the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 29 Apr 2025
Availability of labile carbon controls the temperature-dependent response of soil organic matter decomposition in alpine soils
Abstract. Soil organic matter (SOM) decomposition in alpine environments is influenced by multiple factors including temperature and substrate quality. As climate change will have an impact on both factors, it is essential to improve our knowledge, how, e.g., warming will modify carbon cycling in these environments to better prepare soil management for future conditions, even in alpine regions. This study investigates how warming and organic inputs affect SOM decomposition in alpine forest and pasture soils through a one-year laboratory incubation experiment. Soils were exposed to three temperatures (12.5 °C, 16.5 °C and 20.5 °C), with and without the addition of fresh grass litter. While higher temperatures accelerated decomposition, the availability of fresh organic matter played a more decisive role, especially in the lignin-rich forest soil. Without fresh litter, SOM decomposition was limited, suggesting that substrate availability in combination with temperature increase plays a greater role in microbial activity than temperature alone. The forest soil exhibited greater carbon loss than the pasture soil, most likely due to microbial communities that are adapted to lignin decomposition. These results suggest that rising temperatures combined with changes in vegetation and organic inputs could enhance SOM decomposition and potentially transform the alpine soils from carbon sinks to sources.
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RC1: 'Comment on egusphere-2025-1546', Anonymous Referee #1, 30 May 2025
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AC1: 'Response to the comments of Anonymous Referee #1', Dario Püntener, 31 Jul 2025
We thank the reviewer for the thoughtful and constructive feedback on our manuscript. We appreciate the positive comments regarding the design, relevance and the novelty of our study. In response to the specific suggestions, we plan to revise the manuscript to improve clarity, conciseness and scientific precision. Below, we address each comment and outline the planned changes in the manuscript.
1) The discussion is long and would benefit from combining a couple related sections with more concise language.
We are grateful for this suggestion; we agree that the discussion is quite lengthy. We will combine some of the chapters to minimise repetition, especially chapters 4.1 and 4.2 as well as 4.3 and 4.4 can be better linked, as here the discussion was partially repetitive. A merge of the chapters will lead to easier reading.
2) The language in the discussion section about microbial communities differing should be revised to reflect the speculative nature of those comments, since the microbes themselves were not directly measured. For example, in L411, perhaps state "our results provide indirect evidence..."
We agree that statements about microbial communities should be framed more cautiously. We will revise the relevant sentences throughout the discussion to clearly reflect the indirect nature of our evidence.
3) The hypotheses should be reworded for clarity. One uses the word "potentially" twice, distracting from the main point. A hypothesis should be more direct.
Thanks a lot for this suggestion, we will reword the hypotheses, accordingly.
4) Are there any suggestions for future research needs, such as enzyme kinetics? Perhaps an explanation for the lack of temperature response without added litter? Have other studies examined microbial dynamics in these specific soils?
Enzyme kinetics might indeed be an interesting thing to look at, as they are often highly temperature sensitive, but the response to litter (labile C) availability is still unclear. So far, we did not investigate this, but we also conducted additional analysis of the incubated soils. We measured the concentration and C isotope composition of phospholipid fatty acids (PLFA) to gain insights into changes of microbial communities and the incorporation of the litter into the different microbial groups. This data will be included in another manuscript that is currently in preparation.
5) L14: reservoirs not reservoir
Thank you, this will be changed as suggested.
6) L28 "are discussed to be vulnerable" is awkward phrasing
Thank you, we agree and will change the phrasing in the revised hypotheses.
We hope these planned revisions address the raised concerns and we are sure that the planned changes will improve the overall quality and readability of the manuscript. We thank the reviewer again for the valuable insights.
Citation: https://doi.org/10.5194/egusphere-2025-1546-AC1
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AC1: 'Response to the comments of Anonymous Referee #1', Dario Püntener, 31 Jul 2025
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RC2: 'Comment on egusphere-2025-1546', Anonymous Referee #2, 16 Jun 2025
The manuscript addresses some very important issues. It presents the results of a well-designed laboratory experiment investigating the effect of warming on different fractions of soil organic matter. The manuscript is well written. The authors may wish to consider shortening some sections, as the manuscript as a whole is quite long.
L4 Abstract – why ‘even’?
The abstract is too general and should present more of the study's results.
L7-9 ‘Without fresh litter, SOM decomposition was limited, suggesting that substrate availability in combination with temperature increase plays a greater role in microbial activity than temperature alone.” This is obvious. Please be more precise and explain how big these effects were.
First paragraph of Introduction needs for more up-to-date references
L91 M&M 30 kg? This means that the sampling sites were quite close to the roads to enable the transportation of such a large sample. It may affect sampling sites (eutrophication, compaction etc.). Please discuss this issue
Table A1 – I'm not sure if this is necessary – the table is huge! However, I cannot find the Guide for Authors, so perhaps it is required or accepted by the publisher.
Citation: https://doi.org/10.5194/egusphere-2025-1546-RC2 -
AC2: 'Response to the comments of Anonymous Referee #2', Dario Püntener, 31 Jul 2025
We thank the reviewer for the thoughtful and constructive comments on our manuscript. We are pleased that they found the study to be well-designed, well-written, and relevant to pressing questions about soil C dynamics under warming. Below, we respond to each point in detail and outline the planned revisions to improve the manuscript.
1) The authors may wish to consider shortening some sections, as the manuscript as a whole is quite long.
We are grateful for this comment. We agree, especially the discussion seems to be lengthy. We will therefore combine some of the discussion chapters, i.e. 4.1. & 4.2 as well as 4.3 and 4.4 to reduce redundancy, emphasise important points more and thus also shorten the manuscript and improve the readability.
2) L4 Abstract – why ‘even’?
We agree, this doesn’t make sense, and we will remove the ‘even’ in the revised abstract.
3) The abstract is too general and should present more of the study's results.
We will revise the abstract to include more specific results. We will summarize the key quantitative findings, including temperature effects on TOC and differences in decomposition between soils with and without litter.
4) L7-9 ‘Without fresh litter, SOM decomposition was limited, suggesting that substrate availability in combination with temperature increase plays a greater role in microbial activity than temperature alone.” This is obvious. Please be more precise and explain how big these effects were.
We agree and will revise this sentence in the process of rewriting the abstract with more of the study’s result as also stated in comment 3.
5) First paragraph of Introduction needs for more up-to-date references
We appreciate this suggestion and will update the introduction with several recent references on SOM decomposition and warming impacts in alpine regions, e.g. Chen et al. (2024) Bright et al. (2025), Bonfanti et al. (2025). This will improve the contextual framing with newest scientific evidence and support the relevance of our study.
6) L91 M&M 30 kg? This means that the sampling sites were quite close to the roads to enable the transportation of such a large sample. It may affect sampling sites (eutrophication, compaction etc.). Please discuss this issue
We appreciate this critical observation. The, indeed, large samples were transported in several batches from soil pits to the small alpine path (no paved road), where samples were collected in a four-wheel drive vehicle. To minimize the effect of the road, we either sampled in a large distance above it (pasture) or at a site that was not influenced by the road (forest). We therefore think that any effect of the road was minimized by the careful site selection and the homogenization of the samples. However, we guess that such information is redundant in the M&M section and would exclude this, unless the reviewer or the editor see this as a crucial point that is worth it mentioning.
7) Table A1 – I'm not sure if this is necessary – the table is huge! However, I cannot find the Guide for Authors, so perhaps it is required or accepted by the publisher.
We thank the reviewer for raising this concern. Table A1 provides an overview of the incubation experiment parameters and the measured soil properties across all treatments and time points. This data supports key interpretations regarding litter-derived C incorporation and SOM decomposition dynamics. We believe this level of detail is important for transparency and reproducibility and therefore propose to retain Table A1 as Supplementary Material to avoid overloading the main manuscript. However, we are happy to follow editorial guidance if further reduction is advised.
We thank the reviewer again for their helpful feedback, which will strengthen the manuscript both scientifically and structurally. We believe the revisions will improve the manuscript’s precision, clarity and conciseness, and we hope it will meet the reviewer’s expectation for publication in SOIL.
References
Bright, K., Dienes, B., Keiluweit, M., Rixen, C. & Aeppli, M. Climate change impacts on organic carbon cycling in European alpine soils. Soil Biology and Biochemistry 210, 109891 (2025), https://doi.org/10.1016/j.soilbio.2025.109891
Bonfanti, N., Clément, J., Münkemüller, T., Barré, P., Baudin, F., Poulenard, J. Prolonged warming leads to carbon depletion and increases nutrient availability in alpine soils. Applied Soil Ecology 213, 106239 (2025). https://doi.org/10.1016/j.apsoil.2025.106239
Chen, C., Wang, L., Xia, W., Qiu, K., Guo, C., Gan, Z., Zhou, J., Sun, Y., Liu, D. Li, W. & Wang, T. Molecular interaction induced dual fibrils towards organic solar cells with certified efficiency over 20%. Nature Communications 15, 6865 (2024). https://doi.org/10.1038/s41467-024-51359-wCitation: https://doi.org/10.5194/egusphere-2025-1546-AC2
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AC2: 'Response to the comments of Anonymous Referee #2', Dario Püntener, 31 Jul 2025
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The study is well-conceived and has clear objectives, results, and conclusions. The temperature dependence of SOM decomposition in alpine soils has been well-studied for decades, but the novelty of this study's investigation of specific RCP temperature increases, with and without added labile litter, for specific alpine forest and grassland soils, makes the investigation worthwhile and of interest in an era of rapidly changing climate. A couple specific comments:
1) The discussion is long and would benefit from combining a couple related sections with more concise language.
2) The language in the discussion section about microbial communities differing should be revised to reflect the speculative nature of those comments, since the microbes themselves were not directly measured. For example, in L411, perhaps state "our results provide indirect evidence..."
3) The hypotheses should be reworded for clarity. One uses the word "potentially" twice, distracting from the main point. A hypothesis should be more direct.
4) Are there any suggestions for future research needs, such as enzyme kinetics? Perhaps an explanation for the lack of temperature response without added litter? Have other studies examined microbial dynamics in these specific soils?
5) L14: reservoirs not reservoir
6) L28 "are discussed to be vulnerable" is awkward phrasing