Improved Estimation of Aboveground Biomass of Disturbed Grassland through Including Bare Ground and Grazing Intensity

Round 1

Reviewer 1 Report

I think that the study is newly work in this field and the nicely work. I have just few comment.

1. Can you add more explanation about UAV images and biomass sampling of results in your study?
2. It is good if you change the improve your study area’s map of elevation and region map

 

Author Response

 

 

Author Response File: Author Response.pdf

Reviewer 2 Report

The manuscript is well performed and the authors are aware of the limitation of their investigations. I have a minor concerns that may be explained in the text. It refer to when the pika was released and how the pika distrubance previous to the experiment was controlled and for how long pika activity resulted in the specified pika density?

Author Response

 

 

Author Response File: Author Response.pdf

Reviewer 3 Report

This manuscript describes a field study looking at detection of grassland biomass using UAV-based VI and experimental grazing regimes with mowing and rodent densities. It is a very good study, well carried out, and very interesting. The Figures a good. 

Although the first part is it is mostly well written, the narrative fails to clearly define the results and benefits as the Results section is very difficult to follow and seems to confuse the story which appears to be clear from the Figures. Then the Discussion section is poorly written with some very confusing and poor phasing.

As a result the manuscript will need major revision before it can be considered for publication.

The following are some points the authors need to address.

Need to explain the rodents better (pikas). These rodents need a Latin name and their significance and characteristics need to be better explained.

Figure 1. Small plot image annotation better in white font. Black font is hard to read

line 172 I think you mean "plant material"

BMM appears in the abstract and then at line 238.  It is important and not introduced properly. I can't see where there term is explicitly explained before it is referred to in passing. This causes confusion to the reader.

Further where is this described (MFRGBVI+BMM model). It is not clear from the narrative what you are doing here. It is like there is a section of Methods missing. And this is key material. You do describe the ???????.

So line 303 "It was worth noting that RMSE increased after BMM inclusion" does not mean much because the reader does not know what was done other than a mysterious bare ground factor was applied.

The Results section gets pretty complicated with all sorts of comparisons and a mixture of statements that seem to contradict: "MFRGBVI models achieved a remarkable accuracy of R2 ranging from 0.69 to 0.82 for both regression methods." and "Furthermore, the inclusion of BMM in the model (MFRGBVI+BMM model) further improved the accuracy by 0.05 up to 0.08, with the highest R2 being 0.86 and 0.88 for 2018 and 2019, respectively" and then "Nevertheless, although all the groups had little improvement after both F and BMM modifications in both years, the average value of ME was reduced to close to zero." The message from the results gets a bit buried in the weeds. The Figures seem to speak for themselves, provided the reader understands the F modification and the BMM modification and also accepts the validity of these. There is a lot of jumping about between comparisons and different factors and comparisons of errors versus fits and Rsquare. It really needs to be made clearer and more structured so the reader gets the message. At the end of it I am not sure from the text that the results are good, whereas the Figures suggest that they are.

Line 312. What are "vegetation conditions"?? The narrative throws masses of terms at the reader and lots of acronyms and lots of numbers. This reviewer is not clear from the narrative what section 3.3 is about. It just causes more confusion to the reader. Does section 3.3 matter?

Given the complexity in the current Results section, the Discussion needs to start with a few clear statements about the findings. i.e. what does the reader need to take from the Results section. After that you can discuss the grazing modifications and model approaches. At present the way the Results are written it seems that the authors are not entirely clear about the main findings.

The Discussion also contains some really vague and non-sensical statements e.g. "However, even after taking into account grass height, the regression models never achieved a perfect accuracy. In fact, the relationship between grassland vegetation height and AGB is rather loose. Results from the Hulunber grassland  demonstrated an R² of only 0.34 [88]. Although grassland AGB was loosely related to plant height, it has a good relationship with stocking rate and grazing intensity (R2 > 0.72) [56,57]. This relationship can be explained by that grazing had an effective influence on  the vertical structure of biomass by removing biomass equivalently and producing a uniform, smooth horizontal biomass distribution [89]."

"perfect accuracy"???? "relationship between grassland height and AGB is rather loose"??? And the last sentence above just does not make sense.

As a result, I cannot, based on reading the manuscript, agree with the opening of the Conclusion section since I don't have a clear idea of what the main findings were.

This is all a pity since I think it is a good study and very interesting. However, the authors get bogged down with too much analysis of errors and factors and throw numbers and acronyms at the reader when a clearer simpler narrative that speaks to each Figure in turn would be much better. Finishing the Results with the "vegetation conditions" analysis just obscures the message.

Please revise the Results and Discussion to provide a clear narrative and set of findings. Then maybe the statement at the beginning of the Conclusions will be self evident.

Author Response

 

 

Author Response File: Author Response.pdf

Round 2

Reviewer 3 Report

Dear Authors

Your revised manuscript provides a huge improvement in clarity. The text is concise and direct and flows so much better including in the restructured Discussion. The explanation of the bare ground adjustment is clear.

Nice paper.

Recommendation: Accept as is.