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Open AccessArticle

Peer-Review Record

The Contribution of Coniferous Canopy to the Molecular Diversity of Dissolved Organic Matter in Rainfall

Reviewer 1: Anonymous
Reviewer 2: Anonymous
Reviewer 3: Anonymous
Reviewer 4: Tiina M. Nieminen
Water 2019, 11(1), 167; https://doi.org/10.3390/w11010167
Received: 10 December 2018 / Revised: 15 January 2019 / Accepted: 16 January 2019 / Published: 18 January 2019
(This article belongs to the Section Water Quality and Ecosystems)

Round 1

Reviewer 1 Report

General comments :

Up to now, there are only few studies in the world that have investigated the molecular composition of different types of water fluxes in forests compared to incoming rainwater. The present manuscript is a case study (1 site, 1 plantation, 1 rain event). Nonetheless, it provides insights into this question for Chamaecyparis obtusa plantation in Japan. The manuscript is well-structured and easy to read. The introduction provides sufficient background. I would, however, ask the authors to detail a bit more  the introduction regarding the water conservation role of forests. As is now, the wording is vague. Specifically, do the authors mean water quality and/or quantity conservation thanks to forests ? Also, please go into the conservation implications of highly diverse water inputs via throughfall to the forest soils compare to rainwater in open areas. Furthermore, the results are well presented and figures are clearly explained. The discussion is a bit short. I would ask the authors to discuss their results in the context of water conservation under forests. Also, I would like to see in the discussion comments from the authors about their expectations of how their results would look like if several events were sampled in several plantations of different tree species in Japan. Do they think that the results of their case study can be generalized to a larger region/differ tree species in Japan ?

 

Specific comments :

Line 37 : On the other hand is not necessary.

Lines 37-41 : This paragraph refers to the situation in Japan. I assume so due to sole reference to citations 1 and 2. If so, then why do the authors not state upfront in the introduction that studies are crucially needed in Japan to investigate and develop measures for forests goods and services (here water conservation).

Lines 49-50 : There is no « on the one hand » before. I thus suggest rephrasing « when rainfall come sinto contact with tree canopies in forest ecosystems, it changes the quality of … »

Line 53 : Do you mean water quality conservation ?

Lines 53 : How large is the amount of DOM in the references cited ? Please state a range of values and in which ecosystems they were found.

Lines 81-85 : Could you provide more information about the plantation in terms of productivity and structure (e.g. basal area, tree height, LAI) ?

Lines 112-113 : Why was it decided to look at m/z range 180-500 ? Did you find larger molecules than 500 ?

Lines 131 : what were the R packages used ?

Line 183 : « DOM molecules in throughfall and stemflow… »

Lines 185-193 : what does this mean in terms of implication for water quality and the conservation role of forests/plantations of Japanese cypress ? Since the DOC flux and the number of m/z are higher in TF than RF, what can you infer, using literature, about the fate of the increased inputs of lipids, proteins (N input) and lignins/tannins from TF to forest soils ?

Line 193 : « dissolves and leaches plant-derived molecular species ».


Author Response

We greatly appreciate the reviewer's positive comments and suggestions, which have been helpful for our revision.

 

General comments:

 

Reviewer's comment:

Up to now, there are only few studies in the world that have investigated the molecular composition of different types of water fluxes in forests compared to incoming rainwater. The present manuscript is a case study (1 site, 1 plantation, 1 rain event). Nonetheless, it provides insights into this question for Chamaecyparis obtusa plantation in Japan. The manuscript is well structured and easy to read. The introduction provides sufficient background.

I would, however, ask the authors to detail a bit more the introduction regarding the water conservation role of forests. As is now, the wording is vague. Specifically, do the authors mean water quality and/or quantity conservation thanks to forests?

Also, please go into the conservation implications of highly diverse water inputs via throughfall to the forest soils compare to rainwater in open areas.

Furthermore, the results are well presented and figures are clearly explained. The discussion is a bit short. I would ask the authors to discuss their results in the context of water conservation under forests.

Also, I would like to see in the discussion comments from the authors about their expectations of how their results would look like if several events were sampled in several plantations of different tree species in Japan. Do they think that the results of their case study can be generalized to a larger region/differ tree species in Japan ?

 

Authors' comment:

Based on the comment, in the Introduction section, we added the description that forests influence water availability and regulate surface and groundwater flows while maintaining water quality, via interactions between rainwater and forest elements, e.g., trees, litter, and soils (Lines 40–42). We could not provide clear insights about the water conservation function of forests based on our data obtained from FT-ICR MS. However, in the Discussion section, we added the description that the readily mineralisable DOM molecules, such as proteins, were provided from tree leaves to the forest floor via throughfall, which in turn can stimulate microbial activities related to changes in water chemistry (Lines 204–208).

This study presented the results of DOM molecules obtained during one rain event. However, rainfall amounts can affect the number of DOM molecules in throughfall because some other studies have shown that rainfall amounts increased the throughfall DOC flux via wash-off of dry deposits from the tree canopy and leaching from the plant tissues. Therefore, further studies are needed on inter-event variations in DOM molecular species in throuhfall to generalize our indication that the tree canopy can add a diverse array of DOM molecules to rainwater in a Japanese cypress plantation. We added these descriptions in Lines 217–230. We also added the description that molecular species of DOM in throughfall can greatly vary depending on tree species, because Stubbins et al. (2017) showed that molecular species of throughfall DOM were explicitly separated between oak and cedar stands in subtropical forests in the USA (Lines 211–216). Therefore, in expanding our results to a larger scale, such as watershed scale, the composition of tree species within a watershed should be considered. However, we did not add discussion about expanding our results to a larger scale, because it strays from the main topic of this study and we do not have any available data to examine it.

 

Specific comments :

 

Reviewer's comment:

Line 37 : On the other hand is not necessary.


Authors' comment:

In accordance with, we deleted "On the other hand".

 

Reviewer's comment:

Lines 37-41 : This paragraph refers to the situation in Japan. I assume so due to sole reference to citations 1 and 2. If so, then why do the authors not state upfront in the introduction that studies are crucially needed in Japan to investigate and develop measures for forests goods and services (here water conservation).

 

Authors' comment:

As described earlier, we added the sentence, “Particularly, forests play central roles in water availability and in regulating surface and groundwater flows while maintaining water chemistry, via interactions between rainwater and forest elements, such as, trees, litter, and soils” in the Introduction Lines 40–42. Then, based on the comment, we added the description that studies are needed to develop measures for evaluating the water conservation function of forests, by changing "multi-functional roles" to "water conservation function" in Lines 43.

 

Reviewer's comment:

Lines 49-50 : There is no « on the one hand » before. I thus suggest rephrasing « when rainfall come sinto contact with tree canopies in forest ecosystems, it changes the quality of … »

 

Authors' comment:

In accordance with the comment, I deleted “On the other hand”. I also revised the sentence, "rainfall comes into contact with tree canopies in forest ecosystems, which greatly changes the quality of rainwater ..." to "When rainfall comes into contact with tree canopies in forest ecosystems, the quality of rainwater greatly changes ..." (Lines 53–54).

 

Reviewer's comment:

Line 53 : Do you mean water quality conservation ?

 

Authors' comment:

In accordance with the comment, I revised "water conservation" to "water quality conservation" (Line 56).

 

Reviewer's comment:

Lines 53 : How large is the amount of DOM in the references cited ? Please state a range of values and in which ecosystems they were found.

 

Authors' comment:

Based on the comment, we added the sentence, "Schrumpf et al.[14] showed that annual fluxes of dissolved organic carbon (DOC) in rainfall (59–144 kg ha^–1) increased to 142–219 kg ha^–1 during the passage through the forest covers in a montane rainforest" in Lines 57–59. We also changed the cited literature, Quall and Haines (1992) to Qualls et al (1991) in Line 57. Because this addition, we changed "dissolved organic carbon concentrations" to "DOC concentrations" in Line 60.

 

Reviewer's comment:

Lines 81-85 : Could you provide more information about the plantation in terms of productivity and structure (e.g. basal area, tree height, LAI) ?

 

Authors' comment:

In accordance with the comment, we added information about tree height and diameter at breast height.

 

Reviewer's comment:

Lines 112-113 : Why was it decided to look at m/z range 180-500 ? Did you find larger molecules than 500 ?

 

Authors' comment:

This is because we tried to compare our data with the results of Ide et al. (2017), which applied FT-ICR MS to rainwater moving through a forest for the first time in the world, under the similar condition of the FT-ICR mass spectrometer. Besides, several studies have shown that ions exceeding m/z 800 are hardly found in mass spectra of natural organic matter detected by ESI coupled to mass spectrometry and that intensity maxima occur in the range of m/z 350–500 (Reemtsma 2009). Indeed, there were little m/z peaks in the mass spectra of exceeding m/z 500 as shown in the supporting material (Figures S2 and S3). From these reasons, we added the statement, "based on Ide et al.[25] and Reemtsma[31]" in Line 120.

 

Reviewer's comment:

Lines 131 : what were the R packages used ?

 

Authors' comment:

In accordance with the comment, we added "The package 'vegan' was used to conduct PerMANOVA" in Lines 138–139.

 

Reviewer's comment:

Line 183 : « DOM molecules in throughfall and stemflow… »

 

Authors' comment:

In accordance with the comment, we changed "rainwater, throughfall water, and stemflow" to "throughfall and stemflow" (Line 193). Because of this change, we also changed "rainwater, throughfall" in the previous manuscript Line 179 to "rainfall, throughfall" (Lines 190).

 

Reviewer's comment:

Lines 185-193 : what does this mean in terms of implication for water quality and the conservation role of forests/plantations of Japanese cypress ? Since the DOC flux and the number of m/z are higher in TF than RF, what can you infer, using literature, about the fate of the increased inputs of lipids, proteins (N input) and lignins/tannins from TF to forest soils ?

 

Authors' comment:

Based on the comment, we added the description that proteins in throughfall would be readily utilized by microorganisms in the forest floor because of their labile properties, which in turn can stimulate the microbial activities (Lines 204–208), as described earlier. This might enhance mineralization processes, such as nitrification and denitrification, which influence water quality. We also added the description that the large number of lignin-like molecules common to throughfall samples would be retained in forest soils because of their refractory properties and contribute to the molecular diversity in soil water (Lines 208–210). We used literature, Qualls and Haines (1992), Ide et al. (2017), and Wu et al. (2018).

 

Reviewer’s comment:

Line 193 : « dissolves and leaches plant-derived molecular species ».

 

Authors’ comment:

In accordance with the comment, we changed "absorbs" to "dissolves and leaches" in Line 204.

 

Cited literature

Ide, J.; Ohashi, M.; Takahashi, K.; Sugiyama, Y.; Piirainen, S.; Kortelainen, P.; Fujitake, N.; Yamase, K.; Ohte, N.; Moritani, M.; Hara, M.; Finér, L. Spatial variations in the molecular diversity of dissolved organic matter in water moving through a boreal forest in eastern Finland. Sci. Rep. 2017, 7, 42102, doi:10.1038/srep42102.

Qualls, R. G.; Haines, B. L.; Swank, W. T. Fluxes of Dissolved Organic Nutrients and Humic Substances in a Deciduous Forest. Ecology 1991, 72, 254, doi:10.2307/1938919.

Qualls, R. G.; Haines, B. L. Biodegradability of Dissolved Organic Matter in Forest Throughfall, Soil Solution, and Stream Water. Soil Sci. Soc. Am. J. 1992, 56, 578–586, doi:10.2136/sssaj1992.03615995005600020038x.

Reemtsma, T. Determination of molecular formulas of natural organic matter molecules by (ultra-) high-resolution mass spectrometry. J. Chromatogr. A 2009, 1216, 3687–3701, doi:10.1016/j.chroma.2009.02.033

Stubbins, A.; Silva, L. M.; Dittmar, T.; Van Stan, J. T. Molecular and Optical Properties of Tree-Derived Dissolved Organic Matter in Throughfall and Stemflow from Live Oaks and Eastern Red Cedar. Front. Earth Sci. 2017, 5, 1–13, doi:10.3389/feart.2017.00022.

Wu, X.; Wu, L.; Liu, Y.; Zhang, P.; Li, Q.; Zhou, J.; Hess, N. J.; Hazen, T. C.; Yang, W.; Chakraborty, R. Microbial Interactions With Dissolved Organic Matter Drive Carbon Dynamics and Community Succession. Front. Microbiol. 2018, 9, 1–12, doi:10.3389/fmicb.2018.01234.


Reviewer 2 Report

Dear Autors, 

The article is very interesting and informative. I think it should be published in Water because it brings a new look to the trriughfall research.


The results are well presented.

Figures are legible and self-explanatory.


There is a lack of discussion on the results and conclusions presented even in a few sentences.

It would be interesting to discuss with chemical data.

Work really has the potential and I encourage you to finish the manuscript and and I will read it again with curiosity


best regards

Author Response

We greatly appreciate the reviewer's positive comments and suggestions, which have been helpful for our revision.

 

Reviewer's comment:

Dear Autors,

The article is very interesting and informative. I think it should be published in Water because it brings a new look to the trriughfall research.

The results are well presented.

Figures are legible and self-explanatory.

There is a lack of discussion on the results and conclusions presented even in a few sentences.

It would be interesting to discuss with chemical data.

Work really has the potential and I encourage you to finish the manuscript and I will read it again with curiosity

best regards

 

Authors' comment:

Based on the comment, we discussed the data from the biogeochemical viewpoint. Specifically, we added the sentences, "Proteins are relatively labile and biodegradable compounds[36]. Given that the DOC flux and the number of proteins were much higher in throughfall than in rainfall, the spatially homogenized quality of throughfall water supports the indication of Qualls and Haines[10] that tree leaves leach readily mineralisable DOM to the rainwater, which in turn can stimulate microbial activities in the forest floor. In contrast, the large number of lignins common to throughfall samples might be retained in forest soils due to their refractory properties and thereby contribute to the molecular diversity of DOM in soil water[26]" (Lines 204–210).

We also added the description that the spatially homogenized quality of throughfall water is partly attributable to throughfall samples that we collected within a plot of the same tree species, while citing the result of the other study (Lines 211–216). Additionally, we added the description about the possibility that molecular species and their numbers of DOM in throughfall vary depending on rainfall amounts and seasons (Lines 217–226).

Based on the comment, in the end of the Discussion section, we added the summary of this study and described that further studies are needed to generalize the new biogeochemical process that we presented (Lines 227–230).

 

Cited literature

Qualls, R. G.; Haines, B. L. Biodegradability of Dissolved Organic Matter in Forest Throughfall, Soil Solution, and Stream Water. Soil Sci. Soc. Am. J. 1992, 56, 578–586, doi:10.2136/sssaj1992.03615995005600020038x.


Reviewer 3 Report

The paper entitled »The high contribution of the coniferous canopy to the molecular diversity of dissolved organic matter in rainfall« deals with DOM in rainfall and throughfall and with observed differences. The authors used a new approach of the evaluation of DOM with a Fourier transform ion cyclotron resonance mass spectrometry.

As my field of work is measurement and evaluation of rainfall interception (rainfall, throughfall and stemflow) and not its composition, I have evaluated the paper from this point of view. Therefore, I haven’t given any comments on the used method or chemical analysis.  

 

Title

The title is a bit misleading. You have only samples from the coniferous tree species, therefore the statement of “high contribution” /in comparison of what/ is not very clear. In addition, this is (according to the introduction) nothing new. Maybe you should point out that you have used a new method for evaluation of DOM in rainfall and in throughfall …

 

Introduction

Introduction gives a good description of the background. However, I would suggest to include description of rainfall interception process (what is throughfall) and interaction of rainfall with vegetation.

 

Materials and methods

Are samples from only one rainfall event enough? There was not much water collected during that event. Can amount of rainfall or any other rainfall event properties (e.g. intensity, wind characteristics, air temperature) influence results of the chemical analysis? Please specify.

Please add a figure with location of the study plots at the watershed.

 

Results

L133: The average values are probably calculated according to the five collectors? Please specify.

Figure 1: The three graphs can be positioned all in one line, using smaller font.

 

Discussion

The first paragraph of the discussion is a great start, however, this discussion is too short and doesn’t use or compare all of the results you got with the analysis. Please add some additional comparison of your results with other studies or try to explain some of your results.

You state that rainwater becomes spatially homogenous after passing the trees. Is this because you had samples from the same tree species? What would happen if there would be different trees at your study plot? How does this affect the DOM of throughfall? Please add a discussion on this.

 

Conclusions

Conclusions are missing. The last paragraph of the Discussion may be used here.

Author Response

We greatly appreciate the reviewer's critical comments and suggestions, which have been helpful for us to provide clear and concise revisions. Detailed responses are provided below.

 

Reviewer's comment:

Title

The title is a bit misleading. You have only samples from the coniferous tree species, therefore the statement of “high contribution” /in comparison of what/ is not very clear. In addition, this is (according to the introduction) nothing new. Maybe you should point out that you have used a new method for evaluation of DOM in rainfall and in throughfall ...


Authors’ comment:

Based on the comment, we deleted “high” in the title. The "molecular diversity" indicates the usage of a new method because existing methods are unable to detect hundreds or thousands of DOM molecular species in rainfall and throughfall. Therefore, we didn't add the expression about FT-ICR MS in the title.

 

Reviewer's comment:

Introduction

Introduction gives a good description of the background. However, I would suggest to include description of rainfall interception process (what is throughfall) and interaction of rainfall with vegetation.

 

Authors' comment:

In accordance with the comment, we added the description about rainfall interception process and throughfall and then started the description about the interaction between rainfall and tree canopies (Lines 51–54).

 

Reviewer's comment:

Materials and methods

Are samples from only one rainfall event enough? There was not much water collected during that event. Can amount of rainfall or any other rainfall event properties (e.g. intensity, wind characteristics, air temperature) influence results of the chemical analysis? Please specify.

 

Authors' comment:

We don’t think that samples from one rainfall event are enough. Based on the comment, we added the description that rainfall amounts and ambient temperature affect molecular species and their numbers of DOM in throughfall in the Discussion section (Lines 217–226). Additionally, we added the sentences, "This study presented the new biogeochemical process that the tree canopy can add a diverse array of DOM molecules to rainwater in a Japanese cypress plantation, based on the data obtained during a rain event. To generalize this, further studies are needed on inter-event or seasonal variations in DOM molecular species leached from the tree canopy" in Lines 227–230.

 

Reviewer's comment:

Please add a figure with location of the study plots at the watershed.

 

Authors' comment:

In accordance with the comment, we added a figure showing the location of study plots at the watershed in the supplement material.

 

Reviewer's comment:

Results

L133: The average values are probably calculated according to the five collectors? Please specify.

 

Authors' comment:

In accordance with comment, we added "among five sample replicates" in Line 141. Because of this addition, we added "among the replicates" in Line 143. We also changed "sample replicates (n = 5)" to "the replicates" in Line 145.

 

Reviewer's comment:

Figure 1: The three graphs can be positioned all in one line, using smaller font.

 

Authors' comment:

In accordance with the comment, we rearranged the three graphs in one line.

 

 

Reviewer's comment:

Discussion

The first paragraph of the discussion is a great start, however, this discussion is too short and doesn’t use or compare all of the results you got with the analysis. Please add some additional comparison of your results with other studies or try to explain some of your results.

 

Authors' comment:

In accordance with the comment, we compared our results with those of Stubbins et al. (2017) in the Discussion section (Lines 211–216). Few studies have detected DOM molecules in throughfall using FT-ICR MS, but Stubbins et al. (2017) have done it. We also discussed about the spatially homogenized quality of throughfall water from the biogeochemical viewpoint (Lines 204–210).

 

Reviewer's comment:

You state that rainwater becomes spatially homogenous after passing the trees. Is this because you had samples from the same tree species? What would happen if there would be different trees at your study plot? How does this affect the DOM of throughfall? Please add a discussion on this.

 

Authors' comment:

Based on the comment, we added the sentence, "The spatially homogenized quality of throughfall water is partly attributable to the fact that throughfall samples were collected within a plot of the same tree species" in Lines 211–212. We also added the possibility that molecular species of DOM in throughfall vary depending on tree species, while citing the result of Stubbins et al. (2017) showing that molecular species of throughfall DOM were explicitly separated between oak (Quercus virginiana Mill.) and cedar (Juniperus virginiana L.) stands in Lines 212–216.

 

Reviewer's comment:

Conclusions

Conclusions are missing. The last paragraph of the Discussion may be used here.

 

Authors' comment:

Based on the comment, we added the sentences, "This study presented the new biogeochemical process that the tree canopy can add a diverse array of DOM molecules to rainwater in a Japanese cypress plantation, based on the data obtained during a rain event. To generalize this, further studies are needed on inter-event or seasonal variations in DOM molecular species leached from the tree canopy" in the end of the Discussion section as a summary of this study (Lines 227–230).

 

Cited literature

Qualls, R. G.; Haines, B. L. Biodegradability of Dissolved Organic Matter in Forest Throughfall, Soil Solution, and Stream Water. Soil Sci. Soc. Am. J. 1992, 56, 578–586, doi:10.2136/sssaj1992.03615995005600020038x.

Stubbins, A.; Silva, L. M.; Dittmar, T.; Van Stan, J. T. Molecular and Optical Properties of Tree-Derived Dissolved Organic Matter in Throughfall and Stemflow from Live Oaks and Eastern Red Cedar. Front. Earth Sci. 2017, 5, 1–13, doi:10.3389/feart.2017.00022.

 

Reviewer 4 Report

The manuscript contains interesting data of Japanese cypress canopy influence on molecular diversity of dissolved organic matter in rainwater.  The methodology used, Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) is developed relatively recently and allows  to detect different types of molecules in DOM based on the cyclotron frequency of charged ions in a magnetic field. Until now, it has mostly been used to provide mass spectrum of DOM in river and marine water samples. Therefore, this application on open rainfall and tree canopy troughfall has novelty value.

The paper is relatively well written and easy to follow. I have only some few remarks to be clarified. The two compartments of which the molecular diversity is determined are named ‘rainfall’ and ‘throughfall’. I would prefer adding the word ‘open’  in connection with the rainfall to avoid misunderstandings: “rainfall in the open” or “open rainfall”. I would also prefer to have the explanations of the molecular classes in the figure captions 1 and 2, instead of referring to material and methods

Author Response

We greatly appreciate the reviewer's positive comments and suggestions, which have been helpful for our revision.

 

Reviewer's comment:

The manuscript contains interesting data of Japanese cypress canopy influence on molecular diversity of dissolved organic matter in rainwater. The methodology used, Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) is developed relatively recently and allows to detect different types of molecules in DOM based on the cyclotron frequency of charged ions in a magnetic field. Until now, it has mostly been used to provide mass spectrum of DOM in river and marine water samples. Therefore, this application on open rainfall and tree canopy troughfall has novelty value.

The paper is relatively well written and easy to follow. I have only some few remarks to be clarified. The two compartments of which the molecular diversity is determined are named ‘rainfall’ and ‘throughfall’. I would prefer adding the word ‘open’ in connection with the rainfall to avoid misunderstandings: “rainfall in the open” or “open rainfall”. I would also prefer to have the explanations of the molecular classes in the figure captions 1 and 2, instead of referring to material and methods

 

Authors' comment:

Based on the comment, we changed "rainfall" to "bulk deposition (rainfall)" in the Abstract section. We also changed "rainfall" to "bulk deposition (rainfall)" in the captions of Figures 2 and 3. Additionally, we changed "rainfall" to "bulk deposition" in Line 93 and added the sentence, "In this study, bulk deposition collected in the open area was referred to as rainfall" in Lines 95–96. Because of these changes, we standardized the expressions, "rainwater and throughfall water" and "rainfall and throughfall water" to "rainfall and throughfall". We also changed "throughfall water collectors" to "throughfall collectors" in Line 94.

In accordance with the comment, we added the explanation of molecular classes in the caption of Figure 2 (Lines 165–167). Because of this addition, we deleted the sentence, "See the Materials and methods section for the abbreviations of biomolecular classes" from the caption of Figure 2. We also changed "See the Materials and methods section" to "See Figure 2" in the caption of Figure 3 (Lines 180).


Round 2

Reviewer 2 Report

All comments have been made.

The entire article is clearly written


Author Response

Reviewer's comment:

All comments have been made.

The entire article is clearly written


Authors' comment:

We thank the reviewer for evaluating our manuscript.


Reviewer 3 Report

All of my comments were taken into account by the authors and were suitably considered in the manuscript. Especially the Discussion section has been significantly improved. I have only a few minor comments according to the changes they have made.

Figure S1: Why putting it in supplement? I believe it would better belong in the manuscript. However, I leave this decision to the authors.

The authors have mentioned the "problem" of only one event in the end of the discussion. Please mention this also at the beginning of the manuscript. I suggest you stress this out in section 2.2 Water sampling. 

Please cite also Figures S2 and S3 in the manuscript.



Author Response

We greatly appreciate the reviewer's positive comments and suggestions, which have been helpful for our revision.

 

Reviewer's comment:

Figure S1: Why putting it in supplement? I believe it would better belong in the manuscript. However, I leave this decision to the authors.


Authors' comment:

We would like to put Figure 1 in the supplement material, because this study was conducted at a plot scale and focused on vertical changes in DOM molecules in a forest and putting the map of the study watershed in the manuscript might confuse readers.

 

Reviewer's comment:

The authors have mentioned the "problem" of only one event in the end of the discussion. Please mention this also at the beginning of the manuscript. I suggest you stress this out in section 2.2 Water sampling.


Authors' comment:

Based on the comment, we added the statement, “though the quantity and quality of DOM can vary depending on rain event characteristics, such as rainfall amounts[31]” in Lines 101–102. We also added “just” before “one rain event” in Line 100. We cited the literature, Parker (1983).

 

Reviewer's comment:

Please cite also Figures S2 and S3 in the manuscript.


Authors' comment:

We have cited “Figures S2 and S3” in Line 116.

 

Cite literature:

Parker, G. G. Throughfall and Stemflow in the Forest Nutrient Cycle. In Advances in Ecological Research (vol. 13); Academic Press, 1983; pp. 57–133.


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