Fine Root Biomass Mediates Soil Fauna Community in Response to Nitrogen Addition in Poplar Plantations (Populus deltoids) on the East Coast of China
Round 1
Reviewer 1 Report
Dear authors,
I think you provide a fine work which can bring significant improvement to the knowledge of the soil faunal community. My only concern is that you do not state in any way in the manuscript how you identified the animal specimens and how you define the named groups. The proceedings doing this task have to be urgendly stated because there is no way to judge the correctness of you results and conclusions without them. Further did you store the identified animals in a scientific collection as voucher material? If done so, please name the place and collection, if not state the proceeding for the animal material after the end of the study. If the named tasks are done I will be pleased to see the final version of the publication.
Comments for author File: 
Comments.pdf
Author Response
Response to Reviewer 1 Comments
General comments: I think you provide a fine work which can bring significant improvement to the knowledge of the soil faunal community. My only concern is that you do not state in any way in the manuscript how you identified the animal specimens and how you define the named groups. The proceedings doing this task have to be urgendly stated because there is no way to judge the correctness of you results and conclusions without them. Further did you store the identified animals in a scientific collection as voucher material? If done so, please name the place and collection, if not state the proceeding for the animal material after the end of the study. If the named tasks are done I will be pleased to see the final version of the publication.
Response : The groups of the fauna in the same order were identified according to Yin [1, 2]. Detailed description could be found in Lines 169-170 and 177-178 on Page 4. In addition, soil fauna were stored in the glass bottles filled with ethanol (75 %) in our lab.
Point 1: add page break
Response 1: Done as suggested.
Point 2: It would be very interesting for you to read and to cite Raub et al. Basic and Applied Ecology (2014). "No Bottom-Up effect of food addition on predators in a tropical forest." in the respect of effects of changes in the soil faunal community by adding ressources (as food). Raub et al. could also show an increase of the decomposer soil fauna by aading N-rich food sources.
Response 2: We read and cite this paper in Lines 58-59, Page 2:
“In addition, Raub, et al. [3]confirmed the positive effect of N-rich food resource on the abundance of soil fauna. ”
Point 3: Elevated intraguild predation could also be a factor masking effects on the total soil fauna!
Response 3: Good suggestion. We have added “elevated intraguild predation” in Line 66, Page 2 as one of the factors leading to non-significant N addition effect on soil fauna.
Point 4: Do not forget fungi!
Response 4: Done as suggested.
Point 5: See again Raub et al. 2014
Response 5: We read and cite this paper.
Point 6: ...of the whole soil fauna...
Response 6: Done as suggested.
Point 7: Please give a Köppen climate classification. See https://en.wikipedia.org/wiki/Köppen_climate_classification
Response 7: We agree the comments and have modified the climate type according to the Köppen climate classification as suggested.
Point 8: How did you modify the Tullgren extractors? Please give a detailed explanation.
Response 8: We made a mistake here. We double checked the reference and it was the Tullgren extractors we used. This method is widely used to extract soil fauna [e.g.Wang, et al. [4], Li, et al. [5]].
Point 9: How did you define/determine the groups? Orders? Families?
Response9: In our manuscript, we defined the groups as taxonomic Orders (e.g., Hymenoptera, Diptera (larva), Collembola, etc.) according to Yin [1, 2]. We have revised the definition in the manuscript.
Point 10: Did you really identify species?
Response 10: Sorry for the confusion. The biodiversity of soil fauna communities were estimated using taxonomic Orders. So we modified relevant sentences.
Point 11: How did you identify the phytophagous fauna?
Response 11: First, we recorded all the soil fauna that we observed. Then, we determined their feeding habits based on many references, and finally picked out the group of phytophagous fauna.
Point 12: I would suggest to seperate the repeated measures anova, the two way anova and the one way anova results as the combined table is very difficult to understand. Three seperate ables would make it a lot easier. What does does Time (T) mean here? Please explain.
Response 12: We appreciate the comments and have done as suggested. Legends and orders of tables have also been revised accordingly. Time (T) means the associated variables were measured more than once. For example, soil temperature and moisture were measured once or twice (growing season) a month from January to December 2016. Litter mass was monthly collected from November to December 2016.
Reference
1. Yin, Wenying. Subtropical Soil Animals in China (in Chinese). Beijing: Science Press, 2000.
2. Yin, Wenying. Chinese Subtropical Soil Animals (in Chinese). Beijing: Science Press, 1992.
3. Raub, Florian, Ludger Scheuermann, Hubert Hoefer, and Roland Brandl. "No Bottom-up Effects of Food Addition on Predators in a Tropical Forest." Basic and Applied Ecology 15, no. 1 (2014): 59-65.
4. Wang, Shaojun, Yan Tan, Huan Fan, Honghua Ruan, and Abao Zheng. "Responses of Soil Microarthropods to Inorganic and Organic Fertilizers in a Poplar Plantation in a Coastal Area of Eastern China." Applied Soil Ecology 89 (2015): 69-75.
5. Li, Yuanyuan, Yueqin Chen, Chun Xu, Hanmei Xu, Xiaoming Zou, Han Y. H. Chen, and Honghua Ruan. "The Abundance and Community Structure of Soil Arthropods in Reclaimed Coastal Saline Soil of Managed Poplar Plantations." Geoderma 327 (2018): 130-37.
Author Response File: 
Author Response.docx
Reviewer 2 Report
The manuscript by Bian et al. presents results of an N fertilization experiment on soil microfauna in a poplar plantation on an alkaline soil in China. In general, N addition effects had minimal effects on soil litter, although depth-by-N interactions for some of the faunal measures points to complex impacts of N on fauna. These need to be clarified in the text as noted below. The manuscript is fairly well written, although there are several sections that need to be restructured as noted below.
I have marked the pdf manuscript and there are the following accompanying comments:
Paragraph L50: tense should be past
Line 57: rhizodeposition is certainly a large driver of belowground ecology, and this should be included
Line 83: these sentences should be switched in order
Line 96-97: rewrite perhaps as suggested; incomplete sentences as presented
Results Section 3.2: this section needs to be re-written to reflect the patterns in the data. No where is there a “decrease” in any of the variables except in the lower horizons. The high N additions lead to a negation of the stimulation at lower levels. To say high N reduced responses is not correct
Table 1: I am surprised there is no change in soil N. What underlies this lack of change??
Line 220: There IS a significant effect? You have stimulation, recovery, stimulation, and recovery moving down the horizon. You discuss this in the rest of the paragraph.
Table 2 or new Figure: I think it would be useful to explore the relationship between root growth parameters and soil N either as a graph or in this table
Line 258: add rhizodeposition
Line 263: lacking evidence that your soils acidified under N addition, I do not think this would be true for your soils
Section 4.2: Needs large re-write; incomplete sentences and lack of parsimony in the list. The list should start with “:” and be separated by “;” as indicated
Line 312: what does “high N depression” mean?
Line 323: sentence is redundant
Conclusions: responses returned to control levels are were not depressed. See section 3.2 comments. In addition, you have no data on air circulation and this cannot be in conclusions
Citations: several marks as noted.
Author Response
Response to Reviewer 2 Comments
General comments: The manuscript by Bian et al. presents results of an N fertilization experiment on soil microfauna in a poplar plantation on an alkaline soil in China. In general, N addition effects had minimal effects on soil litter, although depth-by-N interactions for some of the faunal measures points to complex impacts of N on fauna. These need to be clarified in the text as noted below. The manuscript is fairly well written, although there are several sections that need to be restructured as noted below.
Response : We appreciate the comments and the opportunity for us to revise. We have carefully revised our manuscript according to the following comments.
Point 1: Paragraph L50: tense should be past.
Response 1: Done as suggested.
Point 2: Line 57: rhizodeposition is certainly a large driver of belowground ecology, and this should be included.
Response 2: We appreciate the comment and we have added rhizodeposition as “especially C from the roots associated with changes in rhizodeposition”.
Point 3: Line 83: these sentences should be switched in order.
Response 3: Done as suggested in Line 87-92 on Page 2.
Point 4: Line 96-97: rewrite perhaps as suggested; incomplete sentences as presented.
Response 4: We rewrote the sentences as “The quantity and quality of food resources are likely to change in response to N addition, and then mediating the effects of N addition on soil fauna communities.” in Lines 103-106 on Page 3.
Point 5: Results Section 3.2: this section needs to be re-written to reflect the patterns in the data. Nowhere is there a “decrease” in any of the variables except in the lower horizons. The high N additions lead to a negation of the stimulation at lower levels. To say high N reduced responses is not correct.
Response 5: We agree the comments and have revised the contents to correctly reflect the patterns.
Point 6: Table 1: I am surprised there is no change in soil N. What underlies this lack of change??
Response 6: We found some researches in forests consistent with our result [1, 2]. N addition can enhance N mineralization, nitrification and denitrification [3]. Therefore, N addition could have a significant effect on available N instead of total soil N[4].
Point 7: Line 220: There IS a significant effect? You have stimulation, recovery, stimulation, and recovery moving down the horizon. You discuss this in the rest of the paragraph.
Response 7: If we understand this comment correctively: The significant effect is associated with soil depth and the interaction of N addition and soil depth rather than with N addition. In this paragraph, we described the effects of N addition (main effects, which is not significant), soil depth (main effects), and the interaction of N addition and soil depth (interactive effects) on the group number and diversity of soil fauna. The abrupt decrease at N2 is resulted from the stimulation, recovery, stimulation and recovery and discussed this in 4.2.
Point 8: Table 2 or new Figure: I think it would be useful to explore the relationship between root growth parameters and soil N either as a graph or in this table.
Response 8: We did analyse the correlation between root growth parameters and soil N. The result showed no significant correlation between them, and multifactor linear regression showed no environmental variables entering into the equation. We thus did not include them either in a figure or in a table.
Point 9: Line 258: add rhizodeposition.
Response 9: Done as suggested in Lines 288-289 on Page 13.
Point 10: Line 263: lacking evidence that your soils acidified under N addition, I do not think this would be true for your soils.
Response 10: Our unpublished pH data did show that N addition decreased pH values in the same study site. We revised as “soil acidification (unpublished data, Xu et al.)”.
Point 11: Section 4.2: Needs large re-write; incomplete sentences and lack of parsimony in the list. The list should start with “:” and be separated by “;” as indicated.
Response 11: We have clearly reconstructed these sentences.
Point 12: Line 312: what does “high N depression” mean?
Response 12: The “high N depression” referred here means negative effects of high N addition on soil fauna [4]. We rewrote as “the depression of high N addition”.
Point 13: Line 323: sentence is redundant.
Response 13: Deleted as suggested.
Point 14: Conclusions: responses returned to control levels are were not depressed. See section 3.2 comments. In addition, you have no data on air circulation and this cannot be in conclusions.
Response 14: We rewrote the sentence (to control levels) and deleted the “air circulation”.
Point 15: Citations: several marks as noted.
Response 15: We have updated and double checked the references.
1. Thomas, R. Q., G. B. Bonan, and C. L. Goodale. "Insights into Mechanisms Governing Forest Carbon Response to Nitrogen Deposition: A Model-Data Comparison Using Observed Responses to Nitrogen Addition." Biogeosciences 10, no. 6 (2013): 3869-87.
2. Wu, N., H. Qian, Y. Tan, and Y. Wang. "Effect of Nitrogen Addition on Carbon and Nitrogen Stable Isotopes in Temperate Forest Litter and Soil." Journal of Environmental Biology 39, no. 6 (2018): 1036-40.
3. Lu, Meng, Yuanhe Yang, Yiqi Luo, Changming Fang, Xuhui Zhou, Jiakuan Chen, Xin Yang, and Bo Li. "Responses of Ecosystem Nitrogen Cycle to Nitrogen Addition: A Meta-Analysis." New Phytologist 189, no. 4 (2011): 1040-50.
4. Xu, G. L., J. M. Mo, S. L. Fu, P Gundersen, G. Y. Zhou, and J. H. Xue. "Response of Soil Fauna to Simulated Nitrogen Deposition: A Nursery Experiment in Subtropical China." Acta Scientiae Circumstantiae 19, no. 5 (2007): 603-09.
5. Zhou, Danyan, Danrong Bu, Zhiwei Ge, Jing Yan, Hanran Xiao, Honghua Ruan, and Guohua Cao. "Effects of Nitrogen Addition on Soil Fauna in Poplar Plantation with Different Ages in a Coastal Area of Eastern China (in Chinese)." Chinese Journal of Ecology 34, no. 9 (2015): 2553-60.
Author Response File: Author Response.docx
