Responses of Rhizosphere Soil Chemical Properties and Bacterial Community Structure to Major Afforestation Tree Species in Xiong’an New Area
Round 1
Reviewer 1 Report
The manuscript is interesting and in line with the scope of the journal.
It requires a few additions.
· Please provide the particle size distribution of the soil used for the tests. It is necessary for the correct interpretation of the test results. Perhaps the changes in the soil microbiome were determined to a greater extent by the soil granulometric composition than by the type of stand. Therefore, the particle size distribution is necessary to correctly draw conclusions.
· In chapter "2. Materials and Methods" describe exactly how you established the "Core Tax".
· Check the nitrogen content. It's bad now. Currently, in Fig. 2 there are several times more ammoniacal nitrogen and nitrate nitrogen than total nitrogen. Additionally, your units for ammonia and nitrate nitrogen are wrongly recorded. You give them per 1 g, and it should be per 1 kg of soil. Provide a photo documenting the stand of the individual examined objects.
Author Response
Comment 1:
“Please provide the particle size distribution of the soil used for the tests. It is necessary for the correct interpretation of the test results. Perhaps the changes in the soil microbiome were determined to a greater extent by the soil granulometric composition than by the type of stand. Therefore, the particle size distribution is necessary to correctly draw conclusions.”
Response 1:
Thank you very much for your suggestion, we think it is very valuable, but for a variety of reasons, we did not conduct this experiment. First of all, according to the information provided to us by local administration, land use of studied stands were the same before large-scale afforestation, all of which were cultivated land. Moreover, studied area is not large, soil parent material, climate, and hydrology conditions in this area are consistent. We have learned through some previous studies that, the same conditions would lead to essentially the same distribution of soil particle size (Certini et al., 2022). In addition, we have read papers on the effect of land use changes on soil particle size distribution. We found that although afforestation can bring some impacts, these studies are often based on stands that have been planted for decades (Shirato et al.,2004; Li et al., 2022). While all stands in this study were only planted for three years, and were basically not disturbed by humans after planting (Delbecque et al.,2022). So we did not consider this indicator at the beginning of experimental design, but planned to carry out long-term monitoring of the stands in this area, and conduct more comprehensive work after the afforestation reaches a certain number of years. Therefore, this paper focuses on the determination of several other indicators. After reading your suggestion, we believe that it is actually reasonable to conduct research on soil particle size distribution in the early stage of afforestation. However, Covid-19 has kept resurging, due to the local policies, we are currently unable to go to studied area for sampling, so we cannot complete relevant experiments for the time being, hope you can understand. We will include this indicator in subsequent studies of this region after policy easing.
Certini, G.; Scalenghe, R. The crucial interactions between climate and soil. Sci. Total Environ. 2022, 856, 159169, doi:http://doi.org/10.1016/j.scitotenv.2022.159169.
Delbecque, N.; Ranst, E.V.; Dondeyne, S.; Mouazen, A.M.; Vermeir, P.; Verdoodt, A. Geochemical fingerprinting and magnetic susceptibility to unravel the heterogeneous composition of urban soils. Sci. Total Environ. 2022, 847, 157502, doi:http://doi.org/10.1016/j.scitotenv.2022.157502.
Li, K.; Ni, R.Q.; Lv, C.F.; Xue, L.Y.; Zhang, C.H.; Li, C.R.; Shen, W.X.; Guo, H.L.; Zhang, Y.K. The effect of Robinia pseudoacacia expansion on the soil particle size distribution on Mount Tai, China. Catena 2022, 208, 105774, doi:https://doi.org/10.1016/j.catena.2021.105774.
Shirato, Y.; Taniyama, I.; Zhang, T.H. Changes in soil properties after afforestation in Horqin sandy land, North China. Soil Sci. Plant Nutr. 2004, 50, 537-543, doi:http://doi.org/10.1080/00380768.2004.10408510.
Comment 2:
“In chapter "2. Materials and Methods" describe exactly how you established the "Core Tax".”
Response 2:
LefSe analysis conducted non-parametric factorial Kruskal-Wallis rank sum test, detecting the species with significant differences in abundance between different groups. Then Wilcoxon rank sum test was used to conduct pairwise test for subgroups in each group. Linear discriminant analysis (LDA) was applyed for data dimension reduction, and to find core taxa with statistical differences among tree species. This section has been added to line 614-619 of the manuscript.
Segata, N.; Izard, J.; Waldron, L.; Gevers, D.; Miropolsky, L.; Garrett, W.S.; Huttenhower, C. Metagenomic biomarker discovery and explanation. Genome Biol. 2011, 12, R60, doi:http://doi.org/10.1186/gb-2011-12-6-r60
Comment 3:
“Check the nitrogen content. It's bad now. Currently, in Fig. 2 there are several times more ammoniacal nitrogen and nitrate nitrogen than total nitrogen. Additionally, your units for ammonia and nitrate nitrogen are wrongly recorded. You give them per 1 g, and it should be per 1 kg of soil. Provide a photo documenting the stand of the individual examined objects.”
Response 3:
We are very sorry for the problem in Figure 2. The units of NO3-- N and NH4+-N are indeed mg·kg-1, and we have modified them for this problem. The modified part is under line 889.
We feel so sorry that we did not find relevant pictures after checking all the survey materials. We originally planned to continue sampling in Xiong’an Millennium Forest this year, supplement data and pictures, and carry out further research. However, in this special period, Tianjin and Hebei Province both suffered a relapse of Covid-19, policies of both places do not allow us to go to Xiong’an New Area for investigation. I hope you can understand and apologize again.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
The introduction section shoulbe shortened. It is too long. Also you should write aim of this study clearly. The abstract also shoulb written as an understanble more.
Author Response
Comment 1:
“The introduction section shoulbe shortened. It is too long.”
Response 1:
Thanks a lot for your suggestion, we've revised the introduction to make it more clear and concise. Introduction is mainly divided into the following parts. First, we introduce the development history of plantation and its important role. Then, by introducing the interaction between trees, soil and microorganisms, availability of evaluating afforestation effects through soil and bacterial community properties is illustrated. Finally, we give a brief introduction to studied area, from which the purpose and significance of this study are drawn.
Comment 2:
“Also you should write aim of this study clearly. The abstract also shoulb written as an understanble more.”
Response 2:
Thank you very much for your suggestion, we think that is very helpful, and we have made a clearer description of the aim. This study chose eight commonly used species in Millennium Forest, aiming to explore how tree species affect rhizosphere chemical properties and bacterial community structure, further evaluate afforestation effect of different stands. Our purpose was to provide reasonable suggestions for following afforestation, and to offer new ideas for selection of afforestation methods and tree species in north China. These modifications are in lines 254-258 of the manuscript.
Based on your suggestion, we have revised the abstract into three main sections. First, we briefly describe the scientific question to be addressed in this study and the experiments conducted to explore this question. Then we introduced the results of this paper from three aspects: the influence of tree species characteristics on rhizosphere soil chemical properties, the characteristics of rhizosphere soil bacterial communities of different tree species, and the effect of soil chemical properties on bacterial communities. Finally, we point out the tree species suitable for afforestation in this area through the research results, and put forward some reasonable suggestions for the implementation of following afforestation plan. We have also revised some misleading statements to make them clearer and easier to understand.
Author Response File: Author Response.pdf
Reviewer 3 Report
Dear Authors,
The manuscript “Responses of Rhizosphere Soil Physicochemical Properties and Bacterial Community Structure to Major Afforestation Tree Species in Xiong’an New Area” is an interesting paper for readers about relationship between soil chemical properties and bacterial community structure under different forest tree species. Please consider some small point as belove:
- Please short introduce the information about year of your forest study: when it was planted, how to management?
- Short provide the method used to analyse available P (name of method or extraction)?
- The word “physicochemical” is used in the title and in the content of paper. However, the parameters in paper are TC, TN, AP,… soil moisture. I think we should use “chemical properties”.
- I think it is a interesting view if you analyse the relationship between soil moisture and NH4+, or pH and NH4+ because the location in your study had very high in pH values.
Author Response
Comment 1:
“Please short introduce the information about year of your forest study: when it was planted, how to management?”
Response 1:
All stands studied were planted in spring 2018 and they had been planted for 3 years at the time of sampling. Xiong’an Millennium Forest adopts the concept of “close-to-natural” management. The managers hope to realize the self-regulation, self-renewal and self-succession of the stands through this management method. Therefore, all stands have not been thinned, and no chemical fertilizers have been applied, there was no human interference too. The above content is on line 279-280 and 543-545 of the manuscript.
Comment 2:
“Short provide the method used to analyse available P (name of method or extraction)?”
Response 2:
The analyse method we use for available phosphorus (AP) was molybdenum antimony anti-color spectrophotometry. The abovecontent is on line 587-589 of the manuscript.
NY/T 1121.7-2014; Soil testing-Method for determination of available phosphorus in soil. Ministry of Agriculture, PRC: Beijing, China, 2014
Comment 3:
“The word “physicochemical” is used in the title and in the content of paper. However, the parameters in paper are TC, TN, AP,… soil moisture. I think we should use “chemical properties”.”
Response 3:
After discussion, we think that your proposal is very rigorous and have made relevant modifications throughout the manuscript.
Comment 4:
“I think it is a interesting view if you analyse the relationship between soil moisture and NH4+, or pH and NH4+ because the location in your study had very high in pH values.”
Response 4:
Thank you very much for your advice. We have reanalyzed the data and found that NH4+-N concentration is indeed significantly correlated with both SM and pH. Ammonium nitrogen, an important form of mineral nitrogen in alkaline soils in northern China, its main source is the mineralization of soil organic nitrogen by microorganisms such as ammoniation. This process is largely affected by soil moisture, pH, nutrient content and soil microbial properties (Shi et al., 2020). Through previous studies, we know that when soil moisture and temperature are both low, mineralization rate will slow down, resulting in the decrease of NH4+-N concentration in soil, which may explain the result that both NO3--N and NH4+-N concentrations are positively correlated with SM in this paper (Hu et al., 2008).
In addition, some studies have shown that, organic acids released by root exudation and litter decomposition make soil acidification aggravated with extension of afforestation years (Huang et al., 2022). And it is generally believed that soil acidification is mainly related to excessive application of nitrogen fertilizers (Guo et al., 2010). Nitrogen fertilizer will be converted into nitrate nitrogen in soil, loss of nitrate nitrogen will take away a large amount of calcium, magnesium and other ions, which may lead to soil acidification. While this is also reflected in the inverse ratio of NH4+-N concentration to pH. Studied area was located in Beijing-Tianjin-Hebei region with severe soil salinization. Besides, the afforestation period was short, and no nitrogen fertilizer was applied after afforestation, we thought this might be the reason why soil of studied stands maintained high pH. The above content is on line 1072-1079 and 1104-1107 of the manuscript.
Guo, J.H.; Liu, X.J.; Zhang, Y.; Shen, J.L.; Han, W.X.; Zhang, W.F.; Christie, P.; Goulding, K.W.T.; Vitousek, P.M.; Zhang, F.S. Significant acidification in major Chinese croplands. Science 2010, 327, 1008-1010, doi:http://doi.org/10.1126/science.1182570.
Hu, L.; Li, X.Q.; Huang, D.K.; Cheng, J.Z. Ammonium nitrogen in surface soil of arid and semiarid Central East Asia. Geochimica 2008, 37, 572-580, doi:http://doi.org/10.19700/j.0379-1726.2008.06.007.
Shi, X.; Li, Y.H.; Li, F.D. Variation characteristics and influencing factors of soil ammonium nitrogen and nitrate nitrogen in cotton fields in different irrigation districts of Manas river basin. Acta Sci. Natur. Univ. Sunyatseni 2021, 60, 80-90, doi:http://doi.org/10.13471/j.cnki.acta.snus.2020.07.29.2020d032.
Huang, X.Z.; Cui, C.; Hou, E.Q.; Li, F.B.; Liu, W.J.; Jiang, L.F.; Luo, Y.Q.; Xu, X.N. Acidification of soil due to forestation at the global scale. Forest Ecol. Manag. 2022, 505, 119951, doi:https://doi.org/10.1016/j.foreco.2021.119951.
Author Response File: Author Response.pdf
