Effects of Poplar Shelterbelt Plantations on Soil Aggregate Distribution and Organic Carbon in Northeastern China
Round 1
Reviewer 1 Report (Previous Reviewer 2)
The paper entitled “Effects of Poplar Shelterbelt Plantations on Aggregate Distribution and Organic Carbon in Northeastern China” aimed to determine the distribution, stability, and soil organic carbon of aggregate, examine the contribution of soil aggregate proportion, stability index, and aggregate-associated soil organic carbon to the total soil. The results may useful fir the local managers.
How do you choose the plots? You must clarify
How did you sample soil?
Line 146: You divided soil samples to two part, so how many samples used for passing through a 025 mm and how many samples used for analyzing the proportion of soil aggregates?
Line 195-203: It is not clear. Rewrite the paragraph.
The results were not written in good format. It is misunderstanding.
Line 282-283: the tables are a part of figure 7? If yes, you must show it in the figures. If not you must number it as a table and discuss about it.
Author Response
Thank you for your suggestion. Please check the attachment for a detailed response.
Author Response File: 
Author Response.pdf
Reviewer 2 Report (Previous Reviewer 1)
Effects of Poplar Shelterbelt Plantations on Aggregate Distribution and Organic Carbon in Northeastern China, By Yan Wu et al.
Unfortunately at the second round of evaluation, the manuscript did not improve up to accepting level. The comments were not addressed adequately.
1. Repeating descriptions in Results and Discussions still a major weakness of manuscript. Here I mentioned two examples below. In whole discussion many information have been given in same format as already mentioned in results section (even with reference of Table and Figure which already describe in results section). Generally, Discussion should contain critical explanation of results, why this was happened? What other researchers found and what is the impacts of this results etc.
In Results: R0.25, MWD, and GMD significantly increased in the 0–20 cm soil layer following afforestation (P<0.05) (Fig. 3) but the differences were not significant in other four soil layers between poplar shelterbelt and farmland. (Line 211-114)
In Discussion: However, significant difference s in aggregate distribution, R0.25, MWD, and MGW were observed only in the 0 –20 cm depth, no remarkable differences in 20 –40 cm, 40 –60 cm, 60 –80 cm and 80 –100 cm (Figs. 2 and 3) (311-314)
In Results: The SOC stock in total soils were more dependent on the SOC stocks in >2 mm and 0.25–2 mm (R2 = 0.87, R2 277 = 0.81) aggregates than on those in the 0.25–0.053 mm and <0.053 mm (R2 = 0.77, R2 278 = 0.68) aggregates (Fig. 7) (Line 275-277)
In Discussions: Our studies underlined that the SOC stock in total soils was more dependent upon the SOC stock in >2 mm (R2 = 0.87) and 0.25–2 mm (R2 364 = 0.81) aggregates than on those in the 0.25–0.053 mm (R2 = 0.77) and <0.053 mm (R2 365 = 0.68) aggregates (Fig. 6) (Line 363-366).
2. Results still incorrect:
As per previous comments on total SOC content, Line 307-310 has been corrected but partially. “In this study, poplar shelterbelt increased SOC in 0– 20 cm (Fig. 4)”. (Line 4). Is this SOC content or stock? In results “However, the changes in shelterbelt-induced SOC concentration significantly increased by 13.3% in the 0–20 cm depth (P<0.05) (Fig. 4), with no significant differences in the other four layers. (Line 226-228). According to data in Figure 4, no significance difference in SOC content or SOC stock at 0-20 cm between poplar and farmland (???).
1) Proportion of > 2mm (%) at 0-20cm in Figure 2 and SOC stock in 0.053-0.025mm aggregates 0-20 cm depth in Figure 6 seem not significantly differ but considered as so. Please check.
2) Some graphs have a. b other have ** for significant differences.
Table 1 is missing (?????)
3. English language correction not still due.
From the Title of manuscript not clear about soil C or forest C
Line 65 “an critical role”
Author Response
Thank you for your suggestion. Please check the attachment for a detailed response.
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report (Previous Reviewer 2)
The paper "Effects of Poplar Shelterbelt Plantations on Soil Aggregate Distribution and Organic Carbon in Northeastern China" improved significantly and acceptable in this format. Good job!
Author Response
Thank you for your recognition and we will continue our work..
Author Response File: Author Response.pdf
Reviewer 2 Report (Previous Reviewer 1)
Fig 4. SOC concentration 0-20cm, error bars showed changes between poplar and farmland are not singnifiant but in per cent change line put * which means significant. Please check.
Table 1 & 2 : Titles need to rewrite (Table 2 concentration (stock)????, in column 1, "SOC content" "in total soil" are not clear, please rewrite correctly). In text no mention of Table 1. Information in Table 1 must be initial information as C concetration were 7-11 g/kg (but in Figure 4 these are 16-18 g/kg), so it should be mentioned in the Title of Table 1.
Author Response
Thank you for your suggestion.
Author Response File: Author Response.pdf
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
Effects of Poplar Shelterbelt Plantations on Aggregate Distribution and Organic Carbon in
Northeastern China, By Yan Wu et al.
In this manuscript the authors report the findings on soil organic C concentration and stocks in soil aggregates under two land-use types (cropland and forest plantation) in Central Songnen Plain, China. The topic is certainly interesting as the authors tried to investigate the effects of afforestation on physical stability of SOC in agricultural landscape and the studies and its findings might be of interest to the readers of forests.
This type of study needs a comprehensive approach to explore the real contribution of afforestation on SOC distribution in different aggregates sizes. Because how much organic matter and mycorrhizal hyphae/fine roots really added to soil during last 40 years from poplar and maze cultivation systems, are the main determinants of aggregate formation and subsequent occlusion of organic C in it. Followings are major comments, that need to be addressed:
1. Soil of adjacent farmland, which was under continuous management practices since planation established, was considered as “control” to compare with plantation soils. This approach is not appropriate because difference in aggregates between farmland and planation soils can be attributed to soil degradation in farmland due to 40 years of cultivation and other management activities. In such case we generally use adjacent undisturbed, fellow plots as “control”.
2. In introduction, there is nothing about (no literature review) MWD, MGD, D etc. Also need justification of three aggregate sizes in Hypothesis 1 & 2 (why these sizes are containing higher/lower SOC- review from literature).
3. It is also necessary to look at the soil properties related to aggregate formation and C stabilization, i.e. soil texture, soil pH, Ca and Na etc. From the site map (Fig-1), the distance between two location is more than 80 km, therefore it is necessary to include a Table containing soil properties of three sites.
4. Repeating description should be avoided (Line 192-197), same figure (Fig 3) was described twice. Many facts and figures were repeated both in results and discussions sections. For examples: In discussions section (Line 317) “Our results indicate that shelterbelt enhances SOC concentration and stock by 21.5% and 18.7%, respectively, in >2 mm and 0.25–2 mm soil aggregates in the 20–40 cm depth (Fig. 5,6)”. This information was already mentioned in results section (Line 224 & 237).
5. In the discussions section findings were explained by increased litter-inputs (Line 218-287, 300) by afforestation, where as the results showed no increased in SOC due to afforestation (Line 207-208). This type of contradiction should be removed.
6. The authors estimated concentration and stock of SOC in different aggregates sizes at different soil layers. It is not clear how the authors determined C stock in aggregate fractions, as it was mentioned only about one part of dried sample (Line 132).
7. There are many English language errors in the manuscript and need thorough revision by qualified person. The followings are some confusing/ inappropriate phrases used in the manuscript:
1. “-------- and SOC in to total SOC.” (Line 14)
2. “-------the same research conditions---” (Line 119)
3. “---be discovered-----” (Line 121 & other places)
4. “ ---- mowwing---” (Line 131)
5. Total sample number should be 360 (3 sites x 12 pairs x 2 profiles x 5 layers) not 180, because each pair has two profiles (Line 129).
6. “---cutting ring -------” (Line 134)
7. “—level of criterion---” (Line 175)
8. “----was more relied---” (Line 293)
9. “------ land type changes---" (Line 352)
Reviewer 2 Report
1. Line 52: Give a explicit to SOC
2. The language and grammar of the paper must revise.
3. Line 105-106: what is typical black soils? Use international classification like USDA.
4. Replace all figures with high resolution one. The quality of all figures are poor.
5. Line 148: Give explicit to the abbriviations
6. In figures, it was written that “The different letters denoted significant difference between 221 shelterbelt plantation and farmland at same soil layer”. I am not able to see the letters. Complete the figures and replace with high resolution ones.
7. Fig 7: Instead of using right and left use (a) and (b). Also, it is better to have equations in table not in the figure.
8. The discussion must be written stronger and have good discussion for the result which is weak in your manuscript.
9. Actually, the novelty of your study is not clear.
The paper needs major revision and extensive editing of English language and style required. The result and discussion section must be improved. The quality of the figures are low and must replace with high quality ones.
