Understory Vegetation Composition and Stand Are Mainly Limited by Soil Moisture in Black Locust Plantations of Loess Plateau
Round 1
Reviewer 1 Report
The theme of the manuscript is fairly interesting and there is no critical flaw in the research design as well as the data analysis. However the obtained results seem to be not sufficiently discussed. Therefore I would like to judge that major revision should be applied on the manuscript considering the following comments.
- There is an obvious discontinuity in the trend of vertical cover fraction components between 35 years and 40 years in Figure 3. Furthermore all of the three diversity indices almost coincide at the 35 year in Figure 4. Although these characteristics of the results, the authors provided no discussion on them. Appropriate explanation or discussion must be added concerting these points.
- Additionally on Figure 4, although detailed description was provided, the authors provided no discussion on the result concerning the difference between three diversity indices in relation to their definition and properties.
- On the result of soil properties summarized in Table 1, at first the multiple comparison method used was not described in the method section. Secondly, although in the result section the yearly trends of measured soil properties were explained, there was no discussion concerning each soil property characteristic. For example, it seems that only TP expresses different trend compared with other soil properties; appropriate discussion should be provided concerning such backgrounds.
That's all and I hope my comments will be some help for the revision.
Author Response
Point 1: There is an obvious discontinuity in the trend of vertical cover fraction components between 35 years and 40 years in Figure 3. Furthermore, all of the three diversity indices almost coincide at the 35 year in Figure 4. Although these characteristics of the results, the authors provided no discussion on them. Appropriate explanation or discussion must be added concerting these points.
Response 1: Very thanks for your valuable comments. In the revised manuscripts, we have added more explanation into the discussion (lines 240-245; 283-286).
Point 2: Additionally, on Figure 4, although detailed description was provided, the authors provided no discussion on the result concerning the difference between three diversity indices in relation to their definition and properties.
Response 2: Very thanks for your valuable comments. In the revised manuscripts, we have added more explanation into the discussion (lines 267-274).
Point 3: On the result of soil properties summarized in Table 1, at first the multiple comparison method used was not described in the method section. Secondly, although in the result section the yearly trends of measured soil properties were explained, there was no discussion concerning each soil property characteristic. For example, it seems that only TP expresses different trend compared with other soil properties; appropriate discussion should be provided concerning such backgrounds.
Response 3: Very thanks for your encouraging remarks and valuable comments. In the revised manuscripts, we have added the multiple comparison into the method (lines 140-141). More discussion has been added into the discussion (lines:277-282).
Author Response File: 
Author Response.docx
Reviewer 2 Report
Review of: Understory Vegetation Composition and Stand are Mainly Limited by Soil Moisture in Black Locust Plantations of Loess Plateau
For: Forests
January 2021
Summary
The authors examined the understory layer of areas being reforested with black locust plantations. They assessed the understory diversity and soil properties, relating the two. The results show species differentiation among the height layers, a reduction in low vegetation through time, variability in plant diversity through time, increases then decreases in soil fertility through time, and relationships between soil properties and plant diversity.
Strengths
This effort addresses an important landscape feature and an often overlooked layer of forests. The authors did a good job of capturing a wide range of classes in stand age and collected valuable data about the forest understory and soil conditions.
Weaknesses
The English needs improvement throughout. The authors could examine their data from a layer-community perspective to get a deeper assessment of the change within layers through time. We need more information about the soil horizons measured in the study.
Specific Suggestions
- The authors’ English is vastly better than my Chinese. That said, I encourage the authors to work with a colleague who is fluent in both Chinese and English to work through the grammar of the manuscript.
- I think the paragraph in the Introduction and the sentence in the Discussion about climate change can be deleted. Climate change is a valuable topic, but it is not pertinent to the subject of this study: succession of the understory layer in plantations.
- The authors could delve into the subject of which species (both in the canopy and understory) are native and which are not. Was there a change in percent native species through time? Were non-native canopy species planted? If so, why?
- A critical aspect of this study is the data from the soils. The authors report that they sampled from 0-20 cm, but we do not know what soil horizons this sampling included. Was it all among the O horizons? Did it get into the A horizon? Did this sampling of layers vary among samples or study sites? The soil characteristics presented in the study vary a great deal among these horizons, and we need to know exactly what was sampled.
- Given the data that the authors have, I am surprised that they did not do more analyses of the changes in species composition through time. For example, it would be valuable to know about changes in the Coefficient of Community Similarity from young to moderate to older plantations.
- What is the sample size at each stand age?
- Related to the sample size question, any variability in the soil horizons sampled at each site could have a dramatic effect on the soil properties within an age. There are 13 ages and 33 sites. If the A vs. O horizon was sampled more at a particular age, there would be important changes in the average soil traits within that age having nothing to do with stand age. Sample size and the horizons sampled are things that the reader needs to know.
Recommendation
I recommend that attention is paid to the (sometimes) major issues detailed above.
Author Response
Point 1: The authors’ English is vastly better than my Chinese. That said, I encourage the authors to work with a colleague who is fluent in both Chinese and English to work through the grammar of the manuscript.
Response 1: Very thanks for your valuable comments. Our manuscript has been Standard editing by a professional editor. If there is any language problem, we will modify it again.
Point 2: I think the paragraph in the Introduction and the sentence in the Discussion about climate change can be deleted. Climate change is a valuable topic, but it is not pertinent to the subject of this study: succession of the understory layer in plantations.
Response 2: Very thanks for your valuable comments. In the revised manuscripts, we’ve reduced descriptions of climate change. We only use climate change as a macro-environment for research and concern. (lines 54-56; 314-315).
Point 3: The authors could delve into the subject of which species (both in the canopy and understory) are native and which are not. Was there a change in percent native species through time? Were non-native canopy species planted? If so, why?
Response 3: Very thanks for your remarks and valuable comments. In the revised manuscripts, we have added more discussion about species change into the discussion. The change of native and invasive species is a valuable subject, we will explore the phylogenetic changes of species in the future studies. (lines 252-255).
Point 4: A critical aspect of this study is the data from the soils. The authors report that they sampled from 0-20 cm, but we do not know what soil horizons this sampling included. Was it all among the O horizons? Did it get into the A horizon? Did this sampling of layers vary among samples or study sites? The soil characteristics presented in the study vary a great deal among these horizons, and we need to know exactly what was sampled.
Response 4: Soils data is a critical aspect in this study. Very thanks for your remarks and valuable comments. In the revised manuscripts, we have added more detail on soil sampling in the methods section (lines 110; 123).
Point 5: Given the data that the authors have, I am surprised that they did not do more analyses of the changes in species composition through time. For example, it would be valuable to know about changes in the Coefficient of Community Similarity from young to moderate to older plantations.
Response 5: Very thanks for your valuable comments. In the revised manuscripts, we have added more analyses of the changes in species composition through time. We focus on different layers species change, so we did not use Coefficient of Community Similarity. This idea is well worth investigating further (lines 252-255).
Point 6: What is the sample size at each stand age?
Response 6: There were three sample at each stand age. Thank you for your comments. In the revised manuscripts, we have added detailed sample information (lines 110-111).
Point 7: Related to the sample size question, any variability in the soil horizons sampled at each site could have a dramatic effect on the soil properties within an age. There are 13 ages and 33 sites. If the A vs. O horizon was sampled more at a particular age, there would be important changes in the average soil traits within that age having nothing to do with stand age. Sample size and the horizons sampled are things that the reader needs to know.
Response 7: Very thanks for your valuable comments. Sample size and the horizons sampled are important things both for reader and researcher. In the revised manuscripts, we have added detailed sample information (lines 110-111; 123).
Author Response File: Author Response.docx
Round 2
Reviewer 1 Report
The previously commented points were appropriately revised. No other comments now.
Reviewer 2 Report
The authors have addressed the issues from the original manuscript. No other comments now.
