The Impact of Air Pollution on the Growth of Scots Pine Stands in Poland on the Basis of Dendrochronological Analyses†
Round 1
Reviewer 1 Report
This ms is complete in the classic sense of academic journal articles: an extensive Introduction of rationale for the study, complete Methods, lots of Results, reasonable Discussion and Conclusions, and 70 References listed. The data set is extensive. Here are comments and suggestions for consideration in revision:
Page 1: Correspondence is repeated twice.
Figures in general: Maybe it’s just my age and weakening eyesight, but I found most of the text of the figures to be too small on printed pages to read comfortably. Perhaps my reading the paper on screen would allow zooming in on the figures.
Page 5, upper: “The lowest level of precipitation was observed between the mid-1980s and Mid-1990s (Figure 2).” I don’t see this statement illustrated at all in Figure 2, nor in any other figure for that matter. Is this a typo?
Figure 3 (the first one, on page 5): The red and blue temperature lines are really 1 deg C apart from one another? Not that I don’t trust it, but those lines appear to overlap each other nearly entirely. This might be a case of compression of the y-axis, which ranges up to 50 deg C even though the data lines max out at 20 deg C. I’d cut the y-axis range off at 20 deg C and truly demonstrate a difference in temperature between the red and blue lines.
Page 5, bottom: “fresh mixed coniferous forest”? I’m not familiar with this usage of fresh.
Page 6, upper: Residual chronologies were analyzed? In dendro, residual means something very specific, usually requiring an explanation for why residual versus standard chronologies.
Page 6, middle: the mean value was used to characterize the chronologies? The overall means of dendrochronologies analyzed in this way should all be 1.0, therefore not really a useful characterization across chronologies.
Page 7, top: There’s a second Figure 3? Obviously a case of misnumbering, which must be corrected. Additionally, I’m not even sure if this figure was referred to in the text. Either way, the expression immensely serious air pollution caught my eye. That’s just not a common way of describing air pollution.
Figure 4: I would have started the x-axis labels at a more round number, like 1910. Or maybe even 1900 and used less labels and a bigger font. Plus, tree-ring chronologies are simply easier to interpret when they come with a 1.0 reference line overlain on them. I see (but only barely) the light gray gridlines, but a solid black 1.0 reference line would be helpful.
Figure 5: Two lines per plot? Is the green line the same in all cases? From P8? No explanation is given in the caption. No y-axis scales? No axis titles? “Start of fertilizer plant” is not the title of the x-axis. And, no P7 plot?
Figure 6: Caption says these are distributions, but they seem to be time series plots, plotted as if they were distributions. No P8 data? I’d guess the %trees values for P8 are mostly 0, which would reinforce the point here, but I’m not sure what plotting a bunch of 0s would do. The scales for the brown bars at the bottom should be better associated with their actual bars.
Figure 7: Again, the scales for the brown bars at the bottom should be better associated with their actual bars.
Author Response
Please see the attachment.
Author Response File: 
Author Response.docx
Reviewer 2 Report
General comments
The manuscript “The Impact of air pollution on the growth of Scots Pine stands in Poland on the basis of dendrochronological analysis” evaluates the degradation of pine stands located in the proximity of a fertilizers factory in southern Poland due to heavy and prolonged environmental contamination with pollutants as well as the recovering trend in trees radial growth following the strong reduction in emissions of nitrogen compounds.
The paper is well structured and clearly written, the applied methodology is scientifically sound and the results of the dendrochronological analysis are finely exposed and discussed in the context of the pollution records history of the site. Some of the described ecological changes in ecosystem properties related to the Scots pine stands degradation, are not evidenced by data or supporting literature. In my view, this is currently the major shortcoming of the paper, which should be addressed to eliminate the purely qualitative and speculative nature of the discussion section related to the ecological dynamics triggered by heavy pollution.
Specific comments
Figure 1. Replace "Change of ekosystem" with "Ecosystem change"
L148: please provide an explanation in the text of the terms "dry and fresh coniferous forests" or provide an alternative classification .
Since both forests are reported to grow in the same area on "sandy soils..suffering from periodical water deficits", that denotes dry conditions, it is particularly unclear what the Authors mean with the term "fresh". Moreover in L 227-228 it is stated that "all the stands under study represented a fresh mixed coniferous forest habitat.." that conflicts with L148.
L 166-167: "the concentration of pollutants reached 1000-1200 kg ha-1 a-1". How were these concentration values assessed? Were atmospheric N depositions monitored? Do these values refer to the pollutants accumulation measured in the top soil?
Figure 2. What do the blue areas on the map of Poland represent? Please explain.
L184-185. "The lowest level of precipitation was observed between the mid 180s and mid 1990's (Fig2)". This is not shown in fig.2, but actually neither in fig.3, which shows the mean climatology for the period 1951-1990 and 1991-2015.
L273 "..DendroClim2002 software [60]". The correct reference is [61]
L305 " In plot 4, the reduction could still be observed in the sampling year". Unclear or possibly incomplete sentence, please rephrase.
L307-308. Caption of Figure 5 provides limited and incomplete information and it should be therefore extended. What is the difference between the blue and the red arrows? what do the green vertical bars indicate? Add a legend in the graph or explain in the caption what do the brown and green lines stand for in the plots.
Figure 9. Distances from the pollution source (0.2, 1.4, 5 km) should be moved to the positions in the figure as currently they are clumped together.
L369-370 change into "..in particular by increasing the difference between maximum and minimum air temperature,"
L370-371 changes in air humidity in which direction? (higher/lower levels). You probably mean "Decrease in mean air moisture levels" here.
Is there an evidence of the actual direction of these changes in the studied forests? Sparse forest cover areas following trees die-back could potentially feature lower water demand from the tree canopy cover resulting in a larger available water amount for the remaining standing trees.
L383-384 Is there any evidence (supporting data or publication) of the reported “changes to soil fauna and microbes and of the microbial activity”?
L386 Was the “deterioration of tree growth conditions” limited to Pinus sylvestris or did it affec also other tree species? Or all of them? Please add this detail in the text.
L 411 Figure 11 – caption. In did not find Table S.2, which is supposed to contain the correlation coefficients, in the Supplementary Material!
Figure 11. The color codes in the legend include only the correlations with winter temperature and not with summer precipitation.
Interestingly the correlation coefficient between TRW and mean air temperature of winter months decreases over time in the reference plot, while that with summer precipitation increases, witnessing the ongoing climate change with milder winters and drier summers. This result can be underlined in the results and discussion section, in the context of the actual and projected effect of climatic changes on tree productivity in particular relation to drought periods.
Supplementary Material – Table S1
Pine share – not clear what this variable is (Canopy cover area (%)?)
Forest Habitat Type – Unclear classification, polish characters.
Type of soil – (Typical/Brown) rusty soil. Please specify the used soil classification system and preferably provide the equivalent soil type according to an international (WRB, US Soil Taxonomy) soil classification scheme.
Author Response
Dear Reviewer,
Thank you very much for your review, for your time devoted to reading our work, and for your effort in reviewing our manuscript. Thank you for your very valuable and useful comments and suggestions. Thank you also for appreciating our research. Your comments allowed us to significantly improve the manuscript. We tried, as technically possible, to take into account all your comments. Please find attached the revised manuscript “The Impact of Air Pollution on the Growth of Scots Pine Stands in Poland based on Dendrochronological Analyses” by Longina Chojnacka-Ożga & Wojciech Ożga. The manuscript has been revised according to the useful comments and suggestions of the reviewers, as detailed in the itemized responses below.
General comments
The manuscript “The Impact of air pollution on the growth of Scots Pine stands in Poland on the basis of dendrochronological analysis” evaluates the degradation of pine stands located in the proximity of a fertilizers factory in southern Poland due to heavy and prolonged environmental contamination with pollutants as well as the recovering trend in trees radial growth following the strong reduction in emissions of nitrogen compounds.
The paper is well structured and clearly written, the applied methodology is scientifically sound and the results of the dendrochronological analysis are finely exposed and discussed in the context of the pollution records history of the site. Some of the described ecological changes in ecosystem properties related to the Scots pine stands degradation, are not evidenced by data or supporting literature. In my view, this is currently the major shortcoming of the paper, which should be addressed to eliminate the purely qualitative and speculative nature of the discussion section related to the ecological dynamics triggered by heavy pollution.
Thank you very much for your valuable general comments. We agree with the Reviewer that some of the changes in the ecological properties of ecosystems described in the Discussion, related to the degradation of pine stands, are not evidenced by data or supporting literature. The environmental impact of emissions from the nitrogen fertiliser factory in Pulawy is described in many publications (unfortunately in Polish), these we referred to in the Introduction and Study area. However, as the Reviewer aptly pointed out, the lack of such a description in the discussion and the lack of reference to literature may raise concerns purely (speculative nature). Hence, we agree with a comment/suggestion of the Reviewer that the reference to literature should be included with each information provided in the discussion and the concept we developed (Figure 11). We have included references in the revised version of the article and we hope that now our description will not be speculative.
We apologize for all errors/displacements/ inaccurate checking in the Figures. We also sincerely apologize for errors in the numbering and reference to the figures. We have made a mistake in the numbering from Figure 4, thus, the numbering of all figures has changed. We changed few figures and added the explanation. We hope that our Figures are now easier to understand for the reader.
A detailed list of responses to your comments is provided below (in red)
Specific comments
Figure 1. Replace "Change of ecosystem" with "Ecosystem change" –
Done. Thank you very much to the reviewer for this comment, we apologize for this error.
L148: please provide an explanation in the text of the terms "dry and fresh coniferous forests" or provide an alternative classification .
Since both forests are reported to grow in the same area on "sandy soils..suffering from periodical water deficits", that denotes dry conditions, it is particularly unclear what the Authors mean with the term "fresh". Moreover in L 227-228 it is stated that "all the stands under study represented a fresh mixed coniferous forest habitat.." that conflicts with L148.
Thank you very much for your valuable comment. Sentences have been corrected. Currently, it is:
The industrial plant was built on the western edge of a large forest complex, in an area covered by oligotrophic habitats types, dominated by Scots pine, formed on sandy soils low in nutrients and suffering from periodical acute water deficits.
The description of the area around the plant was made based on literature, perhaps a bit uncritically. Thank you and we apologize for our mistake.
L 166-167: "the concentration of pollutants reached 1000-1200 kg ha-1 a-1". How were these concentration values assessed? Were atmospheric N depositions monitored? Do these values refer to the pollutants accumulation measured in the top soil?
The data provided in the manuscript in these lines concern the deposition of pollutants in the first years of operation of the factory in places of the highest concentration. The data was made available by Zakłady Azotowe Puławy and is also quoted in the literature. The sentence has been supplemented with data sources.
In the early years of the plant’s operation, the deposition of pollutants reached 1000–1200 kg ha-1 a-1 (42, 46, 48, 51).
We apologize for using the word concentration incorrectly instead of deposition. Thank you very much for your valuable comment.
Additionally, we would like to inform you about the scale of pollution in the first decade of the plant's operation.
In the first years of operation of the plant, the forests around the plant were filled with an aerosol of ammonium nitrate (fog made of ammonium nitrate). Within a few years, a zone of biological death was established here. Such a high nitrogen deposition was reflected, for example, in the accumulation of nitrogen in the needles. In the 1970s, the total nitrogen content in pine needles reached 30/40 mg / g, mineral nitrogen, mainly N-Nh4 3-5 mg / g. The pine needles were up to 20 cm long!
Figure 2. What do the blue areas on the map of Poland represent? Please explain.
Thank you very much for your valuable comment, the lack of an explanation of the signatures made the map unreadable. The caption for the figure has been supplemented. We also added literature describing changes in the forests around other plants.
L184-185. "The lowest level of precipitation was observed between the mid 180s and mid 1990's (Fig2)". This is not shown in fig.2, but actually neither in fig.3, which shows the mean climatology for the period 1951-1990 and 1991-2015.
We thank the reviewer to notice this rough error. We apologize for this error. This has been corrected.
L273 "..DendroClim2002 software [60]".
The correct reference is [61] – done
L305 " In plot 4, the reduction could still be observed in the sampling year". Unclear or possibly incomplete sentence, please rephrase.
The sentence has been corrected, we hope it is now clearer. In plot 4, the reduction in growth began in 1968 and was still visible in 2015.
L307-308. Caption of Figure 5 provides limited and incomplete information and it should be therefore extended. What is the difference between the blue and the red arrows? what do the green vertical bars indicate? Add a legend in the graph or explain in the caption what do the brown and green lines stand for in the plots.
Thank you very much for your next valuable comment. Currently, it is Figure 6. We have added the following explanation. We hope that our Figure is now easier to understand for the reader.
Explanation of markings: Brown lines - pine chronologies on research plots, green line pine growth on the reference plot. Red horizontal arrows indicate the period of word reduction on surfaces located in the zone up to 3 km from the factory, blue arrows indicate the period of reduction of rings on surfaces located further from the factory. Vertical green lines indicate which the period to be taken into account when calculating the rate of growth reduction, following the Schweingruber method [59], e.g. diagram P1 - the reduction period lasts from 1967 to 1995 (28 years), hence the preceding period 1938-1966 was used for the calculation of the reduction rate. See explanation in the text, methods section.
Figure 9. Distances from the pollution source (0.2, 1.4, 5 km) should be moved to the positions in the figure as currently they are clumped together.
Thank you very much for your next valuable comment. We apologize for errors/displacements in this Figure (currently it is Figure 10). We made it in a vector form, where, unfortunately, sometimes the text is distorted. We apologize for our defects and inaccurate checking of the Figure. In the revised version this Figure is corrected.
L369-370 change into "..in particular by increasing the difference between maximum and minimum air temperature,"
Thank you very much for your help in reformulating our sentences.
L370-371 changes in air humidity in which direction? (higher/lower levels). You probably mean "Decrease in mean air moisture levels" here.
Is there an evidence of the actual direction of these changes in the studied forests? Sparse forest cover areas following trees die-back could potentially feature lower water demand from the tree canopy cover resulting in a larger available water amount for the remaining standing trees.
We agree with the Reviewer that such changes may take place. However, as we wrote further, the situation in Puławy was a bit different. According to earlier studies, the thinning of the crown resulted in more sunlight penetrating to the bottom of the forest which combined with a transitory increase in soil fertility enabled profuse development of the undergrowth, particularly that of birch and oak, as well as of bushes. Those plants benefited from the increased supply of nitrogen, which while being toxic to the pine tree, was necessary for their good growth. The makeup of the undergrowth started to shift towards species characteristic of forest clearing habitats, most of them thriving on nitrogen-rich soils. The profuse development of the undergrowth contributed to the increase in water demand and, as result, it contributed to both a fast depletion of nutrients and an increased water deficit. We added additional literature to our description
L383-384 Is there any evidence (supporting data or publication) of the reported “changes to soil fauna and microbes and of the microbial activity”?
Yes, we added additional literature to our description.
L386 Was the “deterioration of tree growth conditions” limited to Pinus sylvestris or did it affec also other tree species? Or all of them? Please add this detail in the text.
We added information.
Interestingly, unlike the Scots pine, the emission from the nitrogen fertiliser factory in Puławy had a beneficial effect on oak and larches trees growing in the experimental Forest Range Ruda in Puławy (ca 3 km from factory), [66]. In the case of larch, an increase in the width of the annual rings was observed during the first decades of exposure to pollution, while oak increased its growth throughout the pollution period. According to Karolewski et al. [66], it is related both to the lower sensitivity of these trees to pollution than Scots pine, as well as to the fertilizing effect of nitrogen compounds.
L 411 Figure 11 – caption. I did not find Table S.2, which is supposed to contain the correlation coefficients, in the Supplementary Material! –
Sorry, we corrected caption and we added Figure S.2 instead Table S2 in Supplementary Material.
Figure 11. The color codes in the legend include only the correlations with winter temperature and not with summer precipitation.
Interestingly the correlation coefficient between TRW and mean air temperature of winter months decreases over time in the reference plot, while that with summer precipitation increases, witnessing the ongoing climate change with milder winters and drier summers. This result can be underlined in the results and discussion section, in the context of the actual and projected effect of climatic changes on tree productivity in particular relation to drought periods.
Supplementary Material – Table S1
Pine share – not clear what this variable is (Canopy cover area (%)?) – we corrected it
Forest Habitat Type – Unclear classification, polish characters- we corrected it
Type of soil – (Typical/Brown) rusty soil. Please specify the used soil classification system and preferably provide the equivalent soil type according to an international (WRB, US Soil Taxonomy) soil classification scheme - corrected
Thank you once again for your comments and we hope that the revised version will be approved by you.
Best regards,
Authors
