Review Reports

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The manuscript addresses a relevant topic, but several methodological and statistical issues need clarification. Please see the detailed comments in the attached review report.

Comments for author File: Comments.pdf

Comments on the Quality of English Language

The manuscript is generally understandable, but some sentences would benefit from language editing for clarity and precision.

Author Response

Major Comments 
Comment 1: The experimental design is not entirely clear. The authors indicate that each 
treatment had three biological replicates, while three quadrats were also sampled within each 
plot. Please clarify what was considered the experimental replicate in the statistical analysis 
and how the three quadrats were handled. This point is important to ensure that subsamples 
were not treated as independent replicates.
Comment 3: More details about the fertilizers would help the reader understand the 
comparison between the two treatments. While the N:P₂O₅:K₂O ratio is given for the chemical 
fertilizer, the nutrient composition of the organic fertilizer is not reported. Please provide its 
N, P, and K contents, as well as the timing and frequency of fertilizer application. 
Revisions were made as follows in response to Comment 1 and Comment 3 of the main comments:

2.2. Experimental design

Three experimental sites were selected in the middle section of the Greater Khingan Mountains (Keyouqian Banner, Keyouzhong Banner, and Zhalaite Banner). At each site, three treatments were established: fencing enclosure (control, CK), fencing enclosure + chemical fertilizer (CF), and fencing enclosure + organic fertilizer (OF). Each treatment had three biological replicates, with each replicate consisting of one experimental plot of 25 m². Organic fertilizer was applied at 2000 kg hm⁻² (N+P₂O₅+K₂O ≥ 8.5%；Organic matter ≥ 45%；Humic acid ≥ 20%；Amino acid ≥ 10%；Beneficial microorganisms ≥ 2.0 × 10⁸ CFU g⁻¹), and chemical fertilizer was applied at 1050 kg hm⁻² (nutrient ratio N:P₂O₅:K₂O = 26:11:11).Fertilization was performed in late May, once per year. The fertilization rate and frequency were based on the conventional fertilization rates and frequencies used for local crops.

Comment 2: The study was conducted in 2021 and 2022, but it is not clear how the year 
effect was considered in the analysis. Please explain whether data from the two years were 
pooled, averaged, or analyzed separately. Given the structure of the experiment, the authors 
should also consider whether treatment, region, year, and their interactions need to be included in 
the statistical model. 
Response to this point:
The data from the two years were pooled for analysis. This experiment included three fertilization treatments and three regions, which allowed a two-factor experimental design to be constructed. Due to climatic influences, the data exhibited a certain degree of interannual fluctuation. To make the data relatively stable, we decided to pool the data from the two years. When the data were analyzed separately by year, the considerable climatic differences among years and regions—especially the marked interannual variation in climate—led to substantial discrepancies in the data. The unpooled data exhibited relatively weak central tendency, whereas pooling better reflected the central tendency of the data. The ANOVA performed on the pooled dataset was essentially based on a block design; in other words, this experimental design facilitated redundancy analysis and made it easier to reveal the patterns of fertilization effects.

Comment 4: Some important details of the soil analyses are missing. For example, the soil
to-solution ratio and solution used for pH measurement should be reported. The extraction 
method used to determine available phosphorus should also be clearly stated. Please also 
clarify whether soil samples collected from the three quadrats were analyzed separately or 
combined before analysis.
Response to Opinion 4 in the Main Opinions shall be provided together with Opinion 4 and Opinion 5 in the Specific Opinions.

Comment 5: The discussion suggests that chemical fertilization relieved N limitation and 
subsequently made P the main limiting nutrient. This is an interesting explanation, but the 
current measurements do not directly demonstrate such a shift in nutrient limitation. I suggest 
presenting this as a possible mechanism rather than a firm conclusion. 
Revised as follows:
This study found that chemical fertilizer application significantly reduced soil available phosphorus content (P < 0.05), a phenomenon consistent with the observations of Yang et al. [24], who reported that chemical fertilizer inputs can simultaneously increase vegetation biomass and decrease soil available phosphorus. The underlying mechanism is that nitrogen is one of the primary limiting factors for plant growth [25]. Chemical fertilizers rapidly supply high concentrations of inorganic nitrogen to the soil, effectively alleviating nitrogen limitation and promoting rapid plant growth. During this process, the rate of phosphorus uptake and utilization by plants increases substantially, while soil phosphorus fixation is intensified, ultimately leading to a decline in soil available phosphorus content [26,27]. Combined with the correlation analysis under the chemical fertilizer treatment in this study (Figure 3a), aboveground biomass was significantly positively correlated with soil available phosphorus (P < 0.05). It is therefore speculated that the nutrient limiting factor in the grassland system may also have shifted after chemical fertilizer input in this study. Once nitrogen becomes sufficient, phosphorus may become the new growth-limiting factor; plants consume large amounts of soil available phosphorus to support biomass accumulation, resulting in decreased soil available phosphorus content and significantly increased aboveground biomass.

Comment 6: Please provide more information on the correlation analysis, particularly the
type of correlation used and the number of observations included. The use of correspondence analysis also needs some justification, given the nature of the variables included. In addition, the proximity of variables and treatments in the ordination plot should not by itself be interpreted as evidence that a treatment directly “drives” or “regulates” biomass.
Revise as follows:

2.4. Data analysis

One-way analysis of variance (ANOVA) was performed among treatments using SPSS 20.0. Pearson correlation analyses were conducted separately for different treatments and different plots. Correspondence analysis (CA) was employed across different regions to visualize the multivariate associations among treatments, aboveground biomass, and soil properties. Correlation heatmaps and correspondence analysis plots were generated using Origin 2024 Pro and R 3.3.1 to systematically examine the differences and intrinsic relationships among vegetation characteristics, soil nutrients, and grassland aboveground biomass under different experimental treatments.

3.5. Correspondence analysis of grassland aboveground biomass and soil nutrient indicators under different fertilization treatments in each region

Correspondence analysis results of grassland aboveground biomass and soil nutrient indicators under different fertilization treatments in each study region are presented in Figure 5. The indicators displayed distinct distribution patterns in the two-dimensional ordination space, indicating that different fertilization treatments not only altered soil nutrient contents but also regulated the association structures among indicators of the soil–vegetation system.

In the Keyouqian Banner site (Figure 5a), soil organic matter, soil available phosphorus, and soil pH clustered relatively closely in the ordination space, indicating strong associations among these indicators. In contrast, although soil alkali-hydrolyzable nitrogen showed an overall distribution direction consistent with the above indicators, its relatively greater spatial distance suggested a relatively weak association. These soil indicators were generally located close to the organic fertilizer treatment in the ordination space, indicating that their changes had a relatively strong association with the organic fertilizer treatment. Soil available potassium was relatively independent and located close to the chemical fertilizer treatment, reflecting that its variation pattern had a relatively high consistency with the chemical fertilizer treatment. In addition, aboveground biomass was closer to the control treatment in the ordination space, indicating that in the Keyouqian Banner site, the association between aboveground biomass and fertilization treatments was relatively weak. The separation of different fertilization treatments in the ordination space indicated that the soil nutrient response patterns corresponding to different fertilization methods differed to some extent.

In the Keyouzhong Banner site (Figure 5b), soil alkali-hydrolyzable nitrogen, soil available potassium, and pH clustered relatively closely, reflecting strong associations among the three; soil organic matter and soil available phosphorus also exhibited a relatively high degree of clustering, indicating a strong association between the two. Although the two groups of indicators formed separate clusters, a certain spatial distance remained between the groups, indicating that their mutual association was relatively limited. Aboveground biomass was relatively close to both the chemical fertilizer and organic fertilizer treatments in the ordination space, indicating that under the conditions of this experiment, fertilization treatments had a relatively strong association with changes in aboveground biomass.

In the Zhalaite Banner site (Figure 5c), soil alkali-hydrolyzable nitrogen, soil available phosphorus, soil available potassium, and soil pH clustered relatively closely in the ordination space, indicating strong associations among these indicators. Soil organic matter was generally consistent with the distribution direction of the above indicators, but its relatively greater spatial distance indicated a relatively weak degree of association. Aboveground biomass was located near the chemical fertilizer and organic fertilizer treatments, indicating that under the conditions of this experiment, changes in aboveground biomass exhibited a relatively strong association with fertilization treatments.

Comment 7: The three study sites differ not only in soil properties but also in elevation,
precipitation, soil type, and other environmental conditions. Since each region appears to be represented by one site, it is difficult to attribute the observed differences specifically to soil conditions. This limitation should be acknowledged, and the management recommendations should be stated with appropriate caution.
Add at the end of the discussion:
In addition, although soil properties were strongly associated with differences in aboveground biomass among regions, the three study regions differed not only in soil properties but also in elevation, precipitation, soil type, and other environmental conditions. This study was unable to fully disentangle the independent contributions of soil factors and other environmental factors to vegetation productivity. Future studies should incorporate variables such as climate, topography, and long-term changes to further clarify the relative roles of different environmental factors in driving changes in grassland productivity.


Specific Comments 
Introduction 
Comment 1 – Lines 64–69: The statement that comparisons between organic and chemical 
fertilizers are still lacking is rather broad. The authors should define this research gap more 
clearly. Is this lack of information specific to the study region, to degraded grasslands, or to 
similar grassland ecosystems? 
Revised as follows:
To date, existing research has not yet systematically compared the restoration efficacy of organic versus chemical fertilizers on degraded grasslands, nor has it thoroughly investigated whether the restoration effects of a given fertilizer type vary regionally across different degraded grassland types. It is widely assumed that chemical fertilizers produce rapid but short-lived effects, whereas organic fertilizers exert more stable but slower-acting effects. However, whether this assumption holds for all degraded grassland types remains uncertain, and it still lacks sufficient experimental validation.

Comment 2 – Lines 73–84: The objectives of the study are clear, but the expected responses 
are not stated. Adding one or two hypotheses at the end of the Introduction would help the 
reader better understand what the study aims to test. 
Revised as follows:
This study investigated the effects of fencing enclosure + chemical fertilizer application, fencing enclosure + organic fertilizer application, and fencing enclosure control on aboveground biomass and soil nutrient characteristics in three natural grasslands with contrasting soil conditions in the middle section of the Greater Khingan Mountains. Specifically, we evaluated the effects of different fertilization regimes on vegetation productivity and soil nutrient status, and analyzed the correlations between soil properties and aboveground biomass. We hypothesized that (1) both chemical and organic fertilizers would increase aboveground biomass by alleviating nutrient limitations, but would differ in their effects on soil nutrient characteristics due to contrasting nutrient release patterns; and (2) because of differences in background soil conditions among study sites, the magnitude of biomass and soil responses to fertilization would vary among study sites. These results will contribute to a better understanding of the response patterns of the grassland–soil system to different fertilization measures and provide a reference for site-specific grassland management in this region.

Materials and Methods

Comment 3 – Lines 88–104: Please indicate the soil classification system used to describe
the soils as “chernozem,” “saline-alkali soil,” and “chestnut soil.” This information would be useful, particularly for readers who are not familiar with the local soil classification.
Revise as follows:

The experimental site in Keyouqian Banner (HRQ) is located in Manzutun Manchu Township, Keyouqian Banner, Hinggan League, Inner Mongolia Autonomous Region (120°58′25.46″ E, 46°27′2.17″ N), at an elevation of 719 m. The region has a temperate continental monsoon climate, with a mean annual temperature of 4 °C, a frost-free period of approximately 100 d, and mean annual precipitation of 410–440 mm. The soil type is chernozem(Exhibiting relatively high organic matter content and favorable soil structure).

The experimental site in Keyouzhong Banner (HRZ) is situated in Daiqintala Sumu, Keyouzhong Banner, Hinggan League, Inner Mongolia Autonomous Region (121°32′16.19″ E, 45°08′9.39″ N), at an elevation of 273 m. It also experiences a temperate continental monsoon climate, with a mean annual temperature of 4.8 °C, a frost-free period of approximately 120 d, and mean annual precipitation of 370–380 mm. The soil type is saline-alkali soil(Soils characterized by salt accumulation and sodium ion enrichment, with a relatively high pH).

The experimental site in Zhalaite Banner (ZHQ) is located in Tumuji Town, Zhalaite Banner, Hinggan League, Inner Mongolia Autonomous Region (122°58′45.10″ E, 46°9′49.26″ N), at an elevation of 163 m. The climate is temperate continental monsoon, with a mean annual temperature of 4.3 °C, a frost-free period of approximately 130 d, and mean annual precipitation of 350–400 mm. The soil type is chestnut soil(Characterized by a certain level of organic matter and carbonates.


Comment 4 – Lines 117–118: It is not clear whether aboveground biomass refers to fresh or
dry biomass. Please clarify this point. If dry biomass was measured, the drying temperature and duration should also be given.
Comment 5 – Lines 113–125: Soil moisture was measured according to the Methods, but I
could not find these data in the Results. Since moisture may influence plant growth and nutrient availability, please either present these results or explain why this variable was not included in the analysis.
The above two points respond together:
Field sampling was conducted in August 2021 and August 2022, with new quadrats randomly established each year. Within each experimental plot, three standard 1 m × 1 m quadrats were randomly established. Following vegetation community surveys, soil samples from the 0–20 cm layer were collected from each quadrat, and vegetation and soil indicators were measured concurrently using the following methods: Aboveground biomass: samples were brought back to the laboratory, dried at 105 °C for 30 min to deactivate enzymes, and then further dried at 65 °C for 24 h until constant weight; Soil pH: measured with a pH meter at a soil-to-water ratio of 1:5 using distilled water; Soil organic matter: determined by the potassium dichromate (K₂Cr₂O₇) volumetric method with oil-bath heating; Soil alkali-hydrolyzable nitrogen: measured by the diffusion absorption method; Soil available phosphorus: determined by the molybdenum–antimony anticolorimetric method; Soil available potassium: extracted with ammonium acetate and measured by flame photometry. Soil samples collected from the three quadrats were analyzed separately.

Results
Comment 6 – Figure 1: Since the number of biological replicates is relatively small, showing
the individual data points together with the mean ± SE would help the reader better assess the variability within each treatment.
Reply to this point:
We combined the data from 2021 and 2022 in this study. There were three biological replicates each year, yielding a total of six replicates for the two years combined. The data exhibited certain fluctuations due to interannual variations in temperature and precipitation. We combined the two-year dataset to reduce the influence of such climatic fluctuations and obtain relatively stable data.

Comment 7 – Lines 203–217 / Figure 4: The negative relationship between AGB and alkali
hydrolyzable N in Keyouqian Banner is worth discussing in more detail. This result is not immediately intuitive and may reflect the influence of other soil properties rather than a simple relationship between N availability and biomass.
Answer together with Opinion 9 and Opinion 10 discussed in the same session.

Discussion
Comment 8 – Lines 274–286: This paragraph repeats several findings already reported in the
Results. It could be shortened, with more emphasis placed on explaining why the two fertilizer types produced similar biomass responses and how these findings compare with previous studies.
Revised as follows:
4.1. Effects of different fertilization treatments on grassland aboveground biomass and soil nutrients
Fertilization is an effective means of enhancing grassland productivity and improving soil nutrient status. Both chemical and organic fertilizers can promote vegetation recovery in grasslands, and although their modes of action differ markedly, their short-term promoting effects are similar. Consistent with the findings of Tong Z et al. [17], Li Fan et al. [18], and E. T. Borer et al. [19], chemical fertilizer can significantly increase grassland aboveground biomass (P < 0.05). Similarly, consistent with the results of Ma K et al. [20], Zhang Chu et al. [21], and Zhang Fengge et al. [22], the application of organic fertilizer can also significantly enhance grassland aboveground biomass (P < 0.05). The conventional perception that chemical fertilizers act quickly while organic fertilizers act slowly is not correct. Based on the results of this study, the effective nutrients ultimately obtained by plants under chemical and organic fertilizer applications may be similar, a view that is also supported by the findings of Lin et al. [23].

Comment 9 – Lines 327–342: The discussion of soil pH is somewhat too general. A lower
pH does not always correspond to greater nutrient availability. I suggest relating this discussion more closely to the pH values actually observed at the three study sites.
Comment 10 – Lines 335–337: The description of alkali-hydrolyzable N needs some 
attention. It should not be presented as equivalent to ammonium and nitrate, since it 
represents an operationally defined soil N fraction determined by the analytical method used.
The above two points respond jointly:

Soil organic matter releases organic acids and carbon dioxide during decomposition, thereby lowering soil pH and alleviating soil alkalization^[30]. A slightly acidic to neutral soil environment can effectively activate fixed phosphorus, reduce the adsorption and fixation of potassium by clay minerals, and substantially enhance soil phosphorus and potassium availability ^[31]. In addition, soil alkali-hydrolyzable nitrogen is mainly derived from the mineralization of organic matter; a higher organic matter content can maintain a sustained nitrogen supply potential and is compatible with a lower soil pH environment ^[32,33]. Appropriate pH conditions can activate soil microbial activity ^[34], accelerate organic matter decomposition and nutrient mineralization, and promote the transformation of organic nitrogen into plant-available alkali-hydrolyzable nitrogen, thereby increasing the alkali-hydrolyzable nitrogen content and further enhancing the level of soil available nutrients ^[35]. Conversely, high-pH, strongly alkaline soils can significantly inhibit microbial activity and nutrient mineralization processes, reduce soil potassium and phosphorus availability, and constrain the soil nutrient supply capacity ^[32,36]. The differences in soil physicochemical indicators among the three regions in this study were highly consistent with the above patterns. As shown in Figure 1, different treatments did not significantly change soil pH (P > 0.05). As shown in Figure 2, soil pH in Keyouqian Banner was significantly lower than that in Keyouzhong Banner (P < 0.05), and soil pH in Keyouzhong Banner was significantly lower than that in Zhalaite Banner (P < 0.05). As shown in Figure 2, aboveground biomass in Keyouqian Banner and Keyouzhong Banner was significantly higher than that in Zhalaite Banner (P < 0.05). Meanwhile, the negative correlation between aboveground biomass and alkali-hydrolyzable nitrogen in Keyouqian Banner (Figure 4) may be attributable to the stronger uptake of soil alkali-hydrolyzable nitrogen by the higher biomass in this region, thereby reducing the residual alkali-hydrolyzable nitrogen content in the soil.In summary, fertilization treatments did not alter soil pH; slightly acidic, low-pH soil environments are more conducive to nutrient activation and accumulation ^[37], whereas alkaline, high-pH environments impede nutrient transformation and reduce soil fertility ^[38].

Conclusions
Comment 11 – Lines 368–386: The Conclusions could be more focused on the main findings
obtained from the experiment. Some of the practical implications go beyond the variables directly measured in this study, so I suggest keeping these recommendations more closely linked to the observed biomass and soil responses.
Revise as follows:

Both chemical and organic fertilizers significantly increased grassland aboveground biomass (P < 0.05), yet their effects on soil nutrient dynamics differed. Chemical fertilizer rapidly alleviated nitrogen limitation, stimulating an increase in aboveground biomass; plants consumed substantial amounts of soil available phosphorus to support biomass accumulation, potentially leading to a decrease in soil available phosphorus content. In contrast, organic fertilizer, through slow nutrient release, maintained grassland productivity while not causing substantial accumulation of soil available nutrients.

Grassland aboveground biomass exhibited significant regional differences (P < 0.05), which largely reflected differences in soil background conditions. In Keyouqian Banner, relatively lower soil pH and higher contents of soil organic matter and available nutrients indicated superior soil conditions and higher grassland productivity. In comparison, Keyouzhong Banner and Zhalaite Banner had stronger soil alkalinity and lower background fertility, and their biomass exhibited a more pronounced response to fertilization. These results indicate that soil background conditions significantly influence fertilization effects and should be taken into account when interpreting the vegetation and soil response characteristics of different grassland regions.

References
Comment 12: Some of the references used to explain soil nutrient processes are relatively old. I suggest adding recent studies where relevant, especially those dealing with fertilization and nutrient dynamics in grassland soils.
Response to this point:
The literature has been updated with recent studies added.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

1. The abstract clearly states the research problem, experimental options, main results and practical conclusion. However, the abstract is currently too descriptive and in places draws conclusions that are not fully supported by the presented results. The transition from the established correlational or regional differences to causal statements about the factors determining productivity is particularly problematic. The first sentence is very long and loaded with information. In addition, the wording “regional environmental differences” is quite broad, although later it mainly refers to soil properties.
   From a scientific point of view, the objective should accurately reflect what was actually studied: the effect of fertilization on aboveground biomass and soil nutrient indicators and the differences in these indicators between regions.
   The biggest shortcoming of the methodological part of the abstract is that there is almost no information about the experimental design of the study.
   
   
2. The introduction should more clearly justify the relevance and scientific issues of the topic under consideration. At present, it is not sufficiently clear what specific scientific problem is being solved, what relevance this problem has for the natural grasslands of the Greater Khingan Mountains region, and what research gap it aims to fill. The research objective is also not clearly formulated. It is recommended to consistently move from the general context of the problem to the specific scientific gap, justify the necessity of studying fertilization and regional soil conditions, and clearly and unambiguously formulate the research objective. The objective should directly reflect the factors studied, the indicators evaluated, and their interrelationships. In addition, it would be appropriate to clearly identify the research hypotheses or research questions to make it easier to assess whether the selected methods and the presented results allow answering the raised problem.
   

   2. Experimental design.
   Three variants are specified – control, chemical fertilizers and organic fertilizers – and three biological replicates. However, the wording “fencing enclosure (control)” raises doubts about the control variant. All variants, as understood from the description, were fenced, therefore it should be clearly explained whether the control was only a fenced area without fertilization, or whether there was also an unfenced control. This is important, because fencing itself can affect vegetation biomass.

   It is also unclear how the experimental plots were arranged: whether their locations were selected randomly, or whether a block experimental design was used. A plot layout diagram should be provided or at least the randomization principle should be described. The methodology section needs to be significantly supplemented and refined, primarily in terms of experimental design, fertilization time and rates, statistical model, biological replicates, and sample preparation. At present, it is not sufficiently clear what the actual experimental unit is and whether the chosen statistical analysis corresponds to the study structure. It is particularly important to resolve the issue of possible pseudoreplication and justify the use of one-way ANOVA when the study compares three regions, three fertilization options, and two-year data. Without these refinements, the statistical validity of the results and the repeatability of the study are not sufficiently assured.

3. Results. This section clearly shows that both mineral and organic fertilizers significantly increased aboveground biomass, but no significant difference was found between these two fertilization options. This is an important main result of the study. It is also properly highlighted that mineral fertilizers significantly reduced the amount of available phosphorus, while other assessed soil indicators did not change significantly.

   However, the presentation of the results is mainly limited to statements about statistical significance. Actual indicator values, their percentage change, or other quantitative parameters are missing. P values ​​alone do not allow for an assessment of the biological or practical magnitude of the differences found. It is recommended to provide at least the averages of the main results and their changes in the text, especially aboveground biomass and available phosphorus.

   It should also be clarified whether the data presented for 2021 and 2022 were combined. Since the study was conducted over two years, the results section should clearly show whether there were significant differences between years and how the year factor was taken into account in the statistical analysis. The main limitation is that the results are insufficient to support the claims made in the abstract and conclusions that soil pH and nutrient status "control" aboveground biomass or that productivity increases in different regions are more dependent on fertilization. This would require additional statistical analysis, especially the assessment of the interaction between region and fertilization.
   4. 

   The conclusions clearly summarize the main results of the study, but their current formulation is too categorical and in places goes beyond the limits of the study data. Causal claims about the mechanisms of action of fertilizers, the impact of soil properties and recommendations for grassland restoration are particularly problematic.

   1. The first conclusion is not fully supported by the studies.

   The claim that chemical fertilizers:

   “rapidly supplied nitrogen to relieve nutrient limitation”

   is not directly proven by the results presented. The study found an increase in aboveground biomass, but it was not shown that the rapid supply of nitrogen was the mechanism for this change.

   Even more problematic is the claim that chemical fertilizers:

   “promoted substantial plant uptake of soil available phosphorus”
   
   

Author Response

The abstract clearly states the research problem, experimental options, main results and practical conclusion. However, the abstract is currently too descriptive and in places draws conclusions that are not fully supported by the presented results. The transition from the established correlational or regional differences to causal statements about the factors determining productivity is particularly problematic. The first sentence is very long and loaded with information. In addition, the wording “regional environmental differences” is quite broad, although later it mainly refers to soil properties.From a scientific point of view, the objective should accurately reflect what was actually studied: the effect of fertilization on aboveground biomass and soil nutrient indicators and the differences in these indicators between regions.The biggest shortcoming of the methodological part of the abstract is that there is almost no information about the experimental design of the study.
Revised as follows:
Abstract: This study evaluated the effects of chemical and organic fertilization on aboveground biomass and soil properties across three natural grassland regions in the middle section of the Greater Khingan Mountains. Field experiments were conducted in Keyouqian Banner, Keyouzhong Banner, and Zhalaite Banner using three treatments: fencing enclosure (control), fencing enclosure + chemical fertilizer, and fencing enclosure + organic fertilizer, each with three biological replicates. Both chemical and organic fertilization significantly increased aboveground biomass by 30.41% and 24.56%, respectively (P < 0.05), with no significant difference between treatments. Chemical fertilization significantly reduced soil available phosphorus by 9.01% (P < 0.05), whereas organic fertilization had no significant effect on the measured soil properties (P > 0.05). Aboveground biomass and soil properties differed among the three regions, and these differences were associated with variations in soil pH and background soil conditions. These findings indicate that fertilization effectively enhanced grassland productivity, whereas biomass and soil responses varied among regions with different soil conditions, highlighting the importance of considering regional soil characteristics when interpreting fertilization responses and developing grassland management strategies.

 

 

The introduction should more clearly justify the relevance and scientific issues of the topic under consideration. At present, it is not sufficiently clear what specific scientific problem is being solved, what relevance this problem has for the natural grasslands of the Greater Khingan Mountains region, and what research gap it aims to fill. The research objective is also not clearly formulated. It is recommended to consistently move from the general context of the problem to the specific scientific gap, justify the necessity of studying fertilization and regional soil conditions, and clearly and unambiguously formulate the research objective. The objective should directly reflect the factors studied, the indicators evaluated, and their interrelationships. In addition, it would be appropriate to clearly identify the research hypotheses or research questions to make it easier to assess whether the selected methods and the presented results allow answering the raised problem.
Revisions to the second and third paragraphs of the Introduction:
Among the measures for restoring degraded grasslands, fertilization can rapidly replenish soil nutrients, promote vegetation growth, and effectively enhance vegetation coverage and biomass; it is therefore a widely applied and highly effective restoration approach [8-10]. At present, the management of degraded grasslands in China relies predominantly on inorganic chemical fertilizers [11]. Although these fertilizers can improve soil fertility in the short term, they are characterized by a short duration of efficacy and a propensity to cause non-point source environmental pollution [12]. In contrast, organic fertilizers offer a more balanced nutrient composition; after microbial decomposition they generate various bioactive substances that support normal plant growth and development [13]. Previous studies have confirmed that organic fertilizer application can increase grassland aboveground biomass and raise the proportion of gramineous forage species [14]. Moreover, organic fertilizers can ameliorate soil physicochemical properties, thereby influencing vegetation biomass accumulation [15]; the biological and biochemical characteristics of soils receiving organic fertilizer also respond more sensitively to environmental changes and fertilization management practices [16]. To date, existing research has not yet systematically compared the restoration efficacy of organic versus chemical fertilizers on degraded grasslands, nor has it thoroughly investigated whether the restoration effects of a given fertilizer type vary regionally across different degraded grassland types. It is widely assumed that chemical fertilizers produce rapid but short-lived effects, whereas organic fertilizers exert more stable but slower-acting effects. However, whether this assumption holds for all degraded grassland types remains uncertain, and it still lacks sufficient experimental validation.

This study selected three different types of natural grasslands in Keyouqian Banner, Keyouzhong Banner, and Zhalaite Banner as research objects. Three experimental treatments were established in each region: fencing enclosure + chemical fertilizer application, fencing enclosure + organic fertilizer application, and fencing enclosure alone. The effects of these measures on grassland aboveground biomass and soil nutrient indicators (soil organic matter, nitrogen, phosphorus, potassium, and pH) were systematically investigated. On this basis, correlation analysis was employed to reveal the intrinsic coupling relationships between soil nutrient characteristics and aboveground biomass, while correspondence analysis was used to elucidate the comprehensive response patterns of various indicators to different restoration measures. The findings are expected to further enrich the understanding of the response mechanisms of grassland–soil systems under different restoration regimes and to provide a scientific basis for regionally tailored and precise grassland management and ecological restoration practices.

2. Experimental design.

Three variants are specified – control, chemical fertilizers and organic fertilizers – and three biological replicates. However, the wording “fencing enclosure (control)” raises doubts about the control variant. All variants, as understood from the description, were fenced, therefore it should be clearly explained whether the control was only a fenced area without fertilization, or whether there was also an unfenced control. This is important, because fencing itself can affect vegetation biomass.

It is also unclear how the experimental plots were arranged: whether their locations were selected randomly, or whether a block experimental design was used. A plot layout diagram should be provided or at least the randomization principle should be described. The methodology section needs to be significantly supplemented and refined, primarily in terms of experimental design, fertilization time and rates, statistical model, biological replicates, and sample preparation. At present, it is not sufficiently clear what the actual experimental unit is and whether the chosen statistical analysis corresponds to the study structure. It is particularly important to resolve the issue of possible pseudoreplication and justify the use of one-way ANOVA when the study compares three regions, three fertilization options, and two-year data. Without these refinements, the statistical validity of the results and the repeatability of the study are not sufficiently assured.

 

2.2. Experimental design

Three experimental sites were selected in the middle section of the Greater Khingan Mountains (Keyouqian Banner, Keyouzhong Banner, and Zhalaite Banner). At each site, three treatments were established: fencing enclosure (control, CK), fencing enclosure + chemical fertilizer (CF), and fencing enclosure + organic fertilizer (OF). Each treatment had three biological replicates, with each replicate consisting of one experimental plot of 25 m². Organic fertilizer was applied at 2000 kg hm⁻² (N+P₂O₅+K₂O ≥ 8.5%；Organic matter ≥ 45%；Humic acid ≥ 20%；Amino acid ≥ 10%；Beneficial microorganisms ≥ 2.0 × 10⁸ CFU g⁻¹), and chemical fertilizer was applied at 1050 kg hm⁻² (nutrient ratio N:P₂O₅:K₂O = 26:11:11).Fertilization was performed in late May, once per year. The fertilization rate and frequency were based on the conventional fertilization rates and frequencies used for local crops.

（Note: The data from the two years were pooled for analysis. This experiment included three fertilization treatments and three regions, which allowed a two-factor experimental design to be constructed. Due to climatic influences, the data exhibited a certain degree of interannual fluctuation. To make the data relatively stable, we decided to pool the data from the two years. When the data were analyzed separately by year, the considerable climatic differences among years and regions—especially the marked interannual variation in climate—led to substantial discrepancies in the data. The unpooled data exhibited relatively weak central tendency, whereas pooling better reflected the central tendency of the data. The ANOVA performed on the pooled dataset was essentially based on a block design; in other words, this experimental design facilitated redundancy analysis and made it easier to reveal the patterns of fertilization effects.）

 

Results. This section clearly shows that both mineral and organic fertilizers significantly increased aboveground biomass, but no significant difference was found between these two fertilization options. This is an important main result of the study. It is also properly highlighted that mineral fertilizers significantly reduced the amount of available phosphorus, while other assessed soil indicators did not change significantly.

However, the presentation of the results is mainly limited to statements about statistical significance. Actual indicator values, their percentage change, or other quantitative parameters are missing. P values ​​alone do not allow for an assessment of the biological or practical magnitude of the differences found. It is recommended to provide at least the averages of the main results and their changes in the text, especially aboveground biomass and available phosphorus.

Reply as follows:

5. Conclusions

Both chemical and organic fertilizers significantly increased grassland aboveground biomass (P < 0.05), yet their effects on soil nutrient dynamics differed. Chemical fertilizer rapidly alleviated nitrogen limitation, stimulating an increase in aboveground biomass; plants consumed substantial amounts of soil available phosphorus to support biomass accumulation, potentially leading to a decrease in soil available phosphorus content. In contrast, organic fertilizer, through slow nutrient release, maintained grassland productivity while not causing substantial accumulation of soil available nutrients.

Grassland aboveground biomass exhibited significant regional differences (P < 0.05), which largely reflected differences in soil background conditions. In Keyouqian Banner, relatively lower soil pH and higher contents of soil organic matter and available nutrients indicated superior soil conditions and higher grassland productivity. In comparison, Keyouzhong Banner and Zhalaite Banner had stronger soil alkalinity and lower background fertility, and their biomass exhibited a more pronounced response to fertilization. These results indicate that soil background conditions significantly influence fertilization effects and should be taken into account when interpreting the vegetation and soil response characteristics of different grassland regions.

 

It should also be clarified whether the data presented for 2021 and 2022 were combined. Since the study was conducted over two years, the results section should clearly show whether there were significant differences between years and how the year factor was taken into account in the statistical analysis. The main limitation is that the results are insufficient to support the claims made in the abstract and conclusions that soil pH and nutrient status "control" aboveground biomass or that productivity increases in different regions are more dependent on fertilization. This would require additional statistical analysis, especially the assessment of the interaction between region and fertilization.
Reply as follows:

The data from the two years were pooled for analysis. This experiment included three fertilization treatments and three regions, which allowed a two-factor experimental design to be constructed. Due to climatic influences, the data exhibited a certain degree of interannual fluctuation. To make the data relatively stable, we decided to pool the data from the two years. When the data were analyzed separately by year, the considerable climatic differences among years and regions—especially the marked interannual variation in climate—led to substantial discrepancies in the data. The unpooled data exhibited relatively weak central tendency, whereas pooling better reflected the central tendency of the data. The ANOVA performed on the pooled dataset was essentially based on a block design; in other words, this experimental design facilitated redundancy analysis and made it easier to reveal the patterns of fertilization effects.

 

 

The conclusions clearly summarize the main results of the study, but their current formulation is too categorical and in places goes beyond the limits of the study data. Causal claims about the mechanisms of action of fertilizers, the impact of soil properties and recommendations for grassland restoration are particularly problematic.

1. The first conclusion is not fully supported by the studies.

The claim that chemical fertilizers:

“rapidly supplied nitrogen to relieve nutrient limitation”

is not directly proven by the results presented. The study found an increase in aboveground biomass, but it was not shown that the rapid supply of nitrogen was the mechanism for this change.

Even more problematic is the claim that chemical fertilizers:

“promoted substantial plant uptake of soil available phosphorus”
Reply as follows:
Revisions have been made to address the causal statements regarding the mechanisms of fertilizer action, the effects of soil properties, and grassland restoration recommendations. The assertion that fertilization causes changes in soil available phosphorus has been rephrased as an inferential statement. For the grassland restoration recommendations, the causal wording has been revised to state that soil background conditions influence fertilization effects.Details of the revisions can be found in Section “5. Conclusions” above or in the returned manuscript.

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

1. Please provide the background soil properties (baseline soil characteristics) of the experimental site.
2. Please provide a more detailed description of the soil sampling procedures, including the specific sampling protocol and sample processing methods.
3. In the Data Analysis section, the statement that "the data were organized using WPS 2020" is unnecessary, as data organization is a routine step in data processing and does not need to be described.
4. In Figures 1 and 2, for treatments showing no significant differences, the notation "ns" is sufficient. There is no need to additionally label them with the letter "A".
5. Throughout the manuscript, the sampling data from 2021 and 2022 are presented as combined results, without separately showing interannual differences. Moreover, it is unclear whether a two-way ANOVA was conducted to verify that the "year" factor and its interaction effects were not significant before pooling the data. It is recommended that the statistical results for interannual differences be provided.
6. The manuscript directly interprets the significant correlations shown in the correlation heatmap as causal driving relationships. However, Pearson correlation analysis only reflects covariation and cannot be used to infer causal mechanisms. It is recommended that the wording be revised to indicate that "significant correlations were observed." Further analyses, such as RDA or PLS-PM, could be used to clarify the direct effects of soil nutrients on biomass.
7. The correspondence analysis presented in Section 3.5 provides only a qualitative description of the spatial distribution patterns. The manuscript does not report the proportion of variance explained by each ordination axis or the statistical significance of differences among treatment groups. It is recommended to provide the variance explained by the ordination axes as well as the results of ANOSIM to quantitatively evaluate the degree of community–nutrient differentiation among different fertilization treatments.
8. The manuscript proposes that "chemical fertilization promotes greater plant uptake of available phosphorus, thereby reducing soil available phosphorus content" as the primary mechanism. However, this study did not measure plant total phosphorus uptake, soil phosphatase activity, or phosphorus fractionation, and therefore lacks direct evidence to support this conclusion. It is recommended to cite and compare relevant studies with similar findings to strengthen the discussion.
9. A two-year observation period is insufficient to capture the long-term cumulative effects of fertilization on grassland ecosystems. In addition, changes in species diversity were not monitored. It is recommended that the limitations of the present study be explicitly discussed at the end of the Discussion section, together with suggestions for future long-term monitoring and research.

Author Response

Thank you very much for your suggestions and corrections on my article. Below are the revisions I have made.

1. Please provide the background soil properties (baseline soil characteristics) of the experimental site.
   Revisions have been made to Section “1. Study area”, and brief supplementary information on the background soil properties of the experimental sites has been added at the end of each paragraph.
   Revised as follows:
   2.1. Study area
   The experimental site in Keyouqian Banner (HRQ) is located in Manzutun Manchu Township, Keyouqian Banner, Hinggan League, Inner Mongolia Autonomous Region (120°58′25.46″ E, 46°27′2.17″ N), at an elevation of 719 m. The region has a temperate continental monsoon climate, with a mean annual temperature of 4 °C, a frost-free period of approximately 100 d, and mean annual precipitation of 410–440 mm. The soil type is chernozem(Exhibiting relatively high organic matter content and favorable soil structure).
   The experimental site in Keyouzhong Banner (HRZ) is situated in Daiqintala Sumu, Keyouzhong Banner, Hinggan League, Inner Mongolia Autonomous Region (121°32′16.19″ E, 45°08′9.39″ N), at an elevation of 273 m. It also experiences a temperate continental monsoon climate, with a mean annual temperature of 4.8 °C, a frost-free period of approximately 120 d, and mean annual precipitation of 370–380 mm. The soil type is saline-alkali soil(Soils characterized by salt accumulation and sodium ion enrichment, with a relatively high pH).
   The experimental site in Zhalaite Banner (ZHQ) is located in Tumuji Town, Zhalaite Banner, Hinggan League, Inner Mongolia Autonomous Region (122°58′45.10″ E, 46°9′49.26″ N), at an elevation of 163 m. The climate is temperate continental monsoon, with a mean annual temperature of 4.3 °C, a frost-free period of approximately 130 d, and mean annual precipitation of 350–400 mm. The soil type is chestnut soil(Characterized by a certain level of organic matter and carbonates).
2. Please provide a more detailed description of the soil sampling procedures, including the specific sampling protocol and sample processing methods.
   Supplementary information has been added in Section “2.3. Measurement indicators and methods”.
   Revised as follows:
   3. Measurement indicators and methods
   Field sampling was conducted in August 2021 and August 2022, with new quadrats randomly established each year. Within each experimental plot, three standard 1 m × 1 m quadrats were randomly established. Following vegetation community surveys, soil samples from the 0–20 cm layer were collected from each quadrat, and vegetation and soil indicators were measured concurrently using the following methods: Aboveground biomass: samples were brought back to the laboratory, dried at 105 °C for 30 min to deactivate enzymes, and then further dried at 65 °C for 24 h until constant weight; Soil pH: measured with a pH meter at a soil-to-water ratio of 1:5 using distilled water; Soil organic matter: determined by the potassium dichromate (K₂Cr₂O₇) volumetric method with oil-bath heating; Soil alkali-hydrolyzable nitrogen: measured by the diffusion absorption method; Soil available phosphorus: determined by the molybdenum–antimony anticolorimetric method; Soil available potassium: extracted with ammonium acetate and measured by flame photometry. Soil samples collected from the three quadrats were analyzed separately.
3. In the Data Analysis section, the statement that "the data were organized using WPS 2020" is unnecessary, as data organization is a routine step in data processing and does not need to be described.
   Revisions have been made in Section “2.4. Data analysis”.
   Revised as follows:
   4. Data analysis
   One-way analysis of variance (ANOVA) was performed among treatments using SPSS 20.0. Pearson correlation analyses were conducted separately for different treatments and different plots. Correspondence analysis (CA) was employed across different regions to visualize the multivariate associations among treatments, aboveground biomass, and soil properties. Correlation heatmaps and correspondence analysis plots were generated using Origin 2024 Pro and R 3.3.1 to systematically examine the differences and intrinsic relationships among vegetation characteristics, soil nutrients, and grassland aboveground biomass under different experimental treatments.
4. In Figures 1 and 2, for treatments showing no significant differences, the notation "ns" is sufficient. There is no need to additionally label them with the letter "A".
   The drawing has been remade and revised.However, I cannot upload files in this chat box. I have uploaded the file, and you can view it in the file.
   
   
5. Throughout the manuscript, the sampling data from 2021 and 2022 are presented as combined results, without separately showing interannual differences. Moreover, it is unclear whether a two-way ANOVA was conducted to verify that the "year" factor and its interaction effects were not significant before pooling the data. It is recommended that the statistical results for interannual differences be provided.
   Revised as follows:
   The data from the two years were pooled for analysis. This experiment included three fertilization treatments and three regions, which allowed a two-factor experimental design to be constructed. Due to climatic influences, the data exhibited a certain degree of interannual fluctuation. To make the data relatively stable, we decided to pool the data from the two years. When the data were analyzed separately by year, the considerable climatic differences among years and regions—especially the marked interannual variation in climate—led to substantial discrepancies in the data. The unpooled data exhibited relatively weak central tendency, whereas pooling better reflected the central tendency of the data. The ANOVA performed on the pooled dataset was essentially based on a block design; in other words, this experimental design facilitated redundancy analysis and made it easier to reveal the patterns of fertilization effects.
6. The manuscript directly interprets the significant correlations shown in the correlation heatmap as causal driving relationships. However, Pearson correlation analysis only reflects covariation and cannot be used to infer causal mechanisms. It is recommended that the wording be revised to indicate that "significant correlations were observed." Further analyses, such as RDA or PLS-PM, could be used to clarify the direct effects of soil nutrients on biomass.
   The expression has been revised. Revisions are as follows:
   Discussion section:
   Soil organic matter releases organic acids and carbon dioxide during decomposition, thereby lowering soil pH and alleviating soil alkalization. A slightly acidic to neutral soil environment can effectively activate fixed phosphorus, reduce the adsorption and fixation of potassium by clay minerals, and substantially enhance soil phosphorus and potassium availability [29]. In addition, soil alkali-hydrolyzable nitrogen is mainly derived from the mineralization of organic matter; a higher organic matter content can maintain a sustained nitrogen supply potential and is compatible with a lower soil pH environment [30,31]. Appropriate pH conditions can activate soil microbial activity [32], accelerate organic matter decomposition and nutrient mineralization, and promote the transformation of organic nitrogen into plant-available alkali-hydrolyzable nitrogen, thereby increasing the alkali-hydrolyzable nitrogen content and further enhancing the level of soil available nutrients [33]. Conversely, high-pH, strongly alkaline soils can significantly inhibit microbial activity and nutrient mineralization processes, reduce soil potassium and phosphorus availability, and constrain the soil nutrient supply capacity [30,34]. The differences in soil physicochemical indicators among the three regions in this study were highly consistent with the above patterns. As shown in Figure 1, different treatments did not significantly change soil pH (P > 0.05). As shown in Figure 2, soil pH in Keyouqian Banner was significantly lower than that in Keyouzhong Banner (P < 0.05), and soil pH in Keyouzhong Banner was significantly lower than that in Zhalaite Banner (P < 0.05). As shown in Figure 2, aboveground biomass in Keyouqian Banner and Keyouzhong Banner was significantly higher than that in Zhalaite Banner (P < 0.05). Meanwhile, the negative correlation between aboveground biomass and alkali-hydrolyzable nitrogen in Keyouqian Banner (Figure 4) may be attributable to the stronger uptake of soil alkali-hydrolyzable nitrogen by the higher biomass in this region, thereby reducing the residual alkali-hydrolyzable nitrogen content in the soil.In summary, fertilization treatments did not alter soil pH; slightly acidic, low-pH soil environments are more conducive to nutrient activation and accumulation [35], whereas alkaline, high-pH environments impede nutrient transformation and reduce soil fertility [36].
   
   
7. The correspondence analysis presented in Section 3.5 provides only a qualitative description of the spatial distribution patterns. The manuscript does not report the proportion of variance explained by each ordination axis or the statistical significance of differences among treatment groups. It is recommended to provide the variance explained by the ordination axes as well as the results of ANOSIM to quantitatively evaluate the degree of community–nutrient differentiation among different fertilization treatments.
   The drawing has been remade and revised.However, I cannot upload files in this chat box. I have uploaded the file, and you can view it in the file.
   The corresponding analysis plot has been remade, with the proportion of explained variance for each ordination axis added, and all P < 0.05.
    
8. The manuscript proposes that "chemical fertilization promotes greater plant uptake of available phosphorus, thereby reducing soil available phosphorus content" as the primary mechanism. However, this study did not measure plant total phosphorus uptake, soil phosphatase activity, or phosphorus fractionation, and therefore lacks direct evidence to support this conclusion. It is recommended to cite and compare relevant studies with similar findings to strengthen the discussion.
   In response to the above issues, I have revised this causal assertion to a speculative conclusion, which is more consistent with the reality of this paper. The revised version is as follows:
   This study found that chemical fertilizer application significantly reduced soil available phosphorus content (P < 0.05), a phenomenon consistent with the observations of Yang et al. [24], who reported that chemical fertilizer inputs can simultaneously increase vegetation biomass and decrease soil available phosphorus. The underlying mechanism is that nitrogen is one of the primary limiting factors for plant growth [25]. Chemical fertilizers rapidly supply high concentrations of inorganic nitrogen to the soil, effectively alleviating nitrogen limitation and promoting rapid plant growth. During this process, the rate of phosphorus uptake and utilization by plants increases substantially, while soil phosphorus fixation is intensified, ultimately leading to a decline in soil available phosphorus content [26,27]. Combined with the correlation analysis under the chemical fertilizer treatment in this study (Figure 3a), aboveground biomass was significantly positively correlated with soil available phosphorus (P < 0.05). It is therefore speculated that the nutrient limiting factor in the grassland system may also have shifted after chemical fertilizer input in this study. Once nitrogen becomes sufficient, phosphorus may become the new growth-limiting factor; plants consume large amounts of soil available phosphorus to support biomass accumulation, resulting in decreased soil available phosphorus content and significantly increased aboveground biomass.
9. A two-year observation period is insufficient to capture the long-term cumulative effects of fertilization on grassland ecosystems. In addition, changes in species diversity were not monitored. It is recommended that the limitations of the present study be explicitly discussed at the end of the Discussion section, together with suggestions for future long-term monitoring and research.
   Relevant content has been added at the end of the conclusion. Revisions are as follows:
   In addition, although soil properties were strongly associated with differences in aboveground biomass among regions, the three study regions differed not only in soil properties but also in elevation, precipitation, soil type, and other environmental conditions. This study was unable to fully disentangle the independent contributions of soil factors and other environmental factors to vegetation productivity. Future studies should incorporate variables such as climate, topography, and long-term changes to further clarify the relative roles of different environmental factors in driving changes in grassland productivity.

Author Response File: Author Response.pdf

Reviewer 4 Report

Comments and Suggestions for Authors

The manuscript investigates the effects of chemical and organic fertilizer application on aboveground biomass and soil nutrient characteristics at three grassland sites in Inner Mongolia. The topic is relevant, and the regional comparison has practical value for grassland restoration. However, I think that several methodological and statistical issues should be addressed. You can find my comments about the paper below:

1-Lines 12–18. The aim in the abstract should explicitly state that the control treatment consisted of fencing without fertilizer. At present, "control" is less informative than the description given later in the methods.

2-Lines 24–25. Please avoid causal language such as "primarily governed by soil pH" unless this relationship was experimentally demonstrated.

3-Lines 35. Please use different words in keywords from the title of the paper. "Different regions" is very general.

4-Lines 41–49. The statement that China's grassland area ranks first in the world should be supported by a directly relevant reference.

5-Lines 56–60. Please check reference [13]. The cited reference appears to concern combined nitrogen, phosphorus, and potassium fertilization rather than organic fertilizer. The citation may not support the statement concerning organic fertilizer decomposition and bioactive substances.

6-Lines 64–69. The statement that previous research has not systematically compared chemical and organic fertilizer appears too broad. Please qualify this research gap geographically or ecologically and support it with appropriate literature.

7-Lines 88–104. The study area description is clear, but more information about vegetation composition and initial grassland condition would improve ecological interpretation. 

8-Lines 105–112. Explain how the fertilizer rates were selected and provide references supporting these application rates.

9-Lines 105–112. Please report the nutrient composition of the organic fertilizer, not only organic matter ≥30%.

10-Lines 105–112. Explain the experimental plot arrangement and randomization procedure.

11-Lines 113–114. Specify the exact sampling dates or at least months for 2021 and 2022.

12-Lines 113–125. Clarify whether the same quadrats were sampled repeatedly or new quadrats were randomly established each year.

13-Lines 117–118. The authors state that plants were clipped and "weighed to determine aboveground biomass." Please indicate whether biomass was measured as fresh weight or dry weight.

14-Lines 119–125. Standard analytical method references should be provided for the soil measurements.

15-Lines 126–132. The software information is less important than the statistical model. Please provide the actual analytical procedures, assumptions, factors, interactions, post-hoc tests, and significance level. In addition to the experimental design contains at least two main factors: treatment and site. It also appears to contain a third factor year. However, the authors report only one-way ANOVA. A factorial model would be more appropriate.

16-Lines 136–145. Please provide exact test statistics, degrees of freedom, and P-values where possible rather than reporting only P < 0.05.

17-Figure 1. The figure apparently pools observations among sites and possibly years. Please clarify exactly which observations are represented by each bar.

18-Figure 1. Please specify the sample size represented by each mean and error bar.

19-Lines 152–166. The same concern applies to the comparison among regions/sites. The analysis apparently pools different fertilizer treatments. Treatment effects could influence the regional means.

20-Lines 175–193. Please report correlation coefficients in the text where they are biologically important, rather than describing only whether correlations were statistically significant.

21-Figures 3 and 4. Adding the numerical correlation coefficients to the heatmaps would improve interpretation.

22-Lines 232–246. Please check the repeated reference to available phosphorus described above.

23-Figure 5. The figure would be easier to interpret if axis percentages were shown and labels were enlarged.

24-Lines 274–286. This paragraph contains considerable repetition. The effect of chemical fertilizer is stated, followed by the effect of organic fertilizer, followed again by the statement that both treatments increased biomass. The paragraph can be shortened considerably.

25-Lines 277–281. There are punctuation and spacing problems around the references, for example "[19].The" and "[22].The". Please proofread the manuscript carefully.

26-Lines 318–327. Please replace "regional" with "site-level" where appropriate unless the authors can justify regional-level replication.

27-Lines 328–342. This section includes several broad statements concerning soil pH and nutrient cycling. The authors should ensure that each statement is supported by an appropriate reference.

28-Lines 368–386. The Conclusions section should focus more directly on results demonstrated by the experiment and reduce mechanistic interpretations that were not directly measured.

29-Lines 376–386. Recommendations for natural recovery versus fertilization are interesting, but I think that the two-year experiment may not be sufficient to support long-term restoration recommendations. Please acknowledge this limitation.

30-Line 388. The heading "6. Patents" is empty and should be removed if there are no patents associated with the study.

31- Please standardize the use of "aboveground biomass" versus "above-ground biomass."

32- Please standardize P-value formatting. Both P < 0.05 and forms using a different less-than symbol appear in the manuscript.

Author Response

Thank you for your suggestions and corrections. Below is the revised version of my article.

The manuscript investigates the effects of chemical and organic fertilizer application on aboveground biomass and soil nutrient characteristics at three grassland sites in Inner Mongolia. The topic is relevant, and the regional comparison has practical value for grassland restoration. However, I think that several methodological and statistical issues should be addressed. You can find my comments about the paper below:

1. 1-Lines 12– The aim in the abstract should explicitly state that the control treatment consisted of fencing without fertilizer. At present, "control" is less informative than the description given later in the methods.
   Based on the above comments, both the abstract and experimental design have been revised. The revisions are as follows:
   Abstract: This study evaluated the effects of chemical and organic fertilization on aboveground biomass and soil properties across three natural grassland regions in the middle section of the Greater Khingan Mountains. Field experiments were conducted in Keyouqian Banner, Keyouzhong Banner, and Zhalaite Banner using three treatments: fencing enclosure (control), fencing enclosure + chemical fertilizer, and fencing enclosure + organic fertilizer, each with three biological replicates. Both chemical and organic fertilization significantly increased aboveground biomass by 30.41% and 24.56%, respectively (P < 0.05), with no significant difference between treatments. Chemical fertilization significantly reduced soil available phosphorus by 9.01% (P < 0.05), whereas organic fertilization had no significant effect on the measured soil properties (P > 0.05). Aboveground biomass and soil properties differed among the three regions, and these differences were associated with variations in soil pH and background soil conditions. These findings indicate that fertilization effectively enhanced grassland productivity, whereas biomass and soil responses varied among regions with different soil conditions, highlighting the importance of considering regional soil characteristics when interpreting fertilization responses and developing grassland management strategies.
   2.2. Experimental design
   Three experimental sites were selected in the middle section of the Greater Khingan Mountains (Keyouqian Banner, Keyouzhong Banner, and Zhalaite Banner). At each site, three treatments were established: fencing enclosure (control, CK), fencing enclosure + chemical fertilizer (CF), and fencing enclosure + organic fertilizer (OF). Each treatment had three biological replicates, with each replicate consisting of one experimental plot of 25 m². Organic fertilizer was applied at 2000 kg hm⁻² (N+P₂O₅+K₂O ≥ 8.5%；Organic matter ≥ 45%；Humic acid ≥ 20%；Amino acid ≥ 10%；Beneficial microorganisms ≥ 2.0 × 10⁸ CFU g⁻¹), and chemical fertilizer was applied at 1050 kg hm⁻² (nutrient ratio N:P₂O₅:K₂O = 26:11:11).Fertilization was performed in late May, once per year. The fertilization rate and frequency were based on the conventional fertilization rates and frequencies used for local crops.
2. 2-Lines 24– Please avoid causal language such as "primarily governed by soil pH" unless this relationship was experimentally demonstrated.
   Since the methods adopted in this study are correlation analysis and correspondence analysis, which respectively represent the covariation and association between indicators, causal statements are inappropriate. Therefore, based on the content of this study and findings from other research, this paper converts such causal descriptions into speculative ones. The revised parts include the abstract, discussion and conclusion. The revised results are as follows:
   Abstract: This study evaluated the effects of chemical and organic fertilization on aboveground biomass and soil properties across three natural grassland regions in the middle section of the Greater Khingan Mountains. Field experiments were conducted in Keyouqian Banner, Keyouzhong Banner, and Zhalaite Banner using three treatments: fencing enclosure (control), fencing enclosure + chemical fertilizer, and fencing enclosure + organic fertilizer, each with three biological replicates. Both chemical and organic fertilization significantly increased aboveground biomass by 30.41% and 24.56%, respectively (P < 0.05), with no significant difference between treatments. Chemical fertilization significantly reduced soil available phosphorus by 9.01% (P < 0.05), whereas organic fertilization had no significant effect on the measured soil properties (P > 0.05). Aboveground biomass and soil properties differed among the three regions, and these differences were associated with variations in soil pH and background soil conditions. These findings indicate that fertilization effectively enhanced grassland productivity, whereas biomass and soil responses varied among regions with different soil conditions, highlighting the importance of considering regional soil characteristics when interpreting fertilization responses and developing grassland management strategies.
   4.1. Effects of different fertilization treatments on grassland aboveground biomass and soil nutrients (The second paragraph)
   This study found that chemical fertilizer application significantly reduced soil available phosphorus content (P < 0.05), a phenomenon consistent with the observations of Yang et al. [24], who reported that chemical fertilizer inputs can simultaneously increase vegetation biomass and decrease soil available phosphorus. The underlying mechanism is that nitrogen is one of the primary limiting factors for plant growth [25]. Chemical fertilizers rapidly supply high concentrations of inorganic nitrogen to the soil, effectively alleviating nitrogen limitation and promoting rapid plant growth. During this process, the rate of phosphorus uptake and utilization by plants increases substantially, while soil phosphorus fixation is intensified, ultimately leading to a decline in soil available phosphorus content [26,27]. Combined with the correlation analysis under the chemical fertilizer treatment in this study (Figure 3a), aboveground biomass was significantly positively correlated with soil available phosphorus (P < 0.05). It is therefore speculated that the nutrient limiting factor in the grassland system may also have shifted after chemical fertilizer input in this study. Once nitrogen becomes sufficient, phosphorus may become the new growth-limiting factor; plants consume large amounts of soil available phosphorus to support biomass accumulation, resulting in decreased soil available phosphorus content and significantly increased aboveground biomass.
   4.2. Effects of different regions on grassland aboveground biomass and soil nutrients (The second paragraph)
   Soil organic matter releases organic acids and carbon dioxide during decomposition, thereby lowering soil pH and alleviating soil alkalization. A slightly acidic to neutral soil environment can effectively activate fixed phosphorus, reduce the adsorption and fixation of potassium by clay minerals, and substantially enhance soil phosphorus and potassium availability [29]. In addition, soil alkali-hydrolyzable nitrogen is mainly derived from the mineralization of organic matter; a higher organic matter content can maintain a sustained nitrogen supply potential and is compatible with a lower soil pH environment [30,31]. Appropriate pH conditions can activate soil microbial activity [32], accelerate organic matter decomposition and nutrient mineralization, and promote the transformation of organic nitrogen into plant-available alkali-hydrolyzable nitrogen, thereby increasing the alkali-hydrolyzable nitrogen content and further enhancing the level of soil available nutrients [33]. Conversely, high-pH, strongly alkaline soils can significantly inhibit microbial activity and nutrient mineralization processes, reduce soil potassium and phosphorus availability, and constrain the soil nutrient supply capacity [30,34]. The differences in soil physicochemical indicators among the three regions in this study were highly consistent with the above patterns. As shown in Figure 1, different treatments did not significantly change soil pH (P > 0.05). As shown in Figure 2, soil pH in Keyouqian Banner was significantly lower than that in Keyouzhong Banner (P < 0.05), and soil pH in Keyouzhong Banner was significantly lower than that in Zhalaite Banner (P < 0.05). As shown in Figure 2, aboveground biomass in Keyouqian Banner and Keyouzhong Banner was significantly higher than that in Zhalaite Banner (P < 0.05). Meanwhile, the negative correlation between aboveground biomass and alkali-hydrolyzable nitrogen in Keyouqian Banner (Figure 4) may be attributable to the stronger uptake of soil alkali-hydrolyzable nitrogen by the higher biomass in this region, thereby reducing the residual alkali-hydrolyzable nitrogen content in the soil.In summary, fertilization treatments did not alter soil pH; slightly acidic, low-pH soil environments are more conducive to nutrient activation and accumulation [35], whereas alkaline, high-pH environments impede nutrient transformation and reduce soil fertility [36].
   5. Conclusions
   Both chemical and organic fertilizers significantly increased grassland aboveground biomass (P < 0.05), yet their effects on soil nutrient dynamics differed. Chemical fertilizer rapidly alleviated nitrogen limitation, stimulating an increase in aboveground biomass; plants consumed substantial amounts of soil available phosphorus to support biomass accumulation, potentially leading to a decrease in soil available phosphorus content. In contrast, organic fertilizer, through slow nutrient release, maintained grassland productivity while not causing substantial accumulation of soil available nutrients.
   Grassland aboveground biomass exhibited significant regional differences (P < 0.05), which largely reflected differences in soil background conditions. In Keyouqian Banner, relatively lower soil pH and higher contents of soil organic matter and available nutrients indicated superior soil conditions and higher grassland productivity. In comparison, Keyouzhong Banner and Zhalaite Banner had stronger soil alkalinity and lower background fertility, and their biomass exhibited a more pronounced response to fertilization. These results indicate that soil background conditions significantly influence fertilization effects and should be taken into account when interpreting the vegetation and soil response characteristics of different grassland regions.
3. 3-Lines 35. Please use different words in keywords from the title of the paper. "Different regions" is very general.
   Revised as follows:
   Replace different regions with different soil conditions.
4. 4-Lines 41– The statement that China's grassland area ranks first in the world should be supported by a directly relevant reference.
   The following literature has been inserted to substantiate the statement that "China ranks first in the world in terms of grassland area".
   3. Hou M, Ge J, Xiu Y, et al. The urgent need to develop a new grassland map in China: based on the consistency and accuracy of ten land cover products[J]. Science China Life Sciences, 2023, 66(2): 385-405.
5. 5-Lines 56– Please check reference [13]. The cited reference appears to concern combined nitrogen, phosphorus, and potassium fertilization rather than organic fertilizer. The citation may not support the statement concerning organic fertilizer decomposition and bioactive substances.
   References have been revised.
   Yuvasri E A, Anandham R, Balachandar D, et al. Harnessing the power of traditional organic formulations for crop growth and microbial harmony[J]. Frontiers in Bioscience-Elite, 2024, 16(2): 14.
6. 6-Lines 64– The statement that previous research has not systematically compared chemical and organic fertilizer appears too broad. Please qualify this research gap geographically or ecologically and support it with appropriate literature.
   Revised as follows:
   To date, existing research has not yet systematically compared the restoration efficacy of organic versus chemical fertilizers on degraded grasslands, nor has it thoroughly investigated whether the restoration effects of a given fertilizer type vary regionally across different degraded grassland types. It is widely assumed that chemical fertilizers produce rapid but short-lived effects, whereas organic fertilizers exert more stable but slower-acting effects. However, whether this assumption holds for all degraded grassland types remains uncertain, and it still lacks sufficient experimental validation.
7. 7-Lines 88– The study area description is clear, but more information about vegetation composition and initial grassland condition would improve ecological interpretation. 
   The present study focused on different treatments and soil conditions; therefore, we only concentrated on aboveground biomass and soil properties, and did not place emphasis on vegetation composition and initial grassland status. Nevertheless, we supplemented an overview of each study area, including the general soil type of each site. Revised as follows:
   The experimental site in Keyouqian Banner (HRQ) is located in Manzutun Manchu Township, Keyouqian Banner, Hinggan League, Inner Mongolia Autonomous Region (120°58′25.46″ E, 46°27′2.17″ N), at an elevation of 719 m. The region has a temperate continental monsoon climate, with a mean annual temperature of 4 °C, a frost-free period of approximately 100 d, and mean annual precipitation of 410–440 mm. The soil type is chernozem(Exhibiting relatively high organic matter content and favorable soil structure).
   The experimental site in Keyouzhong Banner (HRZ) is situated in Daiqintala Sumu, Keyouzhong Banner, Hinggan League, Inner Mongolia Autonomous Region (121°32′16.19″ E, 45°08′9.39″ N), at an elevation of 273 m. It also experiences a temperate continental monsoon climate, with a mean annual temperature of 4.8 °C, a frost-free period of approximately 120 d, and mean annual precipitation of 370–380 mm. The soil type is saline-alkali soil(Soils characterized by salt accumulation and sodium ion enrichment, with a relatively high pH).
   The experimental site in Zhalaite Banner (ZHQ) is located in Tumuji Town, Zhalaite Banner, Hinggan League, Inner Mongolia Autonomous Region (122°58′45.10″ E, 46°9′49.26″ N), at an elevation of 163 m. The climate is temperate continental monsoon, with a mean annual temperature of 4.3 °C, a frost-free period of approximately 130 d, and mean annual precipitation of 350–400 mm. The soil type is chestnut soil(Characterized by a certain level of organic matter and carbonates).
8. 8-Lines 105– Explain how the fertilizer rates were selected and provide references supporting these application rates.

9-Lines 105–112. Please report the nutrient composition of the organic fertilizer, not only organic matter ≥30%.
The above two points respond together:
2.2. Experimental design

Three experimental sites were selected in the middle section of the Greater Khingan Mountains (Keyouqian Banner, Keyouzhong Banner, and Zhalaite Banner). At each site, three treatments were established: fencing enclosure (control, CK), fencing enclosure + chemical fertilizer (CF), and fencing enclosure + organic fertilizer (OF). Each treatment had three biological replicates, with each replicate consisting of one experimental plot of 25 m². Organic fertilizer was applied at 2000 kg hm⁻² (N+P₂O₅+K₂O ≥ 8.5%；Organic matter ≥ 45%；Humic acid ≥ 20%；Amino acid ≥ 10%；Beneficial microorganisms ≥ 2.0 × 10⁸ CFU g⁻¹), and chemical fertilizer was applied at 1050 kg hm⁻² (nutrient ratio N:P₂O₅:K₂O = 26:11:11).Fertilization was performed in late May, once per year. The fertilization rate and frequency were based on the conventional fertilization rates and frequencies used for local crops.

9. 10-Lines 105– Explain the experimental plot arrangement and randomization procedure.
10. 11-Lines 113– Specify the exact sampling dates or at least months for 2021 and 2022.
11. 12-Lines 113– Clarify whether the same quadrats were sampled repeatedly or new quadrats were randomly established each year.
12. 13-Lines 117–The authors state that plants were clipped and "weighed to determine aboveground biomass." Please indicate whether biomass was measured as fresh weight or dry weight.

14-Lines 119–125. Standard analytical method references should be provided for the soil measurements.
Answer the above five questions together. Revisions are as follows:
2.3. Measurement indicators and methods
Field sampling was conducted in August 2021 and August 2022, with new quadrats randomly established each year. Within each experimental plot, three standard 1 m × 1 m quadrats were randomly established. Following vegetation community surveys, soil samples from the 0–20 cm layer were collected from each quadrat, and vegetation and soil indicators were measured concurrently using the following methods: Aboveground biomass: samples were brought back to the laboratory, dried at 105 °C for 30 min to deactivate enzymes, and then further dried at 65 °C for 24 h until constant weight; Soil pH: measured with a pH meter at a soil-to-water ratio of 1:5 using distilled water; Soil organic matter: determined by the potassium dichromate (K₂Cr₂O₇) volumetric method with oil-bath heating; Soil alkali-hydrolyzable nitrogen: measured by the diffusion absorption method; Soil available phosphorus: determined by the molybdenum–antimony anticolorimetric method; Soil available potassium: extracted with ammonium acetate and measured by flame photometry. Soil samples collected from the three quadrats were analyzed separately.

13. 15-Lines 126– The software information is less important than the statistical model. Please provide the actual analytical procedures, assumptions, factors, interactions, post-hoc tests, and significance level. In addition to the experimental design contains at least two main factors: treatment and site. It also appears to contain a third factor year. However, the authors report only one-way ANOVA. A factorial model would be more appropriate.
    Reply as follows:
    The data from the two years were pooled for analysis. This experiment included three fertilization treatments and three regions, which allowed a two-factor experimental design to be constructed. Due to climatic influences, the data exhibited a certain degree of interannual fluctuation. To make the data relatively stable, we decided to pool the data from the two years. When the data were analyzed separately by year, the considerable climatic differences among years and regions—especially the marked interannual variation in climate—led to substantial discrepancies in the data. The unpooled data exhibited relatively weak central tendency, whereas pooling better reflected the central tendency of the data. The ANOVA performed on the pooled dataset was essentially based on a block design; in other words, this experimental design facilitated redundancy analysis and made it easier to reveal the patterns of fertilization effects.
14. 16-Lines 136– Please provide exact test statistics, degrees of freedom, and P-values where possible rather than reporting only P < 0.05.17-Figure 1. The figure apparently pools observations among sites and possibly years. Please clarify exactly which observations are represented by each bar.
    The picture has been reset and revised to make the bar chart and indicators clearer. I cannot upload images in this window, but the reset picture is included in the file I uploaded.
15. 18-Figure 1. Please specify the sample size represented by each mean and error bar.
    Revised as follows:
    Figure 1. Effects of different treatments on grassland aboveground biomass and soil nutrients. Note: Data are presented as mean ± standard error. OF: organic fertilizer; CF: chemical fertilizer; CK: control; AGB: aboveground biomass; SOM: soil organic matter; AN: soil alkali-hydrolyzable nitrogen; AP: soil available phosphorus; AK: soil available potassium; pH: soil pH. Different uppercase letters indicate significant differences among treatments (P < 0.05). n = 6.
    Figure 2. Effects of different regions on grassland aboveground biomass and soil nutrients. Note: Data are presented as mean ± standard error. HRQ: Keyouqian Banner; HRZ: Keyouzhong Banner; ZHQ: Zhalaite Banner; AGB: aboveground biomass; SOM: organic matter; AN: soil alkali-hydrolyzable nitrogen; AP: soil available phosphorus; AK: soil available potassium; pH: soil pH. Different uppercase letters indicate significant differences among regions (P < 0.05).n = 6.
16. 21-Figures 3 and 4. Adding the numerical correlation coefficients to the heatmaps would improve interpretation.
    
    Figures 3 and 4 have been revised.The picture has been reset and revised to make the bar chart and indicators clearer. I cannot upload images in this window, but the reset picture is included in the file I uploaded.
17. 23-Figure 5. The figure would be easier to interpret if axis percentages were shown and labels were enlarged.
    Figure 5 has been revised. The image has been reconfigured and modified to make the bar chart and metrics clearer. I cannot upload images in this window, but the reconfigured image is included in the file I uploaded.
18. 24-Lines 274– This paragraph contains considerable repetition. The effect of chemical fertilizer is stated, followed by the effect of organic fertilizer, followed again by the statement that both treatments increased biomass. The paragraph can be shortened considerably.
    Revise as follows:
    4.1. Effects of different fertilization treatments on grassland aboveground biomass and soil nutrients
    Fertilization is an effective means of enhancing grassland productivity and improving soil nutrient status. Both chemical and organic fertilizers can promote vegetation recovery in grasslands, and although their modes of action differ markedly, their short-term promoting effects are similar. Consistent with the findings of Tong Z et al. [17], Li Fan et al. [18], and E. T. Borer et al. [19], chemical fertilizer can significantly increase grassland aboveground biomass (P < 0.05). Similarly, consistent with the results of Ma K et al. [20], Zhang Chu et al. [21], and Zhang Fengge et al. [22], the application of organic fertilizer can also significantly enhance grassland aboveground biomass (P < 0.05). The conventional perception that chemical fertilizers act quickly while organic fertilizers act slowly is not correct. Based on the results of this study, the effective nutrients ultimately obtained by plants under chemical and organic fertilizer applications may be similar, a view that is also supported by the findings of Lin et al. [23].
19. 25-Lines 277– There are punctuation and spacing problems around the references, for example "[19].The" and "[22].The". Please proofread the manuscript carefully.
    Modified.
20. 26-Lines 318– Please replace "regional" with "site-level" where appropriate unless the authors can justify regional-level replication.
    Modified.
21. 27-Lines 328– This section includes several broad statements concerning soil pH and nutrient cycling. The authors should ensure that each statement is supported by an appropriate reference.
    According to the reviewers' comments, the following reference has been added to this paper to provide proper literature support for the statement "Soil organic matter releases organic acids and carbon dioxide during decomposition, thereby lowering soil pH and alleviating soil alkalization."
    30. Hong S, Piao S, Chen A, et al. Afforestation neutralizes soil pH[J]. Nature communications, 2018, 9(1): 520.
22. 28-Lines 368– The Conclusions section should focus more directly on results demonstrated by the experiment and reduce mechanistic interpretations that were not directly measured.
    Revised as follows:
    5. Conclusions
    Both chemical and organic fertilizers significantly increased grassland aboveground biomass (P < 0.05), yet their effects on soil nutrient dynamics differed. Chemical fertilizer rapidly alleviated nitrogen limitation, stimulating an increase in aboveground biomass; plants consumed substantial amounts of soil available phosphorus to support biomass accumulation, potentially leading to a decrease in soil available phosphorus content. In contrast, organic fertilizer, through slow nutrient release, maintained grassland productivity while not causing substantial accumulation of soil available nutrients.
    Grassland aboveground biomass exhibited significant regional differences (P < 0.05), which largely reflected differences in soil background conditions. In Keyouqian Banner, relatively lower soil pH and higher contents of soil organic matter and available nutrients indicated superior soil conditions and higher grassland productivity. In comparison, Keyouzhong Banner and Zhalaite Banner had stronger soil alkalinity and lower background fertility, and their biomass exhibited a more pronounced response to fertilization. These results indicate that soil background conditions significantly influence fertilization effects and should be taken into account when interpreting the vegetation and soil response characteristics of different grassland regions.
23. 29-Lines 376– Recommendations for natural recovery versus fertilization are interesting, but I think that the two-year experiment may not be sufficient to support long-term restoration recommendations. Please acknowledge this limitation.
    Relevant content has been added at the end of the conclusion. Revisions are as follows:
    4.3. Limitations of this study
    In addition, although soil properties were strongly associated with differences in aboveground biomass among regions, the three study regions differed not only in soil properties but also in elevation, precipitation, soil type, and other environmental conditions. This study was unable to fully disentangle the independent contributions of soil factors and other environmental factors to vegetation productivity. Future studies should incorporate variables such as climate, topography, and long-term changes to further clarify the relative roles of different environmental factors in driving changes in grassland productivity.
24. 30-Line 388. The heading "6. Patents" is empty and should be removed if there are no patents associated with the study.
    
    
25. 31- Please standardize the use of "aboveground biomass" versus "above-ground biomass."
    It has been revised uniformly.
26. 32- Please standardize P-value formatting. Both P < 0.05 and forms using a different less-than symbol appear in the manuscript.
    It has been revised uniformly.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

Accept 

Author Response

We appreciate the positive comments from the reviewers on our manuscript.

Reviewer 4 Report

Comments and Suggestions for Authors

The authors have addressed almost all of the comments and evaluations I made on the first version of the paper, and the necessary revisions and addings have been successfully integrated to paper. Therefore, I believe the revised version of the paper is acceptable for publication.

Author Response

We appreciate your careful evaluation and positive comments on our revised manuscript. We are glad that you are satisfied with our revisions and modifications. Thank you again for your valuable suggestions, which greatly helped improve the quality of this work.