Activity of 137Cs and 40K Isotopes in Pine (Pinus sylvestris L.) and Birch (Betula pendula Roth) Stands of Different Ages in a Selected Area of Eastern Poland
Round 1
Reviewer 1 Report
The investigation seems to be carried out normally, and I imagine the work using 36 trees must be tough.
After such tough work, it is quite unfortunate that in the present manuscript, the aim, hypotheses, and design of the study do not fit together (actually, the aim of the study is not clearly described). I really think it is impossible to evaluate the effects of both soil K-40 content and the tree age on the tree Cs-137 contamination in this investigation.
If you wanted to test your hypothesis “(ii) the activity of the 40K isotope in the soil influences the activity of 137Cs in wood and forest litter (line 85)”, you should have chosen some stands with same age and different soil K content. Consequently, I cannot agree with your conclusion saying that “The results of our research confirmed the literature data on the antagonistic behavior of 137Cs and 40K isotopes (line 297)”. You should notice that the value of TF Cs-137 in 80-years-old forest can be greatly distorted by the direct fallout, and that TF Cs-137 in 30- and 50-years-old forest (Fig. 4A) is not inversely correlated with soil K-40 content (Fig. 2C).
Reading the manuscript, it seems that the unique feature of this study is providing the data of 80-years-old pine and birch trees. I recommend focusing on this point, and simply discuss how birch wood is useful in assessing Cs-137 contamination in the environment over time.
In this process, the questions such as; Is the bark in the year 1945-1962 still remained as the bark in the 80-years-old trees? Is birch tree a “accurate” tool to assess environmental contamination considering that they do not show the contamination due to Chernobyl accident ? , should be addressed. Additionally, you might suggest whether the influence of soil K-40 content on the TF Cs-137 is big or not with referring some other publications. Especially, you should keep in mind that soil K-40 content (Bq/kg) can not necessarily correlate with plant available soluble K content (mg/kg), which significantly affect plant Cs+ uptake.
When you revise the manuscript, you need to check carefully all the figures and tables for defects and mistakes (including statistics).
Author Response
To Reviewer 1:
We are very grateful for your valuable comments regarding our manuscript ID: forests-1335422. In the revised version, we took into account the comments of both Reviewers. You will find our responds to your suggestions below. We will be grateful for further comments that will improve the quality of our work.
Best regards,
Elżbieta Królak
The aim, hypotheses, and design of the study do not fit together (actually, the aim of the study is not clearly described). ….it is impossible to evaluate the effects of both soil K-40 content and the tree age on the tree Cs-137 contamination in this investigation.
Following your suggestion, the passage (ii) “the activity of the 40K isotope in the soil influences the activity of 137Cs in wood and forest litter” has been removed from the hypotheses, and the hypothesis: “(iii) the activity of 137Cs in stands in different age groups enables the assessment of radioactive contamination of the studied area in the past” has been introduced.
As a consequence, Fig. 4, illustrating the relationship between the activity of 137Cs and 40K in the analyzed ecosystem, has been removed from the manuscript. The sentence: "The results of our research confirmed the literature data on the antagonistic behavior of 137Cs and 40K isotopes" has also been deleted.
Additionally, you might suggest whether the influence of soil K-40 content on the TF Cs-137 is big or not with referring some other publications.
It has been completed, as you suggested. The relevant literature data (6th paragraph in Discussion) has also been provided.
I recommend focusing on this point, and simply discuss how birch wood is useful in assessing Cs-137 contamination in the environment over time.
The information has been added to the discussion of the results (second last paragraph in the Discussion).
Additionally, as suggested by Reviewer 2, we supplemented the Materials and Methods with the information concerning the number of trees belonging to each species (6 individual trees of each species and age group).
The conclusions has been corrected so that they correspond to the hypotheses.
Reviewer 2 Report
The manuscript presents highlights on current radioecological conditions in the Poland forest ecosystem. One of the main findings of the work shows significantly greater radioactive contamination of the environment in eastern Poland after the nuclear tests rather than the Chernobyl NPP accident. The manuscript is well-written and fits the Scope of Forests journal. It can be published after the correction of several remarks and giving the proper information on sample sizes.
Line 72 – 109 -> please, consider 109
Lines 96-97 – this part is important. The sample size is totally unclear. You mention 36 trees in total, but how many trees belong to each species? How many trees were in each age group? A table must be added here, clearly specifying sample sizes for each species and each age group.
Line 130 and further ‒ “Bq/Mg” – what do you mean? Milligram? Megagram? Please explain. Mg is written as mg, not Mg.
Lines 188-189, 214-215 – It is incorrect to say that “presence of potassium influences activity” or “activity influences content”. Сausal relationship is broken here.
Author Response
To Reviewer 2:
We are very grateful for your valuable comments regarding our manuscript ID: forests-1335422. In the revised version, we took into account the comments of both Reviewers. You will find our responds to your suggestions below.
Best regards,
Elżbieta Królak
Line 72 – 109 -> please, consider 109 - corrected
Lines 96-97 – this part is important. The sample size is totally unclear. You mention 36 trees in total, but how many trees belong to each species? How many trees were in each age group? A table must be added here, clearly specifying sample sizes for each species and each age group.
We supplemented the Materials and Methods with the information concerning the number of trees belonging to each species (6 individual trees of each species and age group).
Line 130 and further ‒ “Bq/Mg” – what do you mean? Milligram? Megagram? Please explain. Mg is written as mg, not Mg.
It has been explained in the Materials and Methods in the fourth paragraph: in fresh weight of 1 Mg (tons) of wood.
Lines 188-189, 214-215 – It is incorrect to say that “presence of potassium influences activity” or “activity influences content”. Сausal relationship is broken here.
Lines 188-189 – following the suggestion of both Reviewers, this passage has been removed
Lines 214-215 – deleted from the manuscript
Round 2
Reviewer 1 Report
The revised manuscript looks largely improved in terms of logical flow.
I wonder why you do not carry out statistical analysis in some of the figure. You need to carefully check all the data presenting in the paper.
Author Response
Dear Reviewer,
We are very grateful for your comments on statistical calculations regarding our manuscript ID: forests-1335422.
In the caption for Figure 1, we have included information about the letter markings in this figure; the designations refer to the case of the simultaneous dependence: age x stand type (see Table 1). They complement the data contained in Table 1. In Figure 1 B, we added the missing letter “b” at the age of 50.
We hope that the above supplement meets your expectations. Thank you very much for your insightful and constructive review of our manuscript.
Best regards,
Elżbieta Królak
Reviewer 2 Report
Thank you, I am satisfied with the changes made.
Author Response
Dear Reviewer,
We are very grateful for accepting the revised version of our manuscript ID: forests-1335422 and for all your constructive comments.
Best regards,
Elżbieta Królak
