon fractions following various definitional methods. This was done in an attempt to identify faster and slower cycling carbon pools following our understanding of bioavailability and persistence of soil carbon. The data are compelling and clearly presented, and the interpretation is well-founded. Thank you for the opportunity to review this research. This is a very strong manuscript that should be published following minor corrections.
Throughout the manuscript, there is some lack of narrative and propulsive sentence structure. The data here are novel and very important to the current understanding of soil carbon cycling, especially in the “mineral-associated/heavy” fraction and the diverse cycling rates therein. If these data can be presented in a stronger, more assertive fashion, these data could support a strong narrative. I may sound like a broken record on this, but it is the primary thing that could be improved on in an otherwise very strong manuscript. If the writing is tightened up and a bit more forward-leaning, this could be a high-impact paper.
Something that could possibly strengthen the discussion throughout is how “bulk soil” is referred to. Since we’re discussing radiocarbon, the “bulk soil” 14C is the mean of all C atoms in the soil. If an extracted C fraction is enriched, than it is cycling faster than the average C atom, or the average of the bulk soil. Of course, this is not a normal distribution. But if an extracted C pool has a higher radiocarbon content, that pool cycles more quickly than the soil C on average. Perhaps I haven’t articulated it well here either, but the framing of these C pools and being faster or slower than the mean i.e. bulk soil could support the narrative.
Below are line-by-line comments:
L43-50: I think this paragraph could better introduce why you want to specifically refer to compounds. I think a couple more references here and more active justification would serve this paragraph well.
L58-60: Switching this sentence to more active voice would clarify it and more strongly identify the persistent research question.
L70: The sentence that starts with “Each of these…” could better introduce these compounds as biologically valuable C pools, both of which we might assume to be quite fast-cycling. I think this sentence and the one on line 73 could add to the story of C decomposition in soil; a competition between microbial decomposition and stabilization, and the processes and soil characteristics that may determine those outcomes. I know this paragraph ends with a sentence along these lines, so maybe this could be reshuffled to create more narrative.
L73: I think there is something missing from this sentence; that, or the “not only” can be removed.
L81: “can be” is repeated.
L81: While “wholistic” is correct, “holistic” is more commonly used. Your choice.
L83: “of” is missing between “understanding” and “carbon”
L91: This probably was supposed to be “coastal”.
L246, 252: Add a + before positive radiocarbon values or remove them elsewhere, in the interest of consistency.
L272: “each of which” may flow better than just “which” on its own
L279-281: This sentence is doesn’t pack the punch that the last sentence of this first discussion paragraph could have to propel the discussion. Tie it in with the data directly, either why you see this, or why you don’t. This information is available from the figures, but it should be clear whether the data is behaving as you’d expect or otherwise.
L283: Maybe personal preference, but prepositions at the end of sentences should be avoided, “from which they were extracted”.
L284-285: This sentence could be tidied up to be easier to read and more propulsive.
L288: Maybe add “preferentially” here, to highlight that they are microbially active because of their N content making them more appealing
292-307: This is well reasoned, well done.
319: This is an great description of what WEOC is
L323: Maybe add “mobile” or something similar to this list
L324: Could this also be that the FLF fraction is the remainder of more “recalcitrant” C that persists after the more bioavailable C is decomposed (and possibly shows up in WEOC and POC)?
L326-328: These first two sentences could be streamlined for readability.
330-331: Why could this be the case? Due to closer contact with microbes and dissolved C under lower water conditions? Of course, if water content decreases enough then this could de facto preserve C as it cannot be accessed by microbes. Does this also imply abiotic oxidation? This sentence could be strengthened with one or two references and more context for why this observation would be expected.
332-335: Great!
350-351: This is true, but slightly redundant. What may be more interesting is that the sand size fraction is older (in order to produce a mean value in the bulk soil, if bulk – silt – clay = sand). We could assume the silt+clay to be more microbially active due to higher C content etc, and thus have enriched 14C, but the sand story is also interesting.
354-360: This is the first time AI is discussed, which is not inherently a problem but it is slightly jarring since the interpretation of AI data hasn’t been established yet.
363-366: What do you think is the source of the older TLE that is implied by the more depleted 14C in bulk soil TLE compared with DF TLE?
Upon looking at the figure, this may have been written incorrectly. It appears that DF TLE is always more depleted than bulk soil TLE except at the surface. This makes much more sense. One would not expect a source of older TLE in the FLF of OLF fractions, e.g. Be sure to correct this in the text.
I think this is a crucial paragraph, and is important in pushing our understanding of diverse, multi-level pools and highlights the benefits of compound-specific 14C analysis. Make sure it comes across with a strong statement.
379: The comma after “these” can be removed.
387: Indicative of aromatics
393-394: Interesting that the petrogenic rocks are still relatively modern. Do you think this a mixture of rock and more modern sources? Or rock-derived C being incorporated the biologic C cycle on the rock surface? There is some evidence of this occurring.
412-414: Good explanation.
415-425: Discussion of methodology limitations is often lacking, and this serves as a nice comparison of methodologies.
Section 4.5: If there is a recommendation to be made about size vs density separation, I think this is a good place to put it. Obviously there are pros and cons to each, but don’t shy away from suggesting one is better for research question X vs Y.
436: Abbreviate to SOC.
Citation: https://doi.org/10.5194/egusphere-2023-3125-RC2 -
AC2: 'Reply on RC2', Katherine Grant, 31 May 2024
Thank you for your review and suggestions for improvements to the manuscript. We agree with your comments and will make the minor edits suggested in the revision, including the additional references you’ve provided. You also make several important points that we will address in the revision as we agree they will improve the manuscript.
We will revise the language throughout the Introduction and Discussion to use stronger language reflecting the novelty of the data. Thank you very much for these comments and your enthusiasm for our work.
We agree that the language surrounding bulk soil in this manuscript and context was unclear. This was also brought up in R1. We have decided to refer to the “soil being extracted” as the “parent” sample, this terminology allows the direct tracing of which extraction came from which “original” parent fraction. We think this significantly clarifies the manuscript and helps reduce the confusion in terminology. Thank you for this helpful comment.
To respond to the specific comments: Thank you for the close reading of the MS, we have fixed all the grammatical errors and will incorporate more assertive language throughout, thank you very much for the helpful suggestions. We will add additional references where requested. We will reorder the paragraph in L70. These changes will greatly improve the manuscript. We will discuss the AI results earlier in the Discussion and fix the error on lines 363-366 to read “it is still more 14C depleted at depth”.
Citation: https://doi.org/10.5194/egusphere-2023-3125-AC2
-
AC2: 'Reply on RC2', Katherine Grant, 31 May 2024
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