Stability of C₃ and C₄ Grass Patches in Woody Encroached Rangeland after Fire and Simulated Grazing

Round 1

Reviewer 1 Report

The manuscript “Stability of C3 and C4 Grass Patches in Woody Encroached 2 Rangeland after Fire and Simulated Grazing“ reports on the response of a number of dominant grass species to long-term fire and clipping treatments at an experimental rangeland site. It is a well written manuscript, with a good experimental design and appropriate analyses. The results seem robust and the interpretation of the main responses well explained and plausible. The experiment reported on is the same as the one reported on in one of the references (Ansley, R.J., Moeller, A., Fuhlendorf, S.D. Pyric-based restoration of C4 grasses in woody encroached (Prosopis glandulosa) grassland is best with an alternating seasonal fire regime. Restoration Ecol. 2022, 30(8), e13644. https://doi.org/10.1111/rec.13644) and the results appear to be a more detailed, species-level examination of the functional group trends reported in that paper. However, it does appear that the results of this manuscript are sufficiently different to justify a separate publication.

Despite my positive comments of the manuscript, I do not feel it is suitable for Diversity, i.e. for a journal that is primarily concerned with “biodiversity concepts and applications, biodiversity assessment, and biodiversity preservation”. The study reported on is not a study of biodiversity. The ultimate aim, as stated in the Introduction, is to improve the supply of forage from rangeland, rather than preserve biodiversity. The majority of the plant diversity of the community studied would come from the diversity of forb species (as is the case for most grassland communities), but only the most common grass species were included in this study. And while the management intervention suggested by the results of the study would probably increase the biodiversity of the study system, this is not explicitly tested or even discussed. I therefore suggest that the authors rather submit to one of the many journals which are more aligned with this particularly study, such as International Journal of Rangeland Management, Restoration Ecology, or Applied Ecology. I think it would be accepted in such journals with only minor revision, although the length might have to be reduced. This could be easily achieved by taking out some of the detail in the Introduction and Discussion. I have also suggested a few minor edits in the attached .pdf

 

Comments for author File: Comments.pdf

Author Response

Reviewer 1

The manuscript “Stability of C3 and C4 Grass Patches in Woody Encroached 2 Rangeland after Fire and Simulated Grazing“ reports on the response of a number of dominant grass species to long-term fire and clipping treatments at an experimental rangeland site. It is a well written manuscript, with a good experimental design and appropriate analyses. The results seem robust and the interpretation of the main responses well explained and plausible. The experiment reported on is the same as the one reported on in one of the references (Ansley, R.J., Moeller, A., Fuhlendorf, S.D. Pyric-based restoration of C4 grasses in woody encroached (Prosopis glandulosa) grassland is best with an alternating seasonal fire regime. Restoration Ecol. 2022, 30(8), e13644. https://doi.org/10.1111/rec.13644) and the results appear to be a more detailed, species-level examination of the functional group trends reported in that paper. However, it does appear that the results of this manuscript are sufficiently different to justify a separate publication.

Despite my positive comments of the manuscript, I do not feel it is suitable for Diversity, i.e. for a journal that is primarily concerned with “biodiversity concepts and applications, biodiversity assessment, and biodiversity preservation”. The study reported on is not a study of biodiversity. The ultimate aim, as stated in the Introduction, is to improve the supply of forage from rangeland, rather than preserve biodiversity. The majority of the plant diversity of the community studied would come from the diversity of forb species (as is the case for most grassland communities), but only the most common grass species were included in this study. And while the management intervention suggested by the results of the study would probably increase the biodiversity of the study system, this is not explicitly tested or even discussed. I therefore suggest that the authors rather submit to one of the many journals which are more aligned with this particular study, such as International Journal of Rangeland Management, Restoration Ecology, or Applied Ecology. I think it would be accepted in such journals with only minor revision, although the length might have to be reduced. This could be easily achieved by taking out some of the detail in the Introduction and Discussion.

 

Response: We appreciate the helpful comments. However, we believe that this paper is appropriate for Diversity journal. This paper is not about increasing forage for livestock. As we state in the introduction, woody plant encroachment has caused a sharp decline in diversity of grass species. It so happens that many of those grass species that have declined - C4 mid-grasses - are inherently more productive than the grass species that remain. As such, this does indeed affect forage availability for livestock, but these structurally larger grass species are also critically important for many other ecosystem services, including habitat for many wildlife species. They also are major contributors to root biomass and carbon sequestration. All of these ecosystem services relate to “diversity.” While we agree with this reviewer that forbs comprise a good deal of floral diversity in grassland ecosystems, our goal in this paper was not to measure overall floral diversity. Instead, we wished to determine if we could increase diversity of the grass species component. We argue that increasing the presence of these structurally larger C4 mid-grass species would increase landscape structural heterogeneity that will likely lead to greater diversity of other herbaceous species, wildlife species, and other ecosystem services. However, our goal in this paper was first to determine if a variety of clipping and fire treatments could sufficiently suppress woody cover and the cover of structurally lower grasses such as Nassella to allow for the advancement of the inherently structurally larger C4 mid-grass species. We cannot ignore that the region of the SGP where we conducted our study consists primarily of private farms and ranches that depend on livestock grazing for livelihood. Similarly, much of native grasslands worldwide provide sustenance for humans primarily via harvesting grass biomass through livestock grazing.  

We did modify a few sections of the Introduction to lessen the impression some readers might have that this is a livestock forage study. This included re-working the beginning of paragraph 4. We also shifted the description of C4 mid-grasses from being “more productive” than Nassella and Buchloe, to being “structurally larger” to place greater emphasis on landscape structural heterogeneity. We also added a grass species list as an Appendix at the end of the manuscript. The list of C4 mid-grasses includes some species that are not highly valued as livestock forage but are quite valuable for wildlife cover, ground bird nesting sites, soil stability, wind erosion mitigation, carbon sequestration and other ecosystem services. We note this in the Discussion section of the revised manuscript. We also added more about changes in forb cover in the Discussion and Conclusions. While we did not measure forb species diversity, we hypothesize that an increase in forb cover likely resulted in increases forb diversity and overall floral diversity.     

 

I have also suggested a few minor edits in the attached .pdf

 

Response: We made the suggested changes that were in the attached pdf.

 

Reviewer 2 Report

This is an interesting and valuable study.  Analyses are appropriate.  However, presentation of results could be clearer.  Analyses, text for results and data display do not align well.  1) Data were analyzed 1992-1998, 1996-1997, 1998, and 1998-2000, but displayed as 1992-2000; 2) there is mention of main effects for which analyses indicate interactions.  If there is an interaction, then the effects of one factor depend on the level of another; 3) Figs 2, 3, 4, 5 are displayed as though there were 3-way interactions, but there were not for any of those data.  Displaying the 2-way interactions will match analyses and simplify comparisons and text descriptions.  Figs 6A, 7A and 7B indicate a few fire effects but fire was not significant for those data.  They could be simply presented in text for clipping effects.  In short, the data presentation is more complicated than is necessary and that probably hinders understanding by the reader.  Another alternative could be to work backwards from end-of-phase results.  If there was an effect at the end of a phase it may be of interest to see how that occurred over time.  If there was no treatment effect, is there still interest in year effects?

 

11 – diversity have

117 - and for C4 grasses, April to September.

118 – and 1991

133 – 3 replicate plots

178 – it is not clear why there is a parenthetical reference to 1993 after mention of a 1995 exception.

179 – how could it be measured in fall before summer fire unless it was a different growing season or summer fire was actually fall fire?

188 – data should have been analyzed as repeated measures.

190 - 3-way analysis of variance with the SAS mixed procedure… similar alteration for line 195

213 - average rainfall with the greatest

286 - is shown in Table S5

344 – analysis section does not mention tests comparing patch type.

430 - intercanopy spaces in dense mesquite stands

433-437 – redundant

461 – 1800s

479 - because of competition

482 - + 3WF, 3AF, and 2SFC fire treatments favored

493 - single yearly clipping event

551 - extend into gaps between

583-585 – switched citation style here and lines 590 and 659

Author Response

Reviewer 2

This is an interesting and valuable study. Analyses are appropriate. However, presentation of results could be clearer. Analyses, text for results and data display do not align well.  1) Data were analyzed 1992-1998, 1996-1997, 1998, and 1998-2000, but displayed as 1992-2000; 2) there is mention of main effects for which analyses indicate interactions.  If there is an interaction, then the effects of one factor depend on the level of another; 3) Figs 2, 3, 4, 5 are displayed as though there were 3-way interactions, but there were not for any of those data.  Displaying the 2-way interactions will match analyses and simplify comparisons and text descriptions. Figs 6A, 7A and 7B indicate a few fire effects but fire was not significant for those data. They could be simply presented in text for clipping effects. In short, the data presentation is more complicated than is necessary and that probably hinders understanding by the reader.  Another alternative could be to work backwards from end-of-phase results. If there was an effect at the end of a phase it may be of interest to see how that occurred over time. If there was no treatment effect, is there still interest in year effects?

Response: Figures 2-5 are displayed to simultaneously illustrate two significant two-way interactions: clip treatment x year and fire treatment x year, as the analyses in Table 2 show. Additionally, there are significant two-way interactions between clip treatment and fire treatment, especially for the starting species in each of the patches. The most efficient way to illustrate all three of these two-way interactions is shown in Figures 2-5. In addition, we believe it is very important to document trends in cover of these species groups through time, as shown in these Figures, so the reader can see exactly when the clip and fire treatments occurred in each treatment. To aid in interpretation, we added dotted lines to each of these figures to separate Phase 1 (1992-1998) and Phase 2 (1998-2000).  

This reviewer makes an excellent point regarding documentation of the main effects of clip, fire and year on C4 Mid-grass responses, as shown in Table 2. Thus, we added an extra Table (now Table 3) and text in the Results section to address this.

What is now Table 4 (formerly Table 3) shows the statistical analysis at a single point in time at the end of Phase 1 and reveals significant main effects of clip and fire treatments for many of the response variables. We agree with this reviewer that we should consolidate wherever possible. Therefore, we deleted Figure 6A and Figure 8. We combined what was Figure 6B and Figure 7B into a new Figure 6.  Figure 7A is now a single panel figure 7 and what was Figure 9 is now Figure 8. Regarding the new Figure 6, we feel it is important to visually display the striking contrast between Nassella and Buchloe responses within Nassella patches. It is also important to visually document in some situations the consistent responses that occurred across the wide variety of fire treatments employed in this study. We appreciate these suggestions as it significantly reduced the size of the manuscript.

 

11 – diversity have - Response: done

117 - and for C4 grasses, April to September. - Response: done

118 – and 1991 - Response: done

133 – 3 replicate plots - Response: done

178 – it is not clear why there is a parenthetical reference to 1993 after mention of a 1995 exception. – Response: we removed the parentheses and made a separate sentence.

179 – how could it be measured in fall before summer fire unless it was a different growing season or summer fire was actually fall fire? – Response: good catch - thanks. We combined too many separate thoughts into one sentence. We re-worded to indicate that cover was estimated in fall months prior to the winter fire treatments, but that for summer fire treatments, we measured cover a few days prior to summer fires.

188 – data should have been analyzed as repeated measures. – Response: the proc mixed procedure accounts for this. We added this explanation in the Methods with a more detailed description of the Proc mixed procedure.

190 - 3-way analysis of variance with the SAS mixed procedure… similar alteration for line 195 - Response: done

213 - average rainfall with the greatest - Response: this sentence was shortened

286 - is shown in Table S5 - Response: done

344 – analysis section does not mention tests comparing patch type. - Response: we added this to the analysis section.

430 - intercanopy spaces in dense mesquite stands - Response: done

433-437 – redundant - Response: we deleted the redundant portion.

461 – 1800s - Response: done

479 - because of competition - Response: we re-worded this sentence

482 - + 3WF, 3AF, and 2SFC fire treatments favored - Response: done

493 - single yearly clipping event - Response: done

551 - extend into gaps between - Response: done

583-585 – switched citation style here and lines 590 and 659 - Response: we removed the author’s names and re-worded the sentences.

Reviewer 3 Report

The topic of the article is relevant and interesting, addressing important theoretical and practical issues. Without going into the strengths of the article, I will express the most important points that I think need to be corrected.

1. The biggest weakness of the article, which makes it particularly difficult to read and analyse, is the use of English plant names. In scientific articles, it is generally accepted to use the scientific names of organisms, which most readers understand unambiguously, whereas vernacular names completely confuse the text and, after reading a few pages, it becomes unclear what is being discussed. Therefore, I strongly recommend that the entire text be rewritten and adapted for an international audience. 

2. Why are the authors of the article only now publishing the results of the study when the study itself ended in 2000? Although the delay in publishing the results is not a critical factor in the validity of the article, it is worth explaining at least briefly in the methodology. 

3. The methods of statistical analysis need to be supplemented and described in more detail. Moreover, the software used for the statistical analysis is not specified.

4. I think that the writing of the figures should be tidied up. In many cases (e.g. line 207: Annual precipitation was >20% above average in 5, and >20% below average in 2 of the 10 years since) I would advise to write the numbers in words, especially when there are many different numbers in a sentence. This makes it harder to know whether you mean five years or the fifth year. 

5. Why is there no indication of which species were considered C3 and which C4 grasses? This makes it difficult to even imagine what the results mean when reading the results. Such a list could be in the methodology section. The fact that such a list is in the Supplementary Material section does not make the paper easier to understand.

6. The whole text of the article is written in correct but very difficult language. As a result, it is necessary to decipher what the authors meant to say in the results (e.g. line 361ff: Three-way analysis of clip x fire x year during 1998-2000 revealed mostly significant main effects of clip, fire and/or year, a few 2-way interactions, and no 3-way interactions for buffalograss and Texas wintergrass patches). However, the complexity of the language does not make a scientific article more scientific, and readers put such articles aside and rarely try to decipher all the coded ideas.

7. I suggest that the conclusions be presented in a shorter form, with the main points clearly formulated.

I think that the article needs to be completely revised, and then it can be evaluated in detail. The material has a very high potential to become a valuable scientific work.

 

 

 

 

 

 

 

The language is correct, but the sentences are very complicated and unclear.

Author Response

Reviewer 3

The topic of the article is relevant and interesting, addressing important theoretical and practical issues. Without going into the strengths of the article, I will express the most important points that I think need to be corrected.

1. The biggest weakness of the article, which makes it particularly difficult to read and analyze, is the use of English plant names. In scientific articles, it is generally accepted to use the scientific names of organisms, which most readers understand unambiguously, whereas vernacular names completely confuse the text and, after reading a few pages, it becomes unclear what is being discussed. Therefore, I strongly recommend that the entire text be rewritten and adapted for an international audience.

Response: We converted to the scientific names of the organisms. We referred to the two main grass species in the paper, Buchloe and Nassella, by their genus name only.

 

2. Why are the authors of the article only now publishing the results of the study when the study itself ended in 2000? Although the delay in publishing the results is not a critical factor in the validity of the article, it is worth explaining at least briefly in the methodology.

Response: Shortly after the study was completed, our university had a major budget cut and I (lead author) was forced to change research direction. I spent the next 12 years (2003-2015) focusing on a different research area. I then assumed an administration position in 2016 at another university that totally consumed my time. While I was able to publish some of the results related to the current study between 2003 and 2010, I was not able to address this particular data set until recent years. The isolation brought on by the Covid pandemic actually allowed more time for this. These data have never been submitted to another journal. I thought, upon being invited by this journal to submit a paper that this study would be a good choice as it reveals grass species transitions at the micro-site level over a long time-period. Such a data set is unique, especially with the variety of seasonal fire treatments applied. I would prefer not to include in the manuscript any explanation as to the delay in publishing.

3. The methods of statistical analysis need to be supplemented and described in more detail. Moreover, the software used for the statistical analysis is not specified.

Response: We added more detail. The software was referenced in the initial submission but we provided more detail within the reference that included a web site address specifically for the SAS Proc Mixed procedure.

4. I think that the writing of the figures should be tidied up. In many cases (e.g. line 207: Annual precipitation was >20% above average in 5, and >20% below average in 2 of the 10 years since) I would advise to write the numbers in words, especially when there are many different numbers in a sentence. This makes it harder to know whether you mean five years or the fifth year.

 

Response: We have adjusted that line in question. We also looked over the paper and reduced the length of other long sentences.

5. Why is there no indication of which species were considered C3 and which C4 grasses? This makes it difficult to even imagine what the results mean when reading the results. Such a list could be in the methodology section. The fact that such a list is in the Supplementary Material section does not make the paper easier to understand.

Response: We added an appendix at the end of the manuscript that lists the major grass species at the study site. The site is mostly devoid of other C3 perennial grass species besides Nassella and we added that note to the site description section in the Methods.  

6. The whole text of the article is written in correct but very difficult language. As a result, it is necessary to decipher what the authors meant to say in the results (e.g. line 361ff: Three-way analysis of clip x fire x year during 1998-2000 revealed mostly significant main effects of clip, fire and/or year, a few 2-way interactions, and no 3-way interactions for buffalograss and Texas wintergrass patches). However, the complexity of the language does not make a scientific article more scientific, and readers put such articles aside and rarely try to decipher all the coded ideas.

Response: We divided this specific sentence into two sentences. As stated in the response to question 4 above, we looked over the rest of the paper and reduced the length of a few other sentences. It was necessary to include treatment descriptions in many of the sentences and since many of the treatments were a combination of clipping plus fire, this added to the complexity of the treatment description. Aside from the length of such descriptions (e.g., “clip + 3WF treatment”), or the description of a variable within a grass patch (e.g., “C4 mid-grass cover within Buchloe patches”), most sentences throughout the manuscript are very straightforward.     

7. I suggest that the conclusions be presented in a shorter form, with the main points clearly formulated.

Response: We completely reworked the Conclusions, moving some material back to the Discussion and simplifying the focus of each paragraph in the Conclusions. We also better linked the points in the Conclusions to those brought up in the Introduction.

I think that the article needs to be completely revised, and then it can be evaluated in detail. The material has a very high potential to become a valuable scientific work.

Response: We appreciate the comments and made many changes to help simplify the text.

Round 2

Reviewer 3 Report

The article has been substantially revised and improved following the comments of the reviewers. The comments have been taken into account or responded to with reasoned answers. I have no additional substantive comments on the content of the article. 

Minor editorial corrections are needed.