Imbalanced phosphorus and nitrogen deposition in China's forests

Du, Enzai; de Vries, Wim; Han, Wenxuan; Liu, Xuejun; Yan, Zhengbing; Jiang, Yuan

doi:https://doi.org/10.5194/acp-16-8571-2016

Articles | Volume 16, issue 13

https://doi.org/10.5194/acp-16-8571-2016

© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.

https://doi.org/10.5194/acp-16-8571-2016

© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.

Articles | Volume 16, issue 13

Research article

|

14 Jul 2016

Research article |

| 14 Jul 2016

Imbalanced phosphorus and nitrogen deposition in China's forests

Enzai Du, Wim de Vries, Wenxuan Han, Xuejun Liu, Zhengbing Yan, and Yuan Jiang

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Final revised paper (published on 14 Jul 2016)
Supplement to the final revised paper
Preprint (discussion started on 16 Feb 2016)
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Interactive discussion

Status: closed

AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment

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RC1: 'Review', Anonymous Referee #1, 22 Mar 2016
- AC1: 'Reply to interactive comment on “Imbalanced phosphorus and nitrogen deposition in China’s forests” by Anonymous Referee #1', E.Z. Du, 23 Apr 2016
RC2: 'important analysis- but more analysis needed.', Anonymous Referee #2, 24 Mar 2016
- AC2: 'Reply to interactive comment on “Imbalanced phosphorus and nitrogen deposition in China’s forests” by Anonymous Referee #2', E.Z. Du, 23 Apr 2016

Peer-review completion

AR: Author's response | RR: Referee report | ED: Editor decision

AR by Enzai Du on behalf of the Authors (30 Apr 2016) Author's response Manuscript

ED: Referee Nomination & Report Request started (11 May 2016) by Frank Dentener

RR by Anonymous Referee #1 (24 May 2016)

Suggestions for revision or reasons for rejection

This is still a potentially publishable manuscript, however there are a few edits that need to be made.

I would like to heavily encourage the authors to submit a revised manuscript with all the changes highlighted and indicate in the response to reviewers exactly the text changed. Because this was not done, I had to reread the entire manuscript, and thus, perhaps I have found elements that were in the first version, but would have missed if the authors has highlighted their changes more effectively.

The question of what kind of deposition the authors are looking at is better explained in the methods section: I see there the highlighted changes. However, I am still not sure that these aren’t the soluble N and P, instead of total deposition. Because of the methods shown, and the uncertainty about what exactly this deposition is, I would like to encourage the authors to be more clear that they are using wet deposition in both the abstract, introduction and conclusions.

In the response to the reviewers, the authors indicate that they are very interested in ecological impacts in managed forests, which is really interesting and important and should be added to the introduction, and more so to the results and conclusions. If they are interested in ecological impacts, aren’t they more interested in N:P ratios in the deposition? Following the ideas of Brahney et al., 2016, shouldn’t they look at how N:P ratios in vegetation relate to the deposition ? The P deposition is much more effective (14x), because less P is required. How does that change the conclusions of this study?

“Based on measurements of P content in various fuels and estimates of the P partitioning during combustion processes, a recent assessment indicates that anthropogenic sources, such as combustion-related emissions, can contribute to over 50% of the global atmospheric P and make a substantial contribution to global P deposition (Wang et al., 2015).” This is not correct. They get this large number by ignoring size differentiation between their model (<20um) and locally produced primary biogenic aerosols, and assuming that deposition in forests generated by locally produced biogenic aerosols (in Tipping et al., 2013) comes from combustion instead. Using different assumptions, Brahney et al., 2015 shows that one can match the Tipping et al., 2013 data, as well as other data constraining the size of the combustion sources (as done in Mahowald et al., 2008, but not done in Wang et al., 2015). Please rewrite to “Based on assumptions of the P partitioning during combustion processes and local deposition, a recent assessment hypothesizes that anthropogenic sources, such as combustion-related emissions, can contribute to over 50% of the global atmospheric P budget (Wang et al., 2015), although this result is very sensitive to assumptions about size distribution (Brahney et al., 2016).”

“Anthropogenic sources have been traditionally thought to make only a small contribution to P deposition (Okin et al., 2004; Mahowald et al., 2008). In contrast, our results emphasize that anthropogenic sources near large cities can have significant impacts on the spatial patterns of regional P deposition. The urban hotpot of P deposition might be derived from intensive combustion-related emissions near urban areas (Wang et al., 2015) and a short-distance transfer of P-containing aerosols from P-rich farmland soils (Anderson et al., 2006).” Again, as in the first version, the Mahowald et al., 2008 study also has hotspots close to cities, so this it is not correct that you need huge P sources from combustion to get this result. Also, you get maximum values close to the arid regions. Please be more clear on this. I would suggest something like: “Anthropogenic sources have been traditionally thought to make only a small contribution to P deposition (Okin et al., 2004; Mahowald et al., 2008), and yet can still result in local hotspots of deposition (e.g. Mahowald et la., 2008: Wang et al., 2015) along with P from arid regions, which is consistent with our study. The urban hotpot of P deposition might be derived from intensive combustion-related emissions near urban areas (Wang et al., 2015) and a short-distance transfer of P-containing aerosols from P-rich farmland soils (Anderson et al., 2006).”

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RR by Anonymous Referee #2 (10 Jun 2016)

ED: Reconsider after minor revisions (Editor review) (10 Jun 2016) by Frank Dentener

AR by Enzai Du on behalf of the Authors (15 Jun 2016) Author's response Manuscript

ED: Reconsider after minor revisions (Editor review) (24 Jun 2016) by Frank Dentener

AR by Enzai Du on behalf of the Authors (28 Jun 2016) Author's response Manuscript

ED: Publish as is (28 Jun 2016) by Frank Dentener

AR by Enzai Du on behalf of the Authors (28 Jun 2016)

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Short summary

Accelerated N emissions in China may lead to an imbalance of atmospheric nutrient inputs in various ecosystems. Our assessment of P and N deposition in China's forests showed relatively high rates of P deposition, but they were accompanied by even much higher N deposition, resulting in high N : P deposition ratios. P and N deposition both showed a power-law increase with closer distance to the nearest large cities. Our results suggest an anthropogenic imbalance of regional N and P cycling.