Round 1

Reviewer 1 Report (Previous Reviewer 1)

After modification, the quality of the article has been improved to some extent. I have no other comments.

Author Response

Please find attached the answer to the reviewers. 

Author Response File: Author Response.docx

Reviewer 2 Report (New Reviewer)

Review Sellan et al.

Assessment of wet inorganic nitrogen deposition in an oil palm plantation-forest matrix environment in Borneo

 

Study main aim

Authors:

To assess, for the first time, the amount of wet NH4+ and NO3- deposition near the boundary of the pristine Kabili-Sepilok Forest Reserve, Sabah, Malaysia.

To considered whether the monthly N deposition pattern correlates with agricultural and forest fires or with fertiliser volatilised from agricultural areas

Comment:

The aims and the hypotheses to be tested in the study are not clearly expressed. This can be improved.

Background

Authors:

Few measurements of N deposition exist for Malaysian Borneo. Borneo has widespread N-limited forests such as heath forests and montane forests, so an increase in N deposition could lead to biodiversity loss.

These forests are likely to undergo seasonal haze pollution from fires and N deposition due to the fertilisation of plantations.

The rate of N deposition is predicted to increase in tropical areas …

Comment:

More information of the N deposition to tropical forests is highly needed.

Scientific approach and methods

Authors:

Collection Sabah Forestry Department’s Forest Research Cen-70 tre (FRC) in Sepilok, Sabah, Malaysia

Comment:

It would have been informative with a comment on how representative this sampling site is for tropical forests in the region.

Authors:

Sampling and analysis, wet-only sampler. Sampling was carried out two times per week. over a period of 12 months from September 2016 to August 2017. Only one rain gauge collector.

Comment:

The are in many cases problems with wet-only samplers, that they are not opening in light rain. The chemistry in light rain may well be different from heavy rain events. Was this checked? Was is mostly heavy rain at this monitoring site?

The sampling time of 12 months is rather short, since wet deposition depends strongly on meteorology. Was it described if the meteorology during these 12 months was representative for longer time periods?

Using only one rain gauge also is a severe limitation.

Authors:

Results refer to wet-deposited inorganic N only

Comment:

A pity org-N was not analyzed…

Main results

Authors:

Line 184: We found no significant correlation between any N form or rainfall pH with MFC and the MLUC (Table 2; p>0.05 in all cases). Table 2. The p- values were adjusted using the Benjamini-231 Hochberg false discovery rate, and were all non-significant.

Comment:

Please show the p values in Table 2. Using p>0.05 for significance is no universal law. Using the Benjamini-Hochberg false discovery rate adjustment is to my understanding a very strict criteria, making it difficult to obtain significance.

Main conclusions

Authors:

It is likely that the total N deposition in our study site exceeds the critical load of 10-15 kg N ha-1 yr-1.

…we did not find any correlation between monthly wet inorganic N deposition or concentration in rainwater and the number of fires that winds coming to our study site intercepted

Comment:

It is surprising with the high amounts of wet deposition of inorg-N detected. As the authors recognize, dry deposition of N might add a similar size additional deposition. It is even more surprising that no correlation is found with potential fires plumes.

What about ship traffic and heavy industry emission sources in the region?

Overall comments to the manuscript

Measurements of N deposition to tropical forest land is urgently needed, so this article is important from this point of view. On the other hand, measurements extended only one year and dry deposition was not measured.

Overall, I still think that this paper is worth publishing.

Details

Line 46: N critical load of 10-20 kg N ha-1 yr-1 [9]…

Comment: There are newer sources for the CL of N: Bobbink, R., and Hettelingh, J.-P. (2011). Review and revision of empirical critical loads and dose-response rela-tionships. Proceedings of an expert workshop, Noordwijkerhout, 23-25 June 2010. Proceedings of an expert work-shop, Noordwijkerhout, 23-25 June 2010, CCE. doi:http://www.rivm.nl/bibliotheek/rapporten/680359002.pdf

The CLs for deposition of N in Europe are currently under revision: https://www.umweltbundesamt.de/publikationen/review-revision-of-empirical-critical-loads-of

Line 99: … to obtain the bulk wet deposition

Comment: Since wet-only samplers was used, this should in principle be wet deposition ?

Line 126: … becomes less dense with increasing distance from the fire itself

Comment: This is of course a simplification and depends on the meteorology and thus the air mass movements. There are examples of very long transport for fire plumes, e.g. Stohl, A., Berg, T., Burkhart, J.F., Fjæraa, A.M., Forster, C., Herber, A., Hov, Ø., Lunder, C., 2007. Arctic smoke e record high air pollution levels in the European Arctic due to agricultural fires in Eastern Europe. Atmospheric Chemistry and Physics 7, 511e534. This plume carried a lot of NH4-N, Karlsson, P.E., Martin Ferm, Hans Tømmervik, Lars R. Hole, Gunilla Pihl Karlsson, Tuija Ruoho-Airola, Wenche Aas, Sofie Hellsten, Cecilia Akselsson, Teis Nørgaard Mikkelsen, and Bengt Nihlgård. 2013. Biomass burning in eastern Europe during spring 2006 caused high deposition of ammonium in northern Fennoscandia. Environmental Pollution, 176, 71–79.

Figure 3.

Comment: Please explain the red dots.

 

 

Author Response

Please see the attachment

Author Response File: Author Response.docx

This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.

Round 1

Reviewer 1 Report

1. How do agricultural activities affect oil palm plant-Forest? It's not clear in the introduction and methodology.

2. Why only measure nitrogen components in precipitation? Does this characterize nitrogen deposition? Are there any contrast points or background values?

3. Table 1, the units are kg/ha, how are they calculated?

4. What is the relationship between forest fire, wind, and precipitation when designing the experiment?

5. In the discussion, through the comparative analysis of data, what do you want to show?

6. Many details of the article need to be proofread, such as superscript and subscript, "NH4+" should be "NH⁴⁺".

7. Author Contributions, why not write the author's name?

Reviewer 2 Report

see the attached file

Comments for author File: Comments.pdf

Reviewer 3 Report

This study documents the highest annual wet inorganic nitrogen deposition in the Malaysian forest environment. The data measured in this study contribute to the study of nitrogen cycling in the region.

 

Suggestions for Authors:

Line 91: H2SO4. Samples were then stored in a -20⁰ C refrigerator until NH4+ and NO3-; Note the upper and lower labeling of the compound.

Line 95: The inorganic nitrogen in this study only contains ammonium and nitrate. What is the concentration of nitrite?

Line 99: Please list the calculation formula separately.

Line 147: Before describing the concentration distribution of nitrogen species, please give an overview of the climatic state of the study area.

Line 284: Wet deposition flux is mainly affected by rainfall. Therefore, it is suggested that Table 3 should list the rainfall of each study site.

The literature cited in this study is too old. It is recommended to compare the research data in recent years.