Pollution-Induced Changes in the Composition of Atmospheric Deposition and Soil Waters in Coniferous Forests at the Northern Tree Line

Round 1

Reviewer 1 Report

Dear Authors

  Your manuscript: "Pollution-induced changes in the composition of atmospheric deposition and soil waters in coniferous forests at the northern tree line" presents an interesting theme and similar articles have already been published. Regarding its manuscript, the writing needs a thorough review, mainly referring to concordance and structure. Improve the description of the experimental design and explain the unbalanced sampling process. It would be interesting for you to comment further on this condition and its implications for the results. It is noticed that some conclusions are not properly referred to the initial objectives of the work. Here are some suggestions for your analysis:

     1) Lines 62 to 64: further detail the objectives: General and specific or, if you prefer, cite the goals.

     2) Lines 68: “6 permanent monitoring sites”. Further detail the choice and availability of these sites. Statistically, this number is sufficient. Explore this condition further.

      3) Figure 1: Improve image visualization. Use letters in the figure (a,b) and explain them in the title of the figure.

     4) Lines 185 to 192: “to 0.87 mg/l (R2 = 0.37) in spruce forests, from 0.87 to 0.62 mg/l (R2 = 0.29) in pine forests”. Please comment on the low value obtained for R². In general, your coefficient of determination. Another aspect concerns the verification of data normality which is not properly explained.

    5) In the tables, use bold to highlight the most significant values. It helps in reading the discussions.

    6) In the discussions, it would be interesting to cite the results obtained by other authors to assist in the analyzes presented. This feature is little explored in your article.

    7) Are the increases in pollutant indices related to the increase in smelting activities? It would be interesting to present the evolution of production versus the increase in indices.

       8) As it is a phenomenon with strong spatial dependence, this aspect should be better explored in the results, better contextualizing the greater concentration of indices with the proximity of the foundries. My suggestion would be to incorporate, not necessarily in this manuscript but in a future study, the variographic analysis.

       9) The Mann-Whitney test is cited but its results are not properly explored. For future studies, I recommend as an alternative to Statistica, I present the Real Statistics application, the interesting plug-in for Excel (https://www.real-statistics.com/).

     I conclude my analysis by congratulating them for the work performed and for the presented version of the manuscript.

Respectfully,

Comments for author File: Comments.pdf

Author Response

Reply to the reviewer

of the article Vyacheslav Ershov, Tatyana Sukhareva, Ludmila Isaeva, Ekaterina Ivanova and Gennady Urbnavichus Pollution-induced changes in the composition of atmospheric deposition and soil waters in coniferous forests at the northern tree line

Dear Reviewer.

Thank you for your feedback, constructive criticism and questions that have improved our article and to which we answer.

1. Lines 62 to 64: further detail the objectives: General and specific or, if you prefer, cite the goals.

In accordance with the recommendation, the purpose of the study was supplemented.

2. Lines 68: “6 permanent monitoring sites”. Further detail the choice and availability of these sites. Statistically, this number is sufficient. Explore this condition further.

The objects of this study were atmospheric fallout and soil water in dwarf shrub-green moss spruce forests and lichen-shrub pine forests. Field studies were carried out on 6 permanent monitoring sites (PMS) of the Institute of Industrial Ecology Problems of the North at the KSC RAS in Murmansk region, Russia (Figure 1). PMS were established in typical forest ecosystems of the region in automorphic landscape positions. PMS are within transport accessibility for regular surveys. Text was corrected.

3. Figure 1: Improve image visualization. Use letters in the figure (a,b) and explain them in the title of the figure.

The drawing has been corrected as recommended

4. Lines 185 to 192: “to 0.87 mg/l (R2 = 0.37) in spruce forests, from 0.87 to 0.62 mg/l (R2 = 0.29) in pine forests”. Please comment on the low value obtained for R². In general, your coefficient of determination. Another aspect concerns the verification of data normality which is not properly explained.

The coefficient of determination (0.29) is low due to the high variability of long-term data on the composition of snow water. In this case, we tried to show not only patterns, but also trends in sulfate concentrations. Our data were not tested for a normal distribution due to high variability, since normality would be low. Thank you for your comment, which we will try to take into account in future work.

5. In the tables, use bold to highlight the most significant values. It helps in reading the discussions.

All tables present mean concentrations with standard error. The calculation of the reliability of differences (p) was carried out for under-crown and inter-crown spaces and stages of digression. Significant differences were reflected in the text and were not inserted into the table due to the large amount of data. Therefore, it is extremely difficult to highlight individual values in bold.

6. In the discussions, it would be interesting to cite the results obtained by other authors to assist in the analyzes presented. This feature is little explored in your article.

Thanks for the comments, changes have been made to the text

7. Are the increases in pollutant indices related to the increase in smelting activities? It would be interesting to present the evolution of production versus the increase in indices.

Yes, that would be really interesting. But unfortunately, we do not have this information, so we cannot make a comparison.

8. As it is a phenomenon with strong spatial dependence, this aspect should be better explored in the results, better contextualizing the greater concentration of indices with the proximity of the foundries. My suggestion would be to incorporate, not necessarily in this manuscript but in a future study, the variographic analysis.

Thank you for your valuable advice and we will try to take it into account in further research.

9. The Mann-Whitney test is cited but its results are not properly explored. For future studies, I recommend as an alternative to Statistica, I present the Real Statistics application, the interesting plug-in for Excel (https://www.real-statistics.com/).

The study of the Man Whitney test was carried out fully. But due to the huge amount of data obtained, it is not advisable to include them in the article. Many thanks for the recommendation on the statistical processing of data, which we will try to include in future studies.

Once again, we thank you for your comments, remarks and recommendations, which allowed us to improve our article.

Reviewer 2 Report

This study examines the dynamics of the composition of atmospheric precipitation and soil water in coniferous forests (dwarf shrub-green moss spruce and lichen-shrub pine) under the influence of atmospheric emissions from the Severonickel Copper-Nickel Smelter in Russia’s Murmansk region. The results showed that the concentrations of main pollutants (sulfates and heavy metals) in atmospheric fallout and soil water are higher than in the background areas significantly. On the basis of collecting historical precipitation data for 10 years, the selection of sampling points, sampling methods and statistical analysis are basically reasonable, but the analysis of results needs to be further refined to provide the basis for assumptions, guesses, and relevant literature supporting the interpretation of possible causes. The following issues also need to be explained and improved.

1.       Line 184-185 in page 6, …Between the crowns in defoliating forests, a decrease in sulfate concentrations was observed, from 0.1 to 0.87 mg/l (R2 = 0.37),… Is there any mistake in the expression, expressing the opposite meaning?

2.       Line 207-208 in page 7, ….Elevated concentrations of elements under the crowns indicate leaching of element compounds from plant tissues. Whether the elements (Ca、Mg、Ni、C、Cu、SO42-) under the crown comes from fallen leaves or plant tissues. It is impossible to draw such a conclusion from the current data, and there is no literature to support such conjectures and assumptions.

3.       Line 238-240 in page 8, ….This pattern is explained by a lower content of organic acids due to poor forest stand condition and a significant increase in sulfate concentrations when exposed to industrial air pollution. There should be criteria for the quality of forest stand conditions. Please improve how to explain the poor forest stand conditions and the basis.

4.       Line 252-254 in page 8,……the deposition of C a significant decrease compared to the background area, which is due to crown defoliation. The background areas is defoliating forests (Figure 1), also falling leaves, How can we know that C of defoliating forests and pollution-induced sparse forests is lower than that of background area?

5.       Line 268-270 in page 8,……Elevated concentrations of element compounds in the rainfall under the crowns of spruce forests are associated with a larger surface area and more pronounced barrier functions of spruce tree crowns. There should be literature to support this conjecture.

6.       Line 306-308 in page 10,…….In pine forests, on the contrary, acidity is higher under tree crowns, which is explained by a large amount of atmospheric precipitation, especially stem water, leaching the soil under pine crowns. This explanation is far fetched.

7.       Line 340-345 in page 13,…Under conditions of industrial air pollution, this can be explained by an increase in the supply of acid-forming substances from the atmosphere, especially under the crowns, and a disruption in the functioning of the phytocenosis. In defoliating spruce forests, the ANC index in the soil water from all soil horizons between the crowns is significantly higher than under the crowns, which may be due to the intense flow of acid-forming substances with precipitation under spruce crowns. Why is it that the function of plant community is disrupted under the tree crown? How to understand the intense flow of acid-forming substances with precipitation under spruce crowns? There should be literature to support this conjecture.

8.       Line 361, in page 14, ……This may be due to an increase in the concentration of bases associated with the composition of parent rocks. Line 373, in page 14, ……which is explained by parent rocks rich in bases. These two sentences refer to the parent rock, please quote the background data of the sample point and the literature about the parent rock.

9.       In Figure 2, among many heavy metal pollution elements, why only the change trend of Ni is studied? Is there any particularity? Suggest adding other elements or explaining the uniqueness of Ni.

10.   The whole experimental design is not innovative.

11.   There are too many conclusions, and 5 points are listed. It is suggested to combine similar conclusions, which need further refining.

Author Response

Reply to the reviewer

of the article Vyacheslav Ershov, Tatyana Sukhareva, Ludmila Isaeva, Ekaterina Ivanova and Gennady Urbnavichus. Pollution-induced changes in the composition of atmospheric deposition and soil waters in coniferous forests at the northern tree line

Dear Reviewer.

Thank you for your feedback, constructive criticism and questions that have improved our article and to which we answer.

1. Line 184-185 in page 6, Between the crowns in defoliating forests, a decrease in sulfate concentrations was observed, from 0.1 to 0.87 mg/l (R2 = 0.37) Is there any mistake in the expression, expressing the opposite meaning?

Yes, there is an error. Must be: «Between the crowns in defoliating forests, a decrease in sulfate concentrations was observed, from 1.1 to 0.87 mg/l (R2 = 0.37)». Corrected in text

2. Line 207-208 in page 7, Elevated concentrations of elements under the crowns indicate leaching of element compounds from plant tissues. Whether the elements (Ca, Mg, Ni, C, Cu, SO₄^2-) under the crown comes from fallen leaves or plant tissues. It is impossible to draw such a conclusion from the current data, and there is no literature to support such conjectures and assumptions.

Numerous studies have shown that the concentrations of elements in atmospheric fallout under the crowns of woody plants are higher than in the spaces between the crowns and in open areas. This is explained by flushing and leaching of elements from the crowns of woody plants. Corrected and added links to the text.

3. Line 238-240 in page 8, This pattern is explained by a lower content of organic acids due to poor forest stand condition and a significant increase in sulfate concentrations when exposed to industrial air pollution. There should be criteria for the quality of forest stand conditions. Please improve how to explain the poor forest stand conditions and the basis.

The text has been amended and clarified, which was implied by the poor state of the stand

4. Line 252-254 in page 8 the deposition of C a significant decrease compared to the background area, which is due to crown defoliation. The background areas is defoliating forests (Figure 1), also falling leaves, How can we know that C of defoliating forests and pollution-induced sparse forests is lower than that of background area?

Defoliating forests is a term denoting the stage of technogenic digression, was introduced by Lukina N.V. and Nikonov V.V., based on the analysis of the state of forest stands and the features of biogeochemical cycles of elements. The decrease in carbon in rainwater in forest stands at the stages of defoliating forests and pollution-induced sparse forests compared to the background area is shown in Table 2 and is explained by the deterioration of the crowns of woody plants.

5. Line 268-270 in page 8, Elevated concentrations of element compounds in the rainfall under the crowns of spruce forests are associated with a larger surface area and more pronounced barrier functions of spruce tree crowns. There should be literature to support this conjecture.

References to literary sources are added to the text.

6. Line 306-308 in page 10, In pine forests, on the contrary, acidity is higher under tree crowns, which is explained by a large amount of atmospheric precipitation, especially stem water, leaching the soil under pine crowns. This explanation is farfetched.

Thank you very much for the note. The correction has been made to the text.

7. Line 340-345 in page 13, Under conditions of industrial air pollution, this can be explained by an increase in the supply of acid-forming substances from the atmosphere, especially under the crowns, and a disruption in the functioning of the phytocenosis. In defoliating spruce forests, the ANC index in the soil water from all soil horizons between the crowns is significantly higher than under the crowns, which may be due to the intense flow of acid-forming substances with precipitation under spruce crowns. Why is it that the function of plant community is disrupted under the tree crown? How to understand the intense flow of acid-forming substances with precipitation under spruce crowns? There should be literature to support this conjecture.

At the stage of defoliating forests and pollution-induced sparse forests, an increase in sulfate concentrations in comparison with the background in atmospheric precipitation and soil waters was revealed, which is shown in Tables 2 and 3. Coniferous trees act as an absorbent for pollutants. Therefore, when passing through the tree canopy, precipitation is enriched with pollutants, which significantly affects the chemical composition of soil water. Links to research data are given above line 310

8. Line 361, in page 14, This may be due to an increase in the concentration of bases associated with the composition of parent rocks. Line 373, in page 14, ……which is explained by parent rocks rich in bases. These two sentences refer to the parent rock, please quote the background data of the sample point and the literature about the parent rock.

Corrected and added links to the text.

9. In Figure 2, among many heavy metal pollution elements, why only the change trend of Ni is studied? Is there any particularity? Suggest adding other elements or explaining the uniqueness of Ni.

Figure 2 shows exactly the concentration of Ni, because for this element the most pronounced trends were revealed. The concentrations of other pollutants showed significant variability and did not show pronounced trends.

10. The whole experimental design is not innovative.

Such long-term studies of the composition of atmospheric precipitation and soil water in the northern taiga forests at the intra- and inter-biogeocenotic level are unique.

11. There are too many conclusions, and 5 points are listed. It is suggested to combine similar conclusions, which need further refining.

Corrected in text

Once again, we thank you for your comments, remarks and recommendations, which allowed us to improve our article.

Round 2

Reviewer 1 Report

Dear Authors

  The second version of your article: "Pollution-induced changes in the composition of atmospheric deposition and soil waters in coniferous forests at the northern tree line" presented interesting improvements that make the experiment easier to understand.

     Thank you for sending the cover letter with the answers to my questions.

     Congratulations on the work done.

Respectfully,

Author Response

Dear reviewer. We thank you for your valuable comments and advice, which helped us improve our article.
Sincerely, the team of authors

Reviewer 2 Report

Among the 11 questions raised last time, the fourth and seventh questions need to be improved again.

4. Line 252-254 in page 8,……the deposition of C a significant decrease compared to the background area, which is due to crown defoliation. The background areas is defoliating forests (Figure 1), also falling leaves, How can we know that C of defoliating forests and pollution-induced sparse forests is lower than that of background area?

7. Line 340-345 in page 13,…Under conditions of industrial air pollution, this can be explained by an increase in the supply of acid-forming substances from the atmosphere, especially under the crowns, and a disruption in the functioning of the phytocenosis. In defoliating spruce forests, the ANC index in the soil water from all soil horizons between the crowns is significantly higher than under the crowns, which may be due to the intense flow of acid-forming substances with precipitation under spruce crowns. Why is it that the function of plant community is disrupted under the tree crown? How to understand the intense flow of acid-forming substances with precipitation under spruce crowns? There should be literature to support this conjecture.

Author Response

Reply to the reviewer

of the article Vyacheslav Ershov, Tatyana Sukhareva, Ludmila Isaeva*, Ekaterina Ivanova and Gennadii Urbanavichus. Pollution-induced changes in the composition of atmospheric deposition and soil waters in coniferous forests at the northern tree line

Dear Reviewer.

Thank you for your feedback, constructive criticism and questions that have improved our article and to which we answer.

4. Line 252-254 in page 8 the deposition of C a significant decrease compared to the background area, which is due to crown defoliation. The background areas is defoliating forests (Figure 1), also falling leaves, How can we know that C of defoliating forests and pollution-induced sparse forests is lower than that of background area?

We conducted research in the background area (Fig. 1 - e), as well as in conditions of aerotechnogenic pollution: at the stage of defoliating forests (Fig. 1 - c and d) and at the stage of pollution-induced sparse forests (Fig. 1 - a and b).

Fallouts, as well as carbon concentrations in rain in defoliating forests and pollution-induced sparse forests, are significantly lower compared to the background area, with the exception of defoliating pine forests, here the differences are not significant (p > 0.05). Similar results were obtained in earlier studies, where it was found that in pollution-induced sparse forests, the concentration of carbon in atmospheric fallout was lower compared to the background values, which is associated with a sharp decrease in the mass of needles and a significant influx of sulfates, nitrates and chlorides with emissions from the copper-nickel smelter [Lukina, N.V.; Nikonov, V.V. Biogeochemical cycles in the forests of the North under aerotechnogenic pollution, Part. 1, Apatity, Russia, 1996, 216 p., P 115-121.]. The text was corrected (lines 269 – 277).

7. Line 340-345 in page 13, Under conditions of industrial air pollution, this can be explained by an increase in the supply of acid-forming substances from the atmosphere, especially under the crowns, and a disruption in the functioning of the phytocenosis. In defoliating spruce forests, the ANC index in the soil water from all soil horizons between the crowns is significantly higher than under the crowns, which may be due to the intense flow of acid-forming substances with precipitation under spruce crowns. Why is it that the function of plant community is disrupted under the tree crown? How to understand the intense flow of acid-forming substances with precipitation under spruce crowns? There should be literature to support this conjecture.

The function of the plant community under the crowns is disturbed due to the transformation of descending atmospheric technogenic flows. The acidity and composition of atmospheric precipitation in this case is controlled by two additional factors - the level of atmospheric pollution and the degree of damage to the tree canopy. The acidity of atmospheric precipitation sharply increases, and the concentrations of sulfates, nickel and copper in their composition increase significantly. An increase in the concentrations of basic cations is observed due to their leaching from the crown as a result of the action of acid precipitation. Under the conditions of aerotechnogenic pollution, due to the presence of the tree canopy, the lower layers of vegetation, the soils of tree parcels, and the trees themselves are exposed to a more powerful technogenic impact than the vegetation and soils of intercrown parcels.    Nikonov, V.V.; Lukina, N.V.; Bezel' V.S. et al. Scattered elements in boreal forests, Izd-vo: Nauka Moscow, Russia, 2004, 616 p., P. 73-74. The text was corrected (lines 382 – 387).

Once again, we thank you for your comments, remarks and recommendations, which allowed us to improve our article.