Influence of Species Composition and Management on Biomass Production in Missouri
Round 1
Reviewer 1 Report
The manuscript highlights the effect of species composition and crop management practices on biomass yield potential of perennial biofuel feedstock. Switchgrass was used either as monoculture or in combination with big bluestem in conjunction with mixture of forbs and legumes. The biomass yield was evaluated at three different harvest periods and two cutting heights of 15 and 30 cm respectively.
The results showed that the average biomass yield ranged from 2.82- 7.18 Mg ha-1 over a period of 4 years. There was no significant difference observed in biomass yield when perennial feedstock mixture was grown in conjunction with forbs and legumes. The average biomass yield recorded for three different time periods showed the higher yields in the month of July. A significantly higher biomass yield was obtained from the 15 cm cuttings in comparison to 30 cm cuttings.
The manuscript is well written. The results are discussed in detail. While there was no significant difference in biomass yield with different mixtures in conjunction with forbs and legumes, the study points out the possibility of obtaining diverse vegetation with minimum input by selecting site specific species. In addition, landowners can alter the timing of a harvest either for the use of biomass production in the late fall or spring or by haying or grazing for a livestock forage during the summer season.
Lines 2- 3: While the title is quite right, it would be clearer if a minor edit can be made “Influence of Species Composition and Management on Perennial Feedstock Biomass Production in Missouri”
Line 11 : Consider writing “ Perennial biofuel crops help reduce ……
Line 14: Consider deleting “plantings”
Line 20: Check for consistency. Line 125 and other places it is July, October, March
Line 21- 23: It will be a good idea to discuss average over 4 years and the minimum and maximum over 4 years as well.
Line 23: “The species mixture effect” can be rephrased. It can be confusing sine it was described earlier in the text.
Lines 109-110: Consider rephrasing “grass to forb+legume ratios”. It can be confusing for some readers.
Line 130: “three replicate plot” seems confusing. Consider rephrasing.
Line 130: Not sure if regression values were reported in the manuscript.
Line 172- 175: How the average values were obtained? Are these plotted in the Figure 2. As suggested earlier, it would be giving more clarity if discussed for 4 years duration rather than 2011 or 2013 only.
Lines 172, 191, 240, 262: While average and mean may be same but “mean was not used in the running text in the manuscript.
Author Response
Reply to Comments from Reviewer #1:
Lines 2- 3: While the title is quite right, it would be clearer if a minor edit can be made “Influence of Species Composition and Management on Perennial Feedstock Biomass Production in Missouri”
Thank you for the suggestion. We prefer to keep the short tile as it explains the study and as you also have agreed.
Line 11 : Consider writing “ Perennial biofuel crops help reduce ……
Thank you for the suggestion, edited as suggested.
Line 14: Consider deleting “plantings”
Thanks a lot for the good suggestion, deleted.
Line 20: Check for consistency. Line 125 and other places it is July, October, March
Thank you for catching this error. We have checked and corrected the issue.
Line 21- 23: It will be a good idea to discuss average over 4 years and the minimum and maximum over 4 years as well.
Thanks. Included in the abstract (5.21 Mg ha-1 during the study).
Line 23: “The species mixture effect” can be rephrased. It can be confusing sine it was described earlier in the text.
We have edited the sentence to improve readability. Thank you.
“The effect of species mixture was not significant on yield.”
Lines 109-110: Consider rephrasing “grass to forb+legume ratios”. It can be confusing for some readers.
We have revised the sentences to improve the readability. “The grass to forb and legume species ratios used in the plantings were:”
Line 130: “three replicate plot” seems confusing. Consider rephrasing.
Thank you for the suggestion. We have edited this section.
Line 130: Not sure if regression values were reported in the manuscript.
Thank you for the suggestion. We have edited this section.
Line 172- 175: How the average values were obtained? Are these plotted in the Figure 2. As suggested earlier, it would be giving more clarity if discussed for 4 years duration rather than 2011 or 2013 only.
We used those harvest yields to estimate means for figure 2. We have also included errors bars in the figure.
Lines 172, 191, 240, 262: While average and mean may be same but “mean was not used in the running text in the manuscript.
Thanks again. We have changed the term “average” to “mean” on Lines 21, 134, 140, 144, 147, 172, 224, 258, 265, and 325.
Reviewer 2 Report
I have several concerns:
In the abstract the authors refer to the ratios of base to native forbs plus legumes. No where throughout the manuscript do they document the actual ratios. They need to provide density counts at a minimum before they can make inferences regarding the differences in the ratios. Just because they planted them doesn't mean that is what's in the plot. They look at the difference between 15 cm and 30 cm stubble height. You would expect the 15 cm stubble height to have greater forage DMY than the 30 cm cut. Which is what they found. What would be beneficial is to look at the quality differences in the two cuts. Nothing really new reported here. Ln 62 they refer to monocrop yield after a decade … they need to tell us what the plant species is. The same on lns 63-64. lns 85-86 the authors refer to maturity scores of R3 and R5 they need to define those since most readers will not know what they are referring to. ln 94 the justification for the study is that it has not been done on 'claypan soils' they need to let the reader know why these soils are so different and important. lns 125-126 the authors refer to plots being harvested separately in July, …. was the entire plot harvested? Was it stockpiled forage or regrowth? How large was the dry-matter sample that was taken? Also what type of a harvester flail or cutter bar? Table 1 and figure 1 seem redundant. lns 301-302 they did not monitor mixture composition and natural reseeding of legumes and forbs of this nature is not enough to increase stand density. I found it very confusing that they referred to the harvests sequentially instead of with in years and maturity dates.
Comments for author File: 
Comments.pdf
Author Response
Reply to Comments from Reviewer #2:
In the abstract the authors refer to the ratios of base to native forbs plus legumes. No where throughout the manuscript do they document the actual ratios. They need to provide density counts at a minimum before they can make inferences regarding the differences in the ratios. Just because they planted them doesn't mean that is what's in the plot.
These ratios were defined in the abstract (L 19), methods section (L 110), results and also in figures.
We agree with your comment on changing composition with time. We have not estimated density counts to include the requested information.
They look at the difference between 15 cm and 30 cm stubble height. You would expect the 15 cm stubble height to have greater forage DMY than the 30 cm cut. Which is what they found. What would be beneficial is to look at the quality differences in the two cuts.
Thank you for the constructive comment. Yes, we have evaluated quality differences in biomass by harvest time and height for studied forage ratios of the study. We are developing a separate manuscript using results on quality differences among species ratios and cutting heights and hopefully it will be published in 2020.
Nothing really new reported here. Ln 62 they refer to monocrop yield after a decade … they need to tell us what the plant species is.
The list of species we used in the study and their ratios were explained (Lines: 19, 107-119, in results and figures). The species list may be found in this URL (https://science.sciencemag.org/content/sci/suppl/2006/12/12/314.5805.1598.DC1/Tilman.SOM.rev1.pdf)
The same on lns 63-64. lns 85-86 the authors refer to maturity scores of R3 and R5 they need to define those since most readers will not know what they are referring to.
Thanks for the suggestion. We have defined those stages in the revised manuscript. “panicle fully emerged from boot to postanthesis”
ln 94 the justification for the study is that it has not been done on 'claypan soils' they need to let the reader know why these soils are so different and important.
Thanks for the nice comment. We have inserted additional information on claypan soils. “Claypan soil are characterized by a dense impermeable clay horizon with very low hydraulic conductivity and greater runoff potential thus removing sediment and nutrients from agricultural watersheds.”
lns 125-126 the authors refer to plots being harvested separately in July, …. was the entire plot harvested?
This information is provided on lines 123-125.
Was it stockpiled forage or regrowth? How large was the dry-matter sample that was taken?
This was regrowth from the previous July harvest. The same sample size as before and the entire plot was harvested.
Also what type of a harvester flail or cutter bar?
This information is provided on lines 125-127. We have constructed a forage harvester for the study to more correctly harvest each plot (L 125-127). The following citation describes about the harvester.
https://acs.confex.com/crops/2006am/techprogram/P26010.HTM
Benton Naylor, Robert L. Kallenbach, Donald W. Harby, and Danny J. England. 2006. ASA-CSSA-SSSA 2006 International Meetings. November 12-16, 2006. Indianapolis, USA,
Table 1 and figure 1 seem redundant.
Table 1 provides long-term mean rain fall and during the study by year and growing periods. Figure 1 shows the monthly rain fall, deviation from the long-term monthly values and the cumulative deficit as the study continues from 2010 to 2013. Also the effects of temperature. And we sincerely believe this information is useful for the reader.
lns 301-302 they did not monitor mixture composition and natural reseeding of legumes and forbs of this nature is not enough to increase stand density.
Agree, yes, we did not monitor as explained earlier.
I found it very confusing that they referred to the harvests sequentially instead of with in years and maturity dates.
Thanks for the comment. This study was designed to study (1) effects of three harvest times; for biofuel in March, Forage in July and both in October and (2) two cutting heights to evaluate multiple benefits of growing biomass crops including for biofuel, forage, and both. Harvest times were determined by growth and needs (like forage, when low). In addition, landowners can alter the timing of a harvest either for the use of biomass production in the late fall or spring or by haying or grazing for a livestock forage during the summer season.
Reviewer 3 Report
I've provided a road map to publication via sticky notes in the attached pdf. The breakdown of precipitation in the Results section should be condensed.
Comments for author File: Comments.pdf
Author Response
Reply to Comments from Reviewer #3:
L20: We have included months and years for the establishment of the study and harvest data collection periods in the abstract. “The study was established in 2008 and biomass harvest data was collected from July-2010 to July-2013.”
L 20: This sentence was edited to improve readability. “Three harvest times were selected to represent (1) biomass for biofuel (March), (2) forage (July) and (3) forage and biomass (October).”
L 26-27: As suggested this sentence was removed from the abstract. “Annual precipitation was 6%, -28%, -38% and -13% different than the normal of 1083 mm for 2010, 2011, 2012 and 2013.”
L36: Deleted the term “nation’s” as suggested
L37: Edited to read as “Midwestern United States”
L42: We have included this information in the revised version. Planting perennial grasses has numerous ecosystem services, including reduction of non-native species [4].
L59: More good ecotype citations: Production of Autopolyploid Lowland Switchgrass Lines Through In Vitro Chromosome Doubling
Yang, Z., Shen, Z., Tetreault, H. et al. Bioenerg. Res. (2014) 7: 232. https://doi.org/10.1007/s12155-013-9364-x
Johnson, L.C., Olsen, J.T., Tetreault, H., DeLaCruz, A., Bryant, J., Morgan, T.J., Knapp, M., Bello, N.M., Baer, S.G. and Maricle, B.R. (2015), Intraspecific variation of a dominant grass and local adaptation in reciprocal garden communities along a US Great Plains' precipitation gradient: implications for grassland restoration with climate change. Evol Appl, 8: 705-723. doi:10.1111/eva.12281
Thank you for the information.
L66: due to a portfolio effect where one species lack of performance is substituted by another species. This effect has been highlighted by Tilman's biodiversity work.
The comment is not clear. We have included the benefits of diverse biomass species mixtures including legumes for biomass, forage, forage+biomass, soil enrichment (nutrients, erosion reduction, ..) by legumes and other species, and wildlife.
L67: legumes and forbs or leguminous forbs?
Legumes and forbs, some forbs are not legumes.
L69: citation? Grazer Ecology note covers this"
https://pdfs.semanticscholar.org/923e/956164532ef39656580b7349e967010f53cd.pdf
Thanks a lot.
L96: Could you introduce why cutting height or time may be an important factor foe inclusion in this study?
Thanks for the comment. As suggested, we have included new information on cutting height in the revised version. “Higher cutting heights were compared as they are important in order to preserve species richness and provide more food and cover for wildlife during the winter.”
L106: Which ecoslogical site does this study are arepresent? see
https://www.nrcs.usda.gov/wps/portal/nrcs/main/national/technical/ecoscience/desc/
cite like in study area section of Porensky et al. 2017:
Porensky, L. M., J. D. Derner, D. J. Augustine, and D. G. Milchunas. 2017. Plant community composition after 75 yr of sustained grazing intensity treatments in shortgrass steppe. Rangeland Ecology & Management 70:456-464.
We have included the ecological region of the study site in the revised version. Central Claypan Region 113. Also included a citation (USDA-NRCS 2006. land Resource Regions and Major Land Resource Areas of the United States, the Caribbean, and the Pacific Basin. USDA Handbook 296. Thank you for the information.
L133-164: Combine paragraphs. I think it is better to keep these 3 paragraphs as it is. Because these 3 paragraphs explain 3 different data types: (1) paragraph 1, Annual and growing period rain (2) paragraph 2, about monthly, and (3) paragraph 3, about the rainfall deficit.
L179: Deleted the word “has” as suggested.
L201: Deleted the word “has.” Thanks
L313: Included Schultze et al as suggested. Thank you.
L327: In general, citations are not used in the conclusions section and therefore we did not include citations in the conclusions section.
