Influence of Environmental Factors on Species Richness and Diversity in a Semi-Arid Environment, South Africa

Round 1

Reviewer 1 Report

The manuscript "Influence of environmental factors on the species richness and diversity in the semi-arid environment, South Africa" was reviewed, and some suggetions were provided as follow. 

In section 2.3, only the method of landform parameters (slope and aspect) and spatial references were provided, but how did the author obtained the enviromantal factors, such as bulk density, cation, soil textures, nitrogen, rainfall, etc.?

Because of the small range of longitude and lantitude, it made no sense to anlyze and discuss the effect of latitude/longitude on richness and diversity in this study. 

Please provide the equation of normalized Shannon diversity index, or the caculation method.

Please provide the significance test results for each pariwise correlation coefficients.

The soil physical and chemical parameters of each plots must be provided base on the field sampling instead of extract from database.

It may be more interesting to analyze and discuss the vegetation characteristics in the Moutain Zebra National Park, and cmparing the differences between Albany Thicket, Grassland and Nama-Karoo.

Author Response

Good day Reviewer

I am grateful that you took the time to review my paper.

Author Response File: Author Response.pdf

Reviewer 2 Report

The manuscript entitled „Influence of environmental factors on the species richness and diversity in the semi-arid environment, South Africa” explores diversity patterns in the Nama Karoo biome. As the authors highlight, this one of the least studied biomes in the semi-arid region of South Africa. Even basic data on biodiversity are lacking. Thus, studies contributing to fill this gap in knowledge are highly welcome. The authors focus on two diversity measures – species richness and the normalized Shannon diversity index – of different vegetation units in Mountain Zebra National Park. Diversity measures are related to different environmental factors, to detect the variables with the highest explanatory power, and to provide a key reference, which environmental factors drive plant species richness and diversity in semi-arid environments in general. Due to the lack of biodiversity studies from the Nama Karoo biome, the study at hand has the potential to contribute new insights. However, I see a couple of points for improvements, which should be addressed by the authors prior to a decision about the suitability for publication in MDPI Grasses. As these points are both numerous and serious, I opted for reject, but I would like to encourage the authors to resubmit a thoroughly revised version of the manuscript to MDPI Grasses.

Formal points

Citation of references (author names and year) does not follow MDPI standards, which is by numbers in brackets [1], please change

L4: Nthabeliseni Munyaia,*, Abel Ramoelob and: I guess there are additional authors missing???

L5-11: affiliation of authors is not indicated

 

Major comments with regard to content

The study area description is poor. I would like to get more information about the elevational range and how the biomes present (i.e. Albany thicket, Grassland and Nama Karoo) are related to elevation. I recommend to add an overlay of contour lines to Figure 1 and Figure 2, or include a DEM as separate figure. I would also like to be informed about are the dominating species, vegetation structure, groundcover, etc. within the different vegetation units. Some photographs would nicely illustrate the different biomes and would give the reader a better impression of biomes covered in the paper. Also, the description of the climatic condition could be improved and better illustrated by climate charts.

Also, the description of the field data collection needs to be improved. Please provide a better description of the sampling methods, including how many plots were sampled in each of the different vegetation unit, what is the size of the plots, what is sampled (just presence/absence or any abundance measures), etc. The figure caption of Figure 2 indicates, that the figure shows the location of the monitoring plots, but it shows only the management units in the Mountain Zebra National Park

In section 2.4 Statistical Analysis please provide a better explanation of NSDI. In, addition besides species richness and species diversity of the different vegetation units it would be interesting to include additional diversity measures such as evenness within units/plots and beta-diversity between units as well as structural diversity measures (life-form, growth-form, biological traits). Also, multivariate statistical analyses should be included, to show the similarity / dissimilarity between different units and the environmental variables resposible. Including those aspects would give the paper much more significance.

In a paper about vegetation and plant species diversity I would like to be informed at least about the most common plant species. Currently not even one single plant species name is mentioned in the manuscript! I recommend to name at least the dominant plant species of the different vegetation units, and I also recommend to provide a species list, probably as supplementary material if too extensive to be included as Table within the main body of the manuscript.

Finaly, in the Introduction we are informed, that the area is heavily grazed, but further on, in particular in the discussion section this topic is not further treated. What about grazing and/or browsing intensity as factor for species richness and diversity patterns detected. Please include this factor in both the analyses and in the discussion of the results.

 

Minor remarks

L71-71: soil topsoil: bad wording

L73: diverge: better: varies

L 145: In Figure 3 it does not become clear to me, what is shown in the first chart (Aspect, Count), please explain.

L168-169: this sentence is Materials and Methods, and needs a better explanation for “east being the reference category”

L223-224: redundant, already presented in L202-203

Author Response

Good day reviewer

Thank you so much for reviewing my paper.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

In my previous review, I asked the authors to provide the source of data on climate and soil, but the authors only provided software to extract the data. Here, again, the author is asked to provide the source of the climate and soil data in this article, is it sampling form field, or extracted from a database, such as wosis, worldclim?

Author Response

Good day reviewer, thank you so much for your comments and I have responded to them on the Word document.

Author Response File: Author Response.pdf

Reviewer 2 Report

In the revised version of the manuscript entitled „Influence of environmental factors on the species richness and diversity in the semi-arid environment, South Africa” the authors reasonably addressed some of my concerns raised in the first round of review, such as formal aspects (e.g. MDPI citation style) or providing more information on the study area or including some basic information about species composition of the biomes studied. However, other recommendations made by me as well as by another reviewer were disregarded without a meaningful explanation. So, I ask the authors again for a revision of their manuscript prior to acceptance, as I am convinced, that incorporating the points below would further improve the ms.

 

Major comments with regard to content

The study area description, from my point of view, still can be improved. In my last review I asked the authors to provide more information about the elevational range and how the biomes present (i.e. Albany thicket, Grassland and Nama Karoo) are related to elevation. I recommended to add an overlay of contour lines to Figure 1 and/or Figure 2, or include a DEM as separate figure. Giving the highest and the lowest elevation within the study area, as done by the authors in the revised version, cannot substitute detailed three-dimensional elevation date for explaining spatial patterns of the occurrence of the major biomes Albany thicket, Grassland and Nama Karoo. Contour lines or a DEM are easily extracted from the SRTM data, so I ask the authors again to include this in the ms.

In the first round of review, I asked for climate charts. The authors now provide one single chart showing the monthly sums of precipitation but without noting to which biome this chart is related. I would like to see three different charets (in case those data are available) for the three biomes Albany thicket, Grassland and Nama Karoo, showing both monthly sums of precipitation and the mean temperatures.

In L127-129 the authors state: “The soil physical properties included organic matter content, sand, clay, coarse fragments, and silt, whereas the chemical properties nitrogen and organic carbon.” Where does this information come from? Is it sampled in the field or extracted from a database. Either provide some information about the sampling procedure or, in the latter case, provide a reference.

The important aspect of grazing for present-day vegetation structure, species composition and diversity patterns is still not touched (the same holds true for fire). I recommend to include this aspect at least shortly in the discussion section.

 

Minor remarks

L6t9-70: redundant, the following sentence says the same

L75: [16] chronology of references, this should read [13], please adjust

L80: Olea europea: is it native to South Africa, or is it planted/cultivate? Please explain

L87-88: redundant, the sentence above says the same

L105: transects instead of transacts (also L109)

L106: “Vegetation units the categories of other portions in...”: bad wording

L110: plots: above you state that you sampled transects: please clarify

Author Response

I have attached the comments to the your questions. Thank you so much for adding imput to my paper.

Author Response File: Author Response.pdf

Round 3

Reviewer 1 Report

I think the QGIS 2.18.0 is a GIS software, which you used to extract the climate and soil data, but not the climate and soil data soures.

Author Response

Thank you for your comments.

Author Response File: Author Response.pdf

Reviewer 2 Report

In the revised version of the manuscript entitled „Influence of environmental factors on the species richness and diversity in the semi-arid environment, South Africa” the authors reasonably addressed most of my concerns raised in the first rounds of review. However, I still have two points which must be corrected prior to acceptance for publication:

1) Figure 1 now has an overlay of contour lines, which is perfectly fine, the numbers however seems to be in tens of meters which must be noted in the Legend or in the figure caption.

2) In the climate chart, now the temperature is included. Conventionally, the annual course of mean monthly temperatures is presented as lines, while mean monthly sums of precipitation are presented as bars. I would like to ask the authors to modify the climate chart accordingly. In addition, please mark the location of the weather station in Figure 1 and/or Figure 2.

If these last changes are made, from my point of view the ms can be accepted for publication.

 

Author Response

Thank you for your comments.

Author Response File: Author Response.pdf

Round 4

Reviewer 2 Report

In the last round of review, I opted for “minor revision” with two particular points to be corrected:

1) Figure 1 now has an overlay of contour lines, which is perfectly fine, the numbers however seem to be in tens of meters which must be noted in the Legend or in the figure caption.

and

2) In the climate chart, now the temperature is included. Conventionally, the annual course of mean monthly temperatures is presented as lines, while mean monthly sums of precipitation are presented as bars. I would like to ask the authors to modify the climate chart. In addition, please mark the location of the weather station in Figure 1 and/or Figure 2.

The authors changed the figure caption of Figure 1, but I guess it is still wrong as the authors write “Location of the Mountain Zebra National Park (MZNP) in South Africa and the three biomes with contour lines in meters in the study area in the park.”  I believe it must read: “Location of the Mountain Zebra National Park (MZNP) in South Africa and the three biomes in the study area in the park with contour lines in tens of meters.” Please check and correct, if necessary, in the running text different elevations are presented than those in Figure 1 in meters.

In Figure 2 monthly mean temperatures are now presented as line, but as the scale of temperature and precipitation is different, both y-axes must be used, the left one for precipitation (in mm), the right one for temperature (in °C), a scale for temperature is currently totally missing.

In addition, I asked for marking the location of the weather station in Figure 1 or 2, this is also still missing.

So, once more, I ask the authors to make these corrections prior to an acceptance of the manuscript for publication.

 

 

Author Response

Response to the reviewers

Thank you for all your input. The response to all comments are below.

Reviewer comment 1 : Figure 1 now has an overlay of contour lines, which is perfectly fine, the numbers however seem to be in tens of meters which must be noted in the Legend or in the figure caption.

Response to comment 1: Thank you for this comment. The suggestion is now added on the Legend of Figure 1. The Legend now reads “Location of the Mountain Zebra National Park (MZNP) in South Africa and the three biomes in the study area in the park with contour lines in tens of meters.”

and

Reviewer comment 2:  In the climate chart, now the temperature is included. Conventionally, the annual course of mean monthly temperatures is presented as lines, while mean monthly sums of precipitation are presented as bars. I would like to ask the authors to modify the climate chart. In addition, please mark the location of the weather station in Figure 1 and/or Figure 2. In Figure 2 monthly mean temperatures are now presented as line, but as the scale of temperature and precipitation is different, both y-axes must be used, the left one for precipitation (in mm), the right one for temperature (in °C), a scale for temperature is currently totally missing.

 

Response to comment 2: Thanks for the accurate comment. The omission of units of measurement from the graph was a mistake. An updated graph has now been added so that the legend includes the units of measurement. We however strongly believe that a second vertical axis is unnecessary because the range of both variables (with the discrepancy in units acknowledged) overlaps. Thus, in its current form, the visual illustration is succinct, and we would like to appeal for it to be accepted with a single axis. The location of the climate station in the park has now been marked and thank you in figure 2.

Reviewer comment3: The authors changed the figure caption of Figure 1, but I guess it is still wrong as the authors write “Location of the Mountain Zebra National Park (MZNP) in South Africa and the three biomes with contour lines in meters in the study area in the park.”  I believe it must read: “Location of the Mountain Zebra National Park (MZNP) in South Africa and the three biomes in the study area in the park with contour lines in tens of meters.” Please check and correct, if necessary, in the running text different elevations are presented than those in Figure 1 in meters.

Response to comment 3:I have now changed the Legend of figure 1 and it now reads “Location of the Mountain Zebra National Park (MZNP) in South Africa and the three biomes in the study area in the park with contour lines in tens of meters.”

Reviewer comment4: In Figure 2 monthly mean temperatures are now presented as line, but as the scale of temperature and precipitation is different, both y-axes must be used, the left one for precipitation (in mm), the right one for temperature (in °C), a scale for temperature is currently totally missing.

Response to comment 4: With respect to the climate graph in Figure 2, the concern about double vertical axes that you raised was addressed in the response document. We had, for brevity, pleaded that the single axis be allowed to remain. This is because the range of both mean precipitation and temperature largely overlapped for our study. The discrepancy in the units of measurement has now been included in the legend of the said image. The legend would have been unnecessary if we opted for a pair of axes.  

Reviewer comment5: In addition, I asked for marking the location of the weather station in Figure 1 or 2, this is also still missing.  

Response to comment 5:The location of the climatic weather station is also labeled on the map and referred to in the text, which is now highlighted in red on page 5. I have updated my manuscript here with the highlighted corrections required.