I have received three reviews of the manuscript, of which two were quite positive and one was extremely negative. My own reading lies somewhere between these poles. I think with attention to the comments of the reviewers the authors will be able to produce an acceptable contribution.

The goal of the manuscript is to assess different methods to determine current mineral weathering rates in soils. The question is of more than academic importance, as mineral weathering must in the long run replace cation loss resulting from forest harvesting and consequent soil acidification. The work is conducted in the context of a Swedish environmental goal of managing sustainable forestry. Three established methods of assessing weathering rates are tested in two well-characterized forest soils in Sweden. While the work is clearly important from this perspective, the question and the methods used are not an approach that is likely to bring about a paradigm shift or blinding insight.

Reviewer #1 offered the very negative appraisal, based mostly on two points—first that the methods and models used have been compared in other sites before, and therefore there is nothing new. The second complaint was that little data was used from the two study sites. I sympathize with the authors response that this study is distinguished from others by the quality of the data available for the method comparison (a key being uniformity of collection and analysis methods). Both negative points can be addressed with nearly the same antidote: providing a much clearer description of how the data used is generated. I suggest the authors come up with a way to highlight responses to this reviewer very early and with some panache in the text. The text is rather long overall, and while methodical in its presentation, it is easy to miss the point amidst some of the details.

General points to attend from Reviewers 2 & 3:
1) Terminology: Reviewer #2 found the manuscript very interesting, but also offers some helpful guidance on improving clarity. I concur with this reviewer that the terminology naming the methods was hard to keep straight. In short, these are “depletion method”, the “steady-state method”, and the “mass balance method”. For instance, the depletion method (based on the assumption of Zr immobility) is in essence a mass balance calculation. I wonder if the authors could come up with a small table that would summarize the 3 methods? It would be helpful to have these briefly outlined and set apart from the text in a way that the reader can circle back quickly when confusion sets in.

I believe some terminological confusion arises because the goals of this study are narrowly focused on determining the weathering rate going on in Swedish forests now, to address the needs of forest management now. Some of the methods employed (depletion method in particular) are averaged over much longer timescale than the present (more on this below). Moreover, choices such as focusing only on the top 50 cm are driven by interest in weathering in the rooting zone. I think the authors might rewrite the introduction and parts of the discussion to highlight how their motivations might differ from those of a pedologist, interested in the full history and depth of soil development, or from a geochemist interested in weathering rates over long time scales.

2) Soil age: I disagree with Reviewer #2 on soil age changing with depth in the soil profile. It is standard soil science to use soil age in the manner used by the authors. However, the authors need to correct an error in their reporting of soil ages. Asa is reported to be 143 000 thousand years old (or 1.43 x 10^8 years…. Cretaceous!), while Flakaliden is reported as 10 150 thousand (1.015 x 10^7 years). I’m pretty sure the authors mean 143 ka and 10.15 ka, respectively. These ages are significantly different. Asa has been exposed and weathering since the last interglacial, while Flakaliden is only Holocene. The significant difference in weathering (disintegration of boulders, accumulations of clay and organic matter, etc) in till from different glaciations is an important tool in determining relative ages. I am surprised that the influence of the much longer pedogenesis at the Asa site is not addressed in the manuscript. Since Asa was apparently not glaciated in the last glaciation, I would guess it was instead subjected to periglacial processes for ~100 ka of its age. I also wonder about any eolian (e.g. loess) deposition during the last glaciation? In any case, I would like the authors to address the very different history of weathering at these sites and how this impacts the weathering rates they assess. (In line 218-219, the soils are described as similar in B horizon thickness-- quite surprising given the 1000 fold difference in age of these soils that the B horizons are similar in thickness. You will need to explain why-- it's striking that the very old soil in the warmer climate seems to be quite similar to the very young soil in the colder climate.)

3) Table 4 “quality of term quantification”. Several reviewers were unimpressed with a vague and subjective description of the quality of quantification of different terms in the mass balance method. Is there a better way to do this?

Reviewer #2 offers a number of useful comments on minor points in the manuscript, please address these.

4) I found the Conclusions section to be unsatisfying. As the 11th group to compare different weathering rate computation methods, is our knowledge of weathering rates improved? Did using more carefully collected data and uniform sampling methods improve these numbers? I am not sure from reading the conclusions. Nor am I sure what recommendation would be made to land managers on the basis of this work for how to measure weathering rates. I suggest pulling back out to the big picture, and addressing the reader who has skipped from introduction straight to conclusions in rewriting this section.

My own minor comments:
Line 65: The definition of “weathering rate” given does not define a rate (dimensionally).
Line 182: I’m surprised at lack of attention to till mineralogy: does this differ between sites?
Line 200: Describe the solid fertilizer used.
Line 218: “sandy loam till” is not a texture. “sandy loam” is.
Line 607-608: Pinus is conifer, not deciduous. What was the vegetation at Asa during the last glaciation?

I have received three reviews of the manuscript, of which two were quite positive and one was extremely negative. My own reading lies somewhere between these poles. I think with attention to the comments of the reviewers the authors will be able to produce an acceptable contribution.

The goal of the manuscript is to assess different methods to determine current mineral weathering rates in soils. The question is of more than academic importance, as mineral weathering must in the long run replace cation loss resulting from forest harvesting and consequent soil acidification. The work is conducted in the context of a Swedish environmental goal of managing sustainable forestry. Three established methods of assessing weathering rates are tested in two well-characterized forest soils in Sweden. While the work is clearly important from this perspective, the question and the methods used are not an approach that is likely to bring about a paradigm shift or blinding insight.

Reviewer #1 offered the very negative appraisal, based mostly on two points—first that the methods and models used have been compared in other sites before, and therefore there is nothing new. The second complaint was that little data was used from the two study sites. I sympathize with the authors response that this study is distinguished from others by the quality of the data available for the method comparison (a key being uniformity of collection and analysis methods). Both negative points can be addressed with nearly the same antidote: providing a much clearer description of how the data used is generated. I suggest the authors come up with a way to highlight responses to this reviewer very early and with some panache in the text. The text is rather long overall, and while methodical in its presentation, it is easy to miss the point amidst some of the details.

General points to attend from Reviewers 2 & 3:
1) Terminology: Reviewer #2 found the manuscript very interesting, but also offers some helpful guidance on improving clarity. I concur with this reviewer that the terminology naming the methods was hard to keep straight. In short, these are “depletion method”, the “steady-state method”, and the “mass balance method”. For instance, the depletion method (based on the assumption of Zr immobility) is in essence a mass balance calculation. I wonder if the authors could come up with a small table that would summarize the 3 methods? It would be helpful to have these briefly outlined and set apart from the text in a way that the reader can circle back quickly when confusion sets in.

I believe some terminological confusion arises because the goals of this study are narrowly focused on determining the weathering rate going on in Swedish forests now, to address the needs of forest management now. Some of the methods employed (depletion method in particular) are averaged over much longer timescale than the present (more on this below). Moreover, choices such as focusing only on the top 50 cm are driven by interest in weathering in the rooting zone. I think the authors might rewrite the introduction and parts of the discussion to highlight how their motivations might differ from those of a pedologist, interested in the full history and depth of soil development, or from a geochemist interested in weathering rates over long time scales.

2) Soil age: I disagree with Reviewer #2 on soil age changing with depth in the soil profile. It is standard soil science to use soil age in the manner used by the authors. However, the authors need to correct an error in their reporting of soil ages. Asa is reported to be 143 000 thousand years old (or 1.43 x 10^8 years…. Cretaceous!), while Flakaliden is reported as 10 150 thousand (1.015 x 10^7 years). I’m pretty sure the authors mean 143 ka and 10.15 ka, respectively. These ages are significantly different. Asa has been exposed and weathering since the last interglacial, while Flakaliden is only Holocene. The significant difference in weathering (disintegration of boulders, accumulations of clay and organic matter, etc) in till from different glaciations is an important tool in determining relative ages. I am surprised that the influence of the much longer pedogenesis at the Asa site is not addressed in the manuscript. Since Asa was apparently not glaciated in the last glaciation, I would guess it was instead subjected to periglacial processes for ~100 ka of its age. I also wonder about any eolian (e.g. loess) deposition during the last glaciation? In any case, I would like the authors to address the very different history of weathering at these sites and how this impacts the weathering rates they assess. (In line 218-219, the soils are described as similar in B horizon thickness-- quite surprising given the 1000 fold difference in age of these soils that the B horizons are similar in thickness. You will need to explain why-- it's striking that the very old soil in the warmer climate seems to be quite similar to the very young soil in the colder climate.)

3) Table 4 “quality of term quantification”. Several reviewers were unimpressed with a vague and subjective description of the quality of quantification of different terms in the mass balance method. Is there a better way to do this?

Reviewer #2 offers a number of useful comments on minor points in the manuscript, please address these.

4) I found the Conclusions section to be unsatisfying. As the 11th group to compare different weathering rate computation methods, is our knowledge of weathering rates improved? Did using more carefully collected data and uniform sampling methods improve these numbers? I am not sure from reading the conclusions. Nor am I sure what recommendation would be made to land managers on the basis of this work for how to measure weathering rates. I suggest pulling back out to the big picture, and addressing the reader who has skipped from introduction straight to conclusions in rewriting this section.

My own minor comments:
Line 65: The definition of “weathering rate” given does not define a rate (dimensionally).
Line 182: I’m surprised at lack of attention to till mineralogy: does this differ between sites?
Line 200: Describe the solid fertilizer used.
Line 218: “sandy loam till” is not a texture. “sandy loam” is.
Line 607-608: Pinus is conifer, not deciduous. What was the vegetation at Asa during the last glaciation?

Please read the latest referee reports, particularly Referee #4 and #5, for guidance on your revisions. The need to clearly state the goals of the manuscript in the Introduction, and describe the contributions toward these goals in the Summary was noted in the previous round of review. Referee #5 emphasizes (in points 20 and 21 of his review) that solving this problem is essential for this manuscript to be ready for an international audience-- i.e. for a community outside of Swedish forestry. Correcting this problem should be your highest priority in your revision.

Please correct the problems with numbering of tables and figures, particularly in the Supplement. Provide Figure captions for all figures, including the Supplement. Heed requests for unit labeling on figures.

Please use consistent terminology throughout the manuscript, figures and tables for each of the three weathering rate methods employed.

Referee #5 notes some under-referencing of the literature that should be attended to.

Dear Authors,

The reviewers have reported that the manuscript has substantially been revised, and it has reached the acceptable level for the publication in Biogeosciences.
Please follow the suggestions from the editorial office to make the final version.

Best,

Nobuhito Ohte. Handling Editor