The Impact of Grazing on the Grass Composition in Temperate Grassland

Round 1

Reviewer 1 Report

The manuscript 871904 „The impact of grazing on the grass composition in Temperate Grassland“ aims to analyzed  the  effects  of  grazing  intensity  on  grassland vegetation (78 plant species and eight plant functional groups, during  four  grazing  seasons. The study analyses four levels of grazing intensity;  control, light, moderate, and  heavy grazing intensity corresponding to 0.00, 0.23, 0.46 and 0.92 Animal Units ha -1  respectively. Vegetation species where separated into different groups; functional (grass, herbs, …), water needs (mesophyte,…), digestibility (palpability) and grazing/niche tolerance (Compensators, increaser, randomer…) and furthermore “abundance patters” in order rank effects of grazing intensity over time. Results show that each plant functional group showed a different response to grazing intensity. E.g. perennial tall grasses characterized by high palatable mesophyte and mesoexerophyte grasses declined grazing intensity, while the medium palatable xerophyte and widespread  grasses such as predominant perennial short grass, increased with grazing intensity. Gazing intensity also affected soil factors (soil nutrient, soil moisture, and soil temperature and soil bulk density) which modified some functional groups, such as tall fescue and Liliaceae, where as some groups where neither affect by directly grazing (defoliation) nor soil environmental changes caused by grazing activities.

I did like the study and the combination of different classifications (rankings) and analyses to describe the vegetation (and change). To my opinion the study provides useful information to i) create grazing management scenarios and ii) conduct adaptive practices to maintain conciliate ecological functions with production.  The data set is interesting and worthwhile to be published, however, not in the present form.

Introduction would need revision, as a number of phrases seem to come from nowhere, or seem to be an alignment of copied phases from elsewhere. Introduction should introduce the story (the heart of the paper) meaning show what is know and what in unknown or would need further research to clarify.

L 36-38 “Grazing is not only a concern in Inner Mongolia but also in all the grasslands of the world. Its  impacts on plant species are not solely due to animals’ selective grazing behavior, but additionally  as a result of the tolerant of the plant to grazing density, which leads to a decline in biomass as the  livestock rate increases”

Grazing is not only a concern in Inner Mongolia but also in all the grasslands of the world. Grazing  impacts not only plant species by defoliation and selective grazing behavior, but also by mechanical pressure (trampling), which lead all together to a decline in biomass as the  livestock rate increases”

-The different ranking, (i.e. the different plant groups and way how to classify species)  was not introduced (e.g. functional (grass, herbs, …), water ecotypes   (mesophyte,…), digestibility (palpability) and grazing/niche tolerance (Compensators, increaser, randomer…)

Material and Methods  need some calcification and more detail in most of the sub sections. E.g. the study site “Hulunbeier grassland” was written in different ways (Hulunber area, Hulunbuir grasslands)?

Suggest to add when the growth period happens (L107-113)

Suggest to mention the cumulative rain (annual precipitation sums) of the study years (either in the Fig 1. or in the text).

The experimental description is confusing for the reader… please see the specific comments.

The estimation of the important value of plant species (IV)  is not clear to me. The density of an individual was obtained by counting on each quadrat, so this is in %( on the basis of 100) . What is the difference to relative coverage (RC). Relative biomass is (RB) is also in %?

If I got right RD mean of 5 quadrates, RC is species abundance per quadrate and RB is the biomass to the total biomass per quadrate.

What is then the important value( I_V) is also the sum Σ ( RC(%) + Rd(%)  + RB (%)) /3. Meaning when the value is high the species is important and visce versa?

Personally I would have used  RC/RD *RB. As you can have a very common species (high coverage) which is very light, OR a very rare species but heavy weight. Please explain better with the units!

Please detail soil sampling, reader has not information on depth, diameter of soil cores… please describe what are the measurements with  analyser Mastersizer 2000 laser particle size analyzer (0-2000 μ m).

Please detail how daily feed intake was estimated.

Please detail data analyses and the ranking, e.g. functional (grass, herbs, …), water ecotypes  (mesophyte,…), digestibility (palpability) and grazing/niche tolerance (Compensators, increaser, randomer…).

Please detail the Bray-Curtis index used for similarity pattern recognition in the data analyses.

Please add details to draw Fig 7 dominance value and the time periode which was used to determine and decline or increase.

Results

Please detail how you determined Table 1 and ranking

L 217 and 405ff. mentions soil environnement changes. These data is not shown in the manuscript neither explained in the MM… do authors have data on these measures?

Figure  7.  Species change  pattern  along  grazing  succession.  (ID = Species  dominance  increased  in  light  grazing  and  then  declined  in  higher  grazing  intensity,  II  =  Species  dominance increased along grazing gradient, FL = Species dominance fluctuated stable, RA = Species  appeared randomly in community, RARE = Species appeared only once in the research period)

The measure is not clear. Seems that Authors have ranked functional groups according to the decline or increase of the time. Using a dominance value which was not explained?!! OR is the species abundance?  Besides reader has no idea on the time scale… after 1year after 3 years …. Not clear and was not explained in the MM section

Figure  8.  Relationship between plant functional groups and species change patterns in succession. used soil bulk density; soil moisture;  soil temperature; however the MM to get this number was not shown neither the results?

Discussion

The discussion would need revision, to tell the story (the heart of the paper) meaning show what is NEW and unknown and how can we use the results to explain mechanisms or effects of grazing intensity on vegetation cover.   I also suggest to use all the results, it seems that authors do  barely use the “advanced “ figures 6 and 7 to draw their conclusion. Large part are repeats of the results without any explanation what we can learn from the study, what is new and what can we conclude.

L394 “The results showed that community stability was related to the resilience of species, but not  o the resistance of plants.”  Authors did not mention resilience /resistance in the introduction neither in the MM and neither what is their definition of these terms and on what data this is based!

Conclusion

L423fff “The result of this study would considerably contribute to managing the grassland of the study area sustainably” I think the results "can" contribute and authors "can" conclude or "suggest"  or "recommend"…

Specific comments

L44-47? Not clear

L48-51? Not clear

L51  However, in systems with grazing exclusion non-grazing could result in a decrease or slight modification in species diversity…

L 53 To this fact, when considering a land management mosaic, Moreover, the integrative changes in plant diversity may not co-occur across the all grassland systems land subjected to

L74-77 is a repeat and should be moved to L51

L99 grazing compression and topography were variables… Not clear.

L101… were calculated based on the important value…. Which?

L122-128 Experiment was setup in a split plot design with three replicate paddocks (each 167x300m) per grazing treatment (fig. 2).  Four grazing intensities were tested; control, light, moderate and high ( with an animal number of 0, 2, 4 and 8 young cows, with a weight  of 250-300 kg).  Considering an  animal unit equals 500kg adult cattle the treatments corresponded 0.00, 0, 0.23, 0.46 and 0.92 animal units  (AU) / ha (i.e. G0.00, G0.23, G0.46 and G0.92 respectively). The grazing animals were kept in the pasture day and night, and outside water source was used to supply them with drinking water. Grazing period was from June to October, and lasted for 120 days every year. Accordingly three replicate paddocks were used for each grazing intensity and covering a 5-hectre paddock, 12 paddock, randomly distributed over a uniform total area  of 600 hectares.

L136-144 need revision . I suggest to word :

Above ground biomass (AGB) was measure at peak of biomass at the beginning of August in 2014, 2015, 2016 and 2017. AGB was determined by measuring five random samples (1m2)  selected in each grazing area. In each sample quadrat, species composition, canopy height and coverage were measured.  The coverage was determined using a 50 x 50 cm grid with and 100 crosshairs (each grid cell 5x5cm?). The natural heights of plants were measured by the straight edge multipoint method and the average value was taken.

The density of an individual was obtained by counting (Not CLEAR, SUM, MEAN?) on each quadrat. The crown is then cut pruned on the ground level and separated for each species or life form group. The separated biomass was dried at 65 ℃ for 48 hours to constant weight. The important value of plant species (IV) was calculated as followed.

L249-252  Most of the compensatory (ID), fluctuated stability (FL), please explain the letters…

mesoxerophye (Fig. 7d). Figure 1. symbol legend has errors (°C)  and temperature…

L 265 “We  used  CCA  to  analyze  how  the  community  parameters  change  along  with  the  grazing intensity” what was the time period of the data… all data or one year, last year... please detail

L306. “Our results indicated that there are non-significant differences in species abundance species number (?) among the  different grazing intensity (Fig. 3c). L308 and figures 7 does not show the same, and even shows changes in abundance. So please avoid discussion points on basic results… I recommend to use the basic results say that species number does not give any indices on ecosystem functioning which abundance and ranking of functional groups, water ecotypes, palapltibilty is much more detailed.

L337 In this study, we classified species into eight major PFGs based on the relevant trait response to… What are the traits? not clear.

L369ff. “There is an optimal grazing intensity to maintain the structure and  function of ecosystems[9], Heavy grazing may reduce biodiversity and productivity [56] while light  grazing density may also lead to composition changes and species invasion [57]. Please name the optimal grazing intensity according to results! To my opinion it is moderate

L411 In this study, different sensitive indexes…. Which one?

Figure 3. please explain better (Cover%) and (species richness m2) this is not in the MM section.

Figure 4. not easy to understand… can you please explain the figure axis.  

Table 1 what is the column with  No.?

Figure  8.  SBD: soil bulk density; SM: soil moistur

Author Response

Dear editors and reviewers:

Thank you very much for your careful review and constructive suggestions with regard to our manuscript “The impact of grazing on the grass composition in Temperate Grassland” (ID: Agronomy-871904). Those comments are helpful for authors to revise and improve our paper. We have studied comments carefully and tried our best to revise and improve the manuscript and made great changes in the manuscript according to the referees’ good comments. Revised portion is marked in red in the paper. We appreciate for Editors/Reviewers’ warm work earnestly, and hope that the corrections will meet with approval. Please feel free to contact us with any questions and we are looking forward to your consideration. The main corrections in the paper and the responds to the reviewer’s comments are as following:

Author Response File: Author Response.pdf

Reviewer 2 Report

explore the species-specific response of grazing. I found their study well conducted and interesting. I have some smaller issues below that resolve around clarity. However, there are two larger issues I’d like to address.

The first is around the writing. The language of each sentence is largely correct, but structure in each of the paragraphs is missing. For example, the introduction has a few paragraphs that are one or two sentences long, and the story contained within jumps around quite erratically. I took the liberty of re-writing what I believe the first and last paragraphs of the introduction should be. I would request the authors apply this type of structuring throughout the rest of the introduction and manuscript.

First paragraph:

“Grazing is not only a concern in Inner Mongolia but also in all the grasslands of the world. Rainfall has been considered as a key factor in controlling productivity and determining suitable grazing intensity in temperate grassland [2. 3]. However, management policies for grazing can mediate the productivity of grasslands. Both the duration and intensity of grazing are important, controllable factors affecting the response of plant communities. For example, long-term grazing had an XXXX impact on grassland composition, whereas grazing intensity can have YYYY effect [2, 5]. Therefore, alternative management measures should be considered in order to optimize the grazing intensity and yield of Inner Mongolia grassland”

Last Paragraph:

“The process and mechanism of grassland degradation as a result of grazing intensity in Inner Mongolia is poorly understood. Therefore, the focus of this study was to explain whether the change of vegetation composition caused by grazing could be mitigated [18, 19]. We examined the effects of grazing intensity on plant functional group composition and clarified the potential response of herbaceous species to grazing intensity to find an alternative management strategy to conventional livestock husbandry. We conducted the experiment in Hulunber area (Noreth-east of Inner Monglia) under four grazing from control to heavy grazing, a controlled grazing experiment on the effect of cattle grazing on vegetation composation was established. This range of grazing intensities may be needful for a wide-ranging analysis of vegetation composition responses to grazing intensities [17,18]. The result of this study would considerably contribute to managing the grassland of the study area sustainably/”

My second issue is around the many smaller mistakes. There are small syntax or spelling errors that should be corrected throughout. Some examples below but please correct everywhere:

Line 55 – Delete the comma before the citation

Line 63 – deleted the space after the citation

Line 119 – a space needed after “2009,”

Line 121 – There are extra apostrophes when no values are in between.

Line 124 – Needs a period where the comma is.

Line 150 – Need a little more information about soil collection. Was it dried? How was it stored and for how long? Was it sieved? Was any organic particulate removed?

Why are some periods the colour red?

Methods

I don’t agree with the calculation of the IV. The issue is that reach of the three values that are being compared are different. Coverage is a percentage, density can be a number between zero and infinity, and biomass can also be an unbound number. I believe each of these should be percentages where it is each of these values for each species divided by the total value across all species. Perhaps that is what is already being done with the term “relative” but it is unclear to me if that is the case.

e.g IV = (RC/AllCoverage + RD / AllDensity + RB / AllBiomass) /3

Results:

Lines 276 & 279, what are DD and RA? You define them, but then just use that definition?

All figures: Can you create a consistent format. Such that they all use the same colour palellete and have the same design (e.g. boxes closed vs open).

Figure 1: Temperature, precipitation, and average are each spelled incorrectly. Please remove the lines separating the months. It makes it hard to read.

Figure 2: move to appendix

Figure 3: “Above” in above ground is spelled incorrectly.

Figure 6: Move the names in the figure caption directly into the figure legend. For example, instead of putting “M” write out mesophyte.

Figure 7: Instead of reporting this as a figure can you report it with some form of statistical test. A GLM with fit to a binomial family to account for the percentage data might make the most sense. Then move this figure to an appendix and simply report the statistical outputs in place of where you are referring to the figure. The graph identifies the differences but too many figures I believe complicate the story.

Author Response

Dear editors and reviewers:

Thank you very much for your careful review and constructive suggestions with regard to our manuscript “The impact of grazing on the grass composition in Temperate Grassland” (ID: Agronomy-871904). Those comments are helpful for authors to revise and improve our paper. We have studied comments carefully and tried our best to revise and improve the manuscript and made great changes in the manuscript according to the referees’ good comments. Revised portion is marked in red in the paper. We appreciate for Editors/Reviewers’ warm work earnestly, and hope that the corrections will meet with approval. Please feel free to contact us with any questions and we are looking forward to your consideration. The main corrections in the paper and the responds to the reviewer’s comments are as following:

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

I appreciate the authors efforts in revising their manuscript. They have made extensive edits and the paper now reads much better.

My only comment is that there are still many small grammatical or spelling errors that need to be addressed. I list a few examples, but I ask the authors to review the whole manuscript and address them all:

Line 17 - Need a space between "9" and "species"

Line 38 - Quotation marks should be removed

Figure 1 - Precipitation and temperature are both misspelled in the legend

Author Response

Dear editors and reviewers:

Thank you very much for your careful review and constructive suggestions with regard to our manuscript “The impact of grazing on the grass composition in Temperate Grassland” (ID: Agronomy-871904). Those comments are helpful for authors to revise and improve our paper. We have studied comments carefully and tried our best to revise and improve the manuscript and made great changes in the manuscript according to the referees’ good comments. The revised portion is marked in red in the paper. We appreciate for Editors/Reviewers’ warm work earnestly and hope that the corrections will meet with approval. Please feel free to contact us with any questions and we are looking forward to your consideration.

Best regards

Authors  

Author Response File: Author Response.pdf