The Distribution and Migration of ¹³⁷Cs in Oak (Quercus serrata) and Cedar (Cryptomeria japonica) Forest Organic Fractions

Round 1

Reviewer 1 Report

The article presented for a review entitled “The distribution and migration of ¹³⁷Cs in oak (Quercus serrata) and cedar (Cryptomeria Japonica) forest organic fractions”, deals with the role of different layers of organic horizon both deciduous oak and coniferous cedar to vertical ¹³⁷Cs distribution. The experiment was conducted via laboratory column-based method. The article discusses an important problem of recognition and evaluation of potential mobility of radioactive Cs in forest under the influence of fresh, relatively undecomposed, and partially decomposed forest litter of two species. 

In my opinion, the article should have some corrections, especially the description of experimental setup should be improved. Below some suggestion for manuscript improvement are given:

1. Methodology description, especially the part about soil sampling and… should be improved. In description sampling methods only information about depth of soil column sampling was given (0-10 cm). However, no data about soil horizons were added. The introduction section slightly  suggest that mineral soil horizons were taken (lines 91-94) but values of soil bulk density given in the table 1 are characteristic for organic horizon. Please add information about soil horizon sampled during preparation of soil column.

 

2. The amounts of a particular organic fraction given were added to the top of soil columns based on data of Sasaki (data unpublished). Did these data were obtained from Field Museum Tamakyuryo site or Fukushima Daiichi Nuclear Power Plant? (lines 173-176). Could you also explain the abbreviation of A­₀.

 

 

3. Taking into consideration that element migration in soil column experiment is only connected with water migration, information about soil moisture during experiment period should be given. There is a lack of such data. So the question arise at which level of humidity soil was incubated during experiment.
4. In Figure 1. the Authors use term Brown Forest soil, however further in the text they gave information that soil was classified according to WRB (2006) as Cambisol. In the WRB (2006) it is mentioned that Cambisol in other soil classification systems refer to Brown soils/Brown Forest soils (older US systems). However, it is not suggested term for this group of soil. Please be consistent with term and classification system through the whole text. Line 148 “….of brown forest soil” – please be consistent with WRB classification.
5. Authors used in line 63 term “…..shallow soil (0-0.05) in forests:” In soil science shallow soil are defined as soil that have less than 50 cm depth of solum. Please change the statement, for example “..in the thin top layer of soil.”
6. In my opinion, the text of the manuscript should be re-analysed in the manner of the terms used in it, mainly soil layers. In my opinion, the term soil horizon should appear in part of the text instead soil layer.

 

Editorial remarks: 

1. According to the guidelines of the journal, the abbreviation should be explained at the first moment of its appearance. This provision is to help the potential reader to fully understand the text being read. In the reviewed article, abbreviations are explained several times in the further part of the text, not at the time of their first appearance in the text. Please review the text of the manuscript and correct these shortcomings. This applies in particular to the abstract paragraph (e.g. lines 19-20 “..L- and F organic fractions…”; line  27 “… the F-layer….”). Other example: FM abbreviation appears first in Figure 1 – lines 104-107, but its explanation is given in line 121. Please change this according to journal guidelines.
2. Line 114 lack of coma “…. oak site respectively”, it should be “…. oak site, respectively”
3. Lines 119-120 lack of coma “….28±7.1 cm respectively”, it should be “…. ….28±7.1 cm, respectively.”
4. Figure 3a. on the scheme of column experimental setup organic layer studied in this research were denoted as Ol and Of. According to Guidelines for Soil Description 4^th edition such suffixes do not exist in WRB 2006 for O and H horizon. Additionally, change the term Brown forest soil for Cambisol to be consistent with selected soil classification system.
5. Table 3, mass depth appears as a soil physicochemical properties. In soil science such a term does not functioning. This is a function of soil bulk density.
6. According to guidelines for authors manuscript should have fallowing sections: Introduction, Materials and Methods, Results, Discussion and Conclusions. Please follow the journal guidelines or discuss the matter with the Editor.

Comments for author File: Comments.pdf

Author Response

Reviewer #1

1. Methodology description, especially the part about soil sampling and... should be improved. In description sampling methods only information about depth of soil column sampling was given (0-10 cm). However, no data about soil horizons were added. The introduction section slightly suggest that mineral soil horizons were taken (lines 91-94) but values of soil bulk density given in the table 1 are characteristic for organic horizon. Please add information about soil horizon sampled during preparation of soil column

Response:

Thank you for the important point suggested. The manuscript has been modified per the suggestions giving for improvement of the manuscript and clarity of readers.

 

2. The amounts of a particular organic fraction given were added to the top of soil columns based on data of Sasaki (data unpublished). Did these data were obtained from Field Museum Tamakyuryo site or Fukushima Daiichi Nuclear Power Plant? (lines 173-176). Could you also explain the abbreviation of Ao.

Response:

Thank you for the observation. The data were obtained from Osawa, Nihonmatsu City, Fukushima Prefecture. Also Ao is the O- Horizon, which is the organic horizon of the soil. The manuscript has been modified per the suggestion for improvement and clarity.

 

3. Taking into consideration that element migration in soil column experiment is only connected with water migration, information about soil moisture during experiment period should be given. There is a lack of such data. So the question arise at which level of humidity soil was incubated during experiment.

Response:

Thank you for the observation pointed out. The manuscript has been modified per the suggestion to provide further information for clarity and improvement of the manuscript.

 

4. In Figure 1. the Authors use term Brown Forest soil, however further in the text they gave information that soil was classified according to WRB (2006) as Cambisol. In the WRB (2006) it is mentioned that Cambisol in other soil classification systems refer to Brown soils/Brown Forest soils (older US systems). However, it is not suggested term for this group of soil. Please be consistent with term and classification system through the whole text. Line 148 ..of brown forest soil" — please be consistent with WRB classification.

Response:

Thank you for the suggestion. The manuscript has been modified per the suggestion.

 

5. Authors used in line 63 term ".....shallow soil (0-0.05) in forests:" In soil science shallow soil are defined as soil that have less than 50 cm depth of solum. Please change the statement, for example "..in the thin top layer of soil."

Response:

Thank you for the suggestion. The manuscript has been modified per the suggestion.

 

6. In my opinion, the text of the manuscript should be re-analysed in the manner of the terms used in it, mainly soil layers. In my opinion, the term soil horizon should appear in part of the text instead soil layer

Response:

Thank you for the suggestion. They have been considered and the manuscript modified accordingly.

 

 

Editorial remarks:

1. According to the guidelines of the journal, the abbreviation should be explained at the first moment of its appearance. This provision is to help the potential reader to fully understand the text being read. In the reviewed article, abbreviations are explained several times in the further part of the text, not at the time of their first appearance in the text.

Please review the text of the manuscript and correct these shortcomings. This applies in particular to the abstract paragraph (e.g. lines 19-20 "..L- and F organic fractions.

line 27 the F-layer...."). Other example: FM abbreviation appears first in Figure 1 — lines 104-107, but its explanation is given in line 121. Please change this according to journal guidelines.

Response:

Thank you for the shortcomings pointed out. They are acknowledged and the manuscript has been modified accordingly.

 

2. Line 114 lack of coma oak site respectively", it should be oak site, respectively"

Response:

Thank you for the shortcomings pointed out. They are acknowledged and the manuscript has been modified accordingly

3. Lines 119-120 lack of coma "...28±7.1 cm respectively", it should be 28±7.1 cm, respectively."

Response:

Thank you for the suggestion pointed out. They are acknowledged and the manuscript has been modified accordingly

 

4. Figure 3a. on the scheme of column experimental setup organic layer studied in this research were denoted as 01 and Of. According to Guidelines for Soil Description 4th edition such suffixes do not exist in WRB 2006 for O and H horizon. Additionally, change the term Brown forest soil for Cambisol to be consistent with selected soil classification system.

Response:

Thank you for the suggestion pointed out. They are acknowledged and the manuscript has been modified accordingly

 

5. Table 3, mass depth appears as a soil physicochemical properties. In soil science such a term does not functioning. This is a function of soil bulk density.

Response:

Thank you for the suggestion. We would be glad if the statement would be made clear for understanding and modification of the manuscript for improvement.

 

6. According to guidelines for authors manuscript should have fallowing sections: Introduction, Materials and Methods, Results, Discussion and Conclusions. Please follow the journal guidelines or discuss the matter with the Editor.

Response:

Thank you for the suggestion pointed out. We followed the guidelines for authors according to the journal guidelines. According to the guidelines, the Discussion section, “…may be combined with Results”

 

We would like to extend our sincere gratitude to you for your suggestions and comments to better our manuscript

Reviewer 2 Report

The migration of radionuclides in forest ecosystems is an important problem of radioecology. In this research, an original approach is applied to the experimental study of the migration of radiocesium. The research was done at a high scientific level and can be published in the Forests journal

Please check the captions for Figure 2

The behavior of radionuclides in forest ecosystems became the focus of attention after the Chernobyl accident. It turned out that forest ecosystems are practically not subject to self-purification, and the inventory of technogenic radionuclides in them, in particular, 137Cs, decreases mainly due to physical decay. This is of great practical importance, in particular for residents of the territories of Russia, Ukraine and Belarus living in contaminated areas, whose diet traditionally includes mushrooms and berries.

The second surge of interest in the problem occurred after the Fukushima accident, then there were many publications devoted to the forests of Japan and comparing the consequences of the two largest radiation accidents. The authors of the reviewed manuscript also made significant contributions to these studies.

But despite the abundance of publications, our understanding of processes in forest ecosystems is still insufficient. We do not fully understand how the redistribution of radionuclides between ecosystem components occurs and what factors are decisive. It turned out that radionuclides entering with litter often migrate in the soil layer faster than those that entered with atmospheric fallouts. The manuscript under review is devoted to the study of the role of organic matter in the migration of radionuclides.

The original approach used by the authors is of interest. Most researchers analyze the distribution of radionuclides in the soil layer and try to build a mathematical model that describes the observed distribution. The authors of this work took a different path - they conducted a long-time laboratory experiment using forest litter (fresh and partially decomposed) and uncontaminated soil samples. Thus, the experiment made it possible to separate from the total mass a part of the factors influencing the migration of radionuclides in the forest ecosystem.

Measurement of radioactivity was carried out in accordance with relevant approaches, using modern equipment, software and appropriate standard reference materials.

Experiments have shown differences in cesium migration for deciduous and coniferous forests, consisting of the two most important for the region  tree species - oak (Quercus serrata) and cedar (Cryptomeria Japonica). The authors also determined a number of numerical parameters characterizing the vertical distribution of cesium-137 in soil columns.

As a suggestion, the authors would like to add some refences describing the experimental method with a soil column, if any. The question also arises of how the results of such laboratory experiments can be further applied to the real conditions of forest ecosystems where soil fauna, fungi, etc. can play a significant role in migration. Perhaps this should be discussed in more detail.

Author Response

Reviewer #2

As a suggestion, the authors would like to add some references describing the experimental method with a soil column, if any. The question also arises of how the results of such laboratory experiments can be further applied to the real conditions of forest ecosystems where soil fauna, fungi, etc. can play a significant role in migration. Perhaps this should be discussed in more detail.

Response:

Thank you for the suggestions pointed out. They are well noted and the manuscript is modified accordingly for improvement and clarity for readers. In regards to the application in real conditions, we stated in Line 165-167, the sampling was done to mimic real condition and natural prediction of ¹³⁷Cs distribution. In addition, consistency of this study to field studies are may indicate success of the methodology to real conditions. Nonetheless, we have considered the feasibility of the laboratory experiment to real conditions for accuracy

 

Reviewer 3 Report

Minor English edits

Line 56. What about tree turnover resulting in root upheaval?

Methods

Explicitly state the soil used was the Cambisol

Soil moisture was maintained. What measures were made to prevent the litter drying out (dry litter does not decay)?

Figure 2 are oak, cedar labels correct?

Table 2 Not clear at what stage these measurements were made; C, N and Cs contents at the start or end of the incubation? Was change in these properties measured over the study period? Also need information about how much the leaf litter decomposed. The initial inputs are clearly stated. How much of each litter type was recoverable at the end of the experiment? 

The soil depth distribution appears to have been modeled. Was this validated using the soil depth data? Why was a model used when measured data  was available?

Were soil biota present in the soil columns? Both macro and micro soil organisms have been shown to transfer organic matter along with organically bound contaminants.

Line 277 do you mean "most"

Line 290 Make clear which study (Koarashi and Atarashi-Andoh)

Line 365 Capitalise the first word

 

Author Response

Reviewer #3

Line 56. What about tree turnover resulting in root upheaval?

Response:

We agree that turnover due to root upheaval is one important feature that are considered to affect ¹³⁷Cs availability in soil. We mentioned forest litter and organic horizons as some of the major factors considered in ¹³⁷Cs availability as those are the main focus of this study.

 

Methods

Explicitly state the soil used was the Cambisol

Response:

Thank you very much for the suggestion. The corresponding sections have revised accordingly.

 

Figure 2 are oak, cedar labels correct?

Response:

Rightly said, these are oak and cedar labels with the respective L-fractions of easily recognizable originally shaped organic components made up of periodically falling raw litter and F fraction composed of an early fermented and fragmented litter component in which the original shapes of the litter were not easily identified

 

Table 2 Not clear at what stage these measurements were made; C, N and Cs contents at the start or end of the incubation? Was change in these properties measured over the study period? Also need information about how much the leaf litter decomposed. The initial inputs are clearly stated. How much of each litter type was recoverable at the end of the experiment?

Response:

Thank you for the important observations pointed out. C, N and Cs contents were all measured at the after the incubation. Therefore, the properties were not measured over the study as the incubation was once for the 5-month period. It is agreed that such data is relevant. However, that data as requested was not measured and will be considered in future studies for clarity and deeper understanding of the forest litter layer fractions to Cs distribution and migration in forest soils.

 

 

The soil depth distribution appears to have been modeled. Was this validated using the soil depth data? Why was a model used when measured data was available?

Response:

The measured data is not a good indicator to determinate the strength of penetration and hence migration of ¹³⁷Cs. Using the exponential function, the determined relaxation depth values gives a proper estimation of the distribution, penetration strength and migration of ¹³⁷Cs

 

 

Were soil biota present in the soil columns? Both macro and micro soil organisms have been shown to transfer organic matter along with organically bound contaminants.

Response:

Thank you for this important point. Such macro organisms were absent and unnoticeable. Even though microorganisms such as bacteria and fungi, this study did not consider such factor as a main objective of this study. Nonetheless, it will be considered for future research study.

 

Line 277 do you mean "most"

Response:

The suggestion pointed out was not noticed in Line 277. However, the manuscript has been modified for clarity.

 

Line 290 Make clear which study (Koarashi and Atarashi-Andoh)

Response:

Thank you for the suggestion. However, we seem not to understand fully the suggestion giving. With the respect the reference to Line 290, the exponential function was referenced (Becks, 1966)

 

 

Line 365 Capitalise the first word

Response:

Thank you for the suggestion. However, we could not find the suggestion pointed out for correction. Nonetheless all capitalizations have made where necessary.

 

We would like to extend our sincere gratitude to you for your suggestions and comments to better our manuscript.