Mesofauna at the Soil-Scree Interface in a Deep Karst Environment

Round 1

Reviewer 1 Report

This is a profound multi-dimensional study of the collembolan community at different altitudinal levels of a scree deposit covering the slope of a valley in the Slovak Karst National Park. Design and execution of the study are flawless, and so are processing, presentation and discussion of the data.

I have only reservations concerning the term “subtroglophile” when applied to Collembola. You adopt Sket’s definition: Species occurring in subterranean habitats perpetually or temporarily, intimately associated with the surface in some biological functions. I think it is hard to lay the finger on any biological function that forces a springtail to leave the “voluntarily” sought subterranean domicile. Sket’s concept fits paradigmatic species such as Troglophilus neglectus (perpetually) or Limonia nubeculosa (temporarily), but it hardly applies to, let’s say, Lepidocyrtus lignorum, because this species can probably satisfy all its demands in underground habitats. I feel that in several cases “weekly troglophile” would be the more appropriate expression, instead of subtroglophile. Granted, this a hair-splitting terminological dissent. It doesn’t affect your conclusions.

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Fine paper!

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Reviewer 2 Report

The work under review is a rather interesting study related to very subtle mechanisms of the functioning of collembola communities in peculiar mountain conditions. It seemed to me very thoughtful and well executed, although, in my opinion, the authors sometimes take wishful thinking when interpreting the results obtained, but this, of course, is a controversial issue. In general, the work can undoubtedly be published in the Diversity journal. All my remarks, comments and questions to the authors are given in the margins of the manuscript.

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Reviewer 3 Report

The authors of this work examined variation in species diversity, vertical distribution and structure of Collembolan communities at the soil-scree interface in a karst environment. The aim of this investigation was to assess importance of microclimatic and edaphic factors, and the function of these unique environments as potential climate refugia for psychrophilic (cold tolerant) microfauna. To achieve their goals the authors established traps at ten horizontal layers, and two climatically different sites of a deep karst valley (i.e., at the valley bottom and top). Then the traps were sampled (twice ?) to investigate differences among “a warm period” and “a cold period”.

I have no doubt about the soundness of that work concept. The execution of fieldwork and sampling also seems to be well planed and conducted (though some clarification is needed). Moreover, taking into account current environmental changes, I believe that results of that investigation provide valuable data that might be of interest for broader scientific audience and are, therefore, worth of publication. However, in my opinion, the manuscript still needs a lot of work before it can be considered for publication. With true regret, but I have to recommend rejection of that manuscript. Bellow, I have provided as detailed comments as possible, and I would encourage the authors to correct the manuscript and consider its new submission.

My specific comments and objections:

2. Materials and Methods.

Lines 114-115. “The studied scree slope … is located on the right side of the gorge”.

I do not think it is of any importance whether the slope is located on the right or left side, on the other hand considering microclimate the information on the slope exposition is crucial.

Lines 115-116. “Two sites along … scree slope were selected from the bottom of the valley to the upper part of the slope”.

Two sites do not form any transect, so they cannot be really located “along … slope” or “from the bottom … to upper part …”. They were just located one at the bottom and the other at the top of the slope. This information has to be rewritten.

Line 120. “ass. …”.

As a general rule each abbreviation should always be defined at its first usage. Meaning of that one might not be obvious for some readers. Since it is used only twice, I would suggest using the whole word without abbreviation.

Lines 121-125. For clarity, I would suggest to number the listed profile layers, i.e.:

“The scree profile compriced of three well-defined layers: (1) …, (2) …, and (3) …”

Lines 128-131. See my comment above.

Line 155. “Field sampling” or “Sample collection” reads better.

Lines 156-158. For clarity, I would suggest to number the listed periods i.e.:

“in two climatically different periods of the year: (1) a “warm” perion …, and (2) a “cold” period…”

By the way using the term “season” instead of “period” would probably be more appropriate.

Lines 156-160. But most importantly, the authors have to provide clear information when and how often the samples were collected; they should also explain on what grounds they determined the exact division of the sampling “periods” (seasons). From the information currently given here it is not clear if the samples were collected only twice (i.e., on “19-Oct 2018” and “15-Apr-2019”) or were collected several times during each of the sampling “periods” (seasons). Moreover, examining Figure 2, I am not convinced if “19-Oct” was the best time to separate “cold” and “worm period” (season).

If the samples were collected several times it would probably be better to analyzed the data separately for four different seasons, that is not only for “cold” and “worm” but also for two intermediate seasons (“spring” and “fall”). Such four seasons are clearly visible in microclimatic data from SA site (see Figure 2). Based on these microclimatic data I do not really understand why the authors selected October 19 as the seasons border line. In any case, the division of seasons should clearly be explained and justified in Methods, and probably at least briefly discussed in the section “Discussion” as this could have significantly influenced the research outcome.

Lines 164-165. “at ten horizontal levels (5, 15, 25, 35 up to 95 cm)”.

This information is confusing. If ten levels were sampled all should be listed (instead of five as it is done now), alternatively the upper and lowest can be listed with information on the interval between the consecutive levels.

Line 172. “according to [51]”

I believe that “according to Rusek [51]” is a proper citation format.

Line 184. “Tw/Tc, …”.

As a general rule each abbreviation should always be defined at its first usage. The meaning of Tw and Tc should clearly be defined here.

Lines 204-227. That is the whole section 2.5.

This whole section refers to the recorded species composition, diversity and abundance. Thus this section logically follows the last paragraph of the section 2.2. The other thing is, that these parameters should be clearly defined here before their usage in any other parts of the manuscript, with the exception of Introduction of course (see my detailed comments bellow). Moreover, at present, an earlier section (that is 2.4.) describes analyses done on collembolan species richness and activity, which means it uses terminology prior to defining that terminology. Therefore, I suggest providing the current section 2.5. directly below the section 2.2. Alternatively, the current section 2.4. together with the last paragraph of the section 2.5.2. can be combined and given at the very end of Materials and Methods as “Statistical analyses”.

Line 205. The format of that subtitle should be corrected.

Line 206. “Species richness (S total) and the number of specimens – activity (N total) of collembolan communities were evaluated… ”

Firstly, there are several different way the “species richness” is expressed in scientific literature, ranging from species number up to quite complicated indexes. I did manage to find out from the manuscript text in what way the authors measured “species richness”, but that should clearly be defined here without making the reader to guess that.

Secondly, remove the “word “activity” as it is a little confusing here. Moreover, “numbers of specimens” was recorded and this information should be clearly stated here. Then, since “numbers of specimens” was interpreted in terms of “Collembolan activity” explain clearly what “Average values” (see Line 208) “were used for … Collembolan activity”. Taking into account grammar, in the current form, that sentence refers to both “species richness” and “numbers of specimens” which, as I understand, is false information.

To sum up, this whole section (2.5.1.) should be rewritten, in such way that the terminology used here, and then throughout the whole manuscript, will be clearly defied here, this includes: “species richness”, “abundance”, “activity”, “cold-adapted (psychrophilic) species”.

Line 211. That (empty) line should be removed.

Line 212. “cold-adapted species”

For the terminology clarification I suggest the following: “cold-adapted (psychrophilic) species”. Moreover, I could not find anywhere in the manuscript clear information how the authors defined cold-adapted species. Does this follow some literature or the authors own classification? As I indicated above this should clearly be explained in the section Materials and Methods.

Line 217. “after [51]”

See my comment to the Line 172.

Line 214. “Selected ecological characteristics of the species were used according to literature sources (see Appendix A-B).”

References to literature on which ecological classification of species was determined should be given here, without forcing a reader to search for that to the Appendix.

3. Results.

This whole section needs very detailed correction and rewriting. Starting with its structure, which I believe should focus first of the most fundamental data, that is species composition, abundance and diversity and then their distribution and relationship to environmental variables. Alternatively, environmental data can be presented first (as it is done now) but analyses of the relationships between faunal data and environmental variables should rather follow a section with the faunistic data. Therefore, I would suggest moving the last paragraph of the section 3.1. As this paragraph focuses on correlation of the faunistic data with temperature it can probably be easily incorporated into the section 3.4.

The other problem is that most of Results are very descriptive and often repeat data already given in Tables and/or Figures, or lists data that can easily be given in Tables (often just incorporated into already existing Tables). This could considerable shortened that chapter and make it easier to read and summarize given data. Usage of jargon instead of precise terminology should also be avoided.

Some more detailed comments concerning Results:

Lines 230-231. “Different trends in the temperature regimes were observed at both sites, showing a markedly colder SA site compared to SB…”

This statement is false. It is clearly visible from Figure 3 that sites differ in temperatures, differed in temperature variability but temperature trends were generally quite similar (with positive correlation). I guess that this again is only vague and very relax terminology. But that is unacceptable in a scientific literature and has to be corrected.

Lines 233-234. “Tw SA +6.6°C ± 1.6 and SB +16.6°C ± 0.1; Tc SA +0.8°C ± 0.2 and SB +8.1°C ± 0.3; …”. Firstly, there is no point to provide the plus (+) sign before positive temperatures. Secondly, there are many measures of data dispersion, so the authors should clearly define what does the numbers that follow the ± sign mean (i.e., SD, SE, temperature range or some other dispersion measure). Finally, I am convinced that providing these data in a Table (they can easily be added to Table 1) would make them much easier to read and interpret, and the text would also read better.

Lines 240-242. “depth profiles of the scree showed more or less balanced temperature variation in the middle and deeper layers (35-95 cm), i.e., more stable temperature regimes”.

Trivial statement, I would be very surprised to see the opposite. There is really no point to repeat such trivial “discovery” twice in the same sentence. Moreover, while after examining Figure 2, I noticed that temperature variation at SA in winter season was indeed high compared to other data, it was still noticeable smaller in the upper layer compared to deeper layers. Guessing the authors intentions, the following would read better:

“As expected, middle and deeper layers (35-95 cm) showed considerably smaller temperature variation, however, at the site SA during the cold season the variation was relatively high across the whole depth profile.”

Line 247. “more or less balanced temperature means were recorded … at site SB in that period”

Firstly, what does “more or less balanced” mean? Less variable? Secondly, I see from Figure 2 that temperature variation in May (which seems the phrase “in that period” refers to) was higher at SB than at SA.

Line 247. “In June 2017, the soil moisture content…”

There is no really point to refer in Results to the exact time of moisture measurement. As a part of methodology this is given in Methods. Discussion of the method limitations (a single measurement) can be given in appropriate section of Discussion, but in Results reference to exact methodology is not really necessary and may even be confusing.

Lines 253-254. “where a slightly lower value of this parameter was observed”

The following is simpler and reads better: “where a noticeable lower pH value was measured”

The caption of Table 1.

“Microclimatic and soil-chemical characteristics (mean±SD) at two scree sites in …”

After providing in the Table caption the information that the given values represent means±SD there is no point to repeat that information so many times in the Table footnote (where at present it is repeated five times). In the last sentence of the footnote provide information to which letters this refers to. In general the following would read better: Significant differences between temperature values are indicated by letters (a,b). In Table these letters given as “superscript” would be easier noticeable. As I indicated above, I strongly suggest providing in that Table also all the values given in lines 233-235.

Lines 259-260. “at the sites”

“at both sites” reads better.

Lines 262-269. This paragraph analyses relationship of faunistic data with environmental variables. As I indicated above, I suggest to present faunistic data first.

Line 262. “The temperature negatively correlated with the species richness…”

While technically this statement is true, it sounds somehow awkward. Temperature is clearly independent variable and species richness dependent variable; no one would expect the opposite. Therefore, I strongly suggest reversing the variable orders in that statement.

Table 2.

Part of the line under “N_Collembola” is missing.

Lines 279-280. “Overall, higher activity (21,330 individuals) and species richness (50 species) were recorded at scree site near the valley bottom (SA) compared to the upper slop site (SB, with 10,825 individuals and 44 species.”

The authors should avoid unnecessary repetition of the same words and listing numbers that can be given in Tables (this is only one example of such completely unnecessary repetition). The following is considerably shorter, simpler and reads better:

 “Overall, higher species richness and activity were recorded at the lower (SA) compared to the upper site (SB).”

By the way, the term “individuals” sounds kind of awkward. I strongly suggest using “specimens” instead, these terms should be replaced throughout the whole manuscript. Similarly, instead of “at the two sites” (e.g., Line 273) “at both sites” reads better.

Lines 287-288. “At site SA, a more or less declining trend of Collembolla activity but an increasing trend of richness at depths of 45-85 cm were observed in the cold period (Fig 3).”

Firstly, such jargon as “more or less” should be avoided. But most importantly, after examining Figure 3 (B, the upper left one with SA/C data), it seems to me that both activity and richness show identical trend (decreasing between 45-95 cm) or kind of bimodal distribution (identical for both parameters), with peaks at 15-25 and 45-55 cm. By the way, Figure 3 is composted of four individual Figures, for clarity each should be numbered individually (e.g., as 3 A-D) and quoted in the text accordingly. The same refers to Figure 4.

Lines 295-296. “N. koseli and P. carpaticus”.

The whole names of genus names should be given here. As a general rule genus names can be abbreviated only when they follow a species from the same genus. This is particularly important when a few species has genus names starting with the same letter (which is the case here). Moreover at the first usage in a new chapter or even a new paragraph the whole genus name should always be used.

Lines 299-304. “The dominant species … had high activity along the entire … profile”.

As I understand, species activity is assessed based on abundance, which means that “dominant species” and a species with “high activity” mean exactly the same.

See also my comment above regarding abbreviation of genus names.

Line 303. What does “character of exclusivity” mean?

Lines 303 & 304. “the more abundant species”

more abundant than what? Did you mean the most abundant?

Lines 305-306. “Morulina verrucosa … was associated with the surface layer of site SA”

This species was found only at the surface layer of the SA site, but it was found there in very low numbers. Records of a very rare species are usually a result of a pure luck, and cannot really be interpret as a results of the species association with particular (micro-)environment. Therefore, the conclusion quoted above is completely unjustified.

Lines 311-315. These data are not really apparent from quoted Figure and Appendixes. I strongly suggest adding at the bottom of each Appendix rows presenting numbers of species belonging to each of ecological groups, as well as other groups (such as cold-tolerant and endemic species). This will make the presentation of results clear and allow shortening the text.

Lines 327. (the caption of Figure 3.).

What does “cold-adapted forms” refers to?

are “(cumulative) activity densities” and how they were calculated? I could not find anything on that in Methods.

Figure 4 and Lines 341-349.

What are “(cumulative) activity densities” and how they were calculated? I could not find anything on that in Methods.

Lines 357-410. Chapter 3.4.

Firstly, I do not understand on what grounds the authors based their interpretation of NMS ordinations. In particular, based on ordination from Figure 5A they distinguished two clusters, i.e. one composed of SA samples and the other formed by SB samples. This division is indeed clearly visible on the ordination diagram. Then, within each of these two clusters they distinguished two sub-clusters – comprising 5-45 and 55-95 cm layers in case of SA samples and 5-65 and 75-95 cm layers. However, this division is not supported by any cluster analyses. Moreover, some samples (e.g., SA25, SA35, SA45, SA55 & SA65) are grouped together so closely, that I cannot imagine on what grounds they were separated into different clusters. Contrary, the authors’ statements results of NMS ordination do not allow separation of samples into any sub-clusters. Instead, these samples seem to be lined up along the second (Y) axis and this axis seems to correspond with the depth (or temperature) gradient. On the other hand the first (X) axis separating SA and SB samples might correspond to temperature differences between the two sites. To investigate these relationships the authors should run direct gradient analyses with application of appropriate environmental data. As I have already indicated, any temped of clustering data beyond the two obvious clusters representing SA and SB site, without proper cluster analysis is purely speculative. This applies to data from both worm (Figure 5A) and cold (Figure 5B) seasons.

4. Discussion.

This chapter seems to be written better, however also requires some corrections and its complete evaluation is not really possible without prior correction of the previous chapter (i.e., Results).

Some of my concerns include that authors repeat some of the results here, which is completely unnecessary. For instance, Lines 425-430.

Similarly to previous sections, this sections is also not free of imprecise and vague terminology, For instance:

Line 438. “carbon content is an indicator of nutrients”.

This statement is not true. Carbon content is generally considered as an indicator of an organic matter, whereas nutrients are usually associated with N and/or mineral elements essential for the existence of biota. This terminology should not be confused.

 

To conclude, despite an excellent concept, and well planned and executed experiment the final outcome is a high disappointment for me. This work requires both re-analyses of data and very detailed correction of the manuscript, which in many parts should be completely rewritten. Therefore, with regret, I have to recommend rejection of that manuscript as in the current form it is not suitable for publication. However, I would encourage the authors to correct the manuscript, this is why I have tried to provide as detailed comments as possible, and consider its resubmission.

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Round 2

Reviewer 3 Report

The authors have corrected or provided reasonable justifications of their point of view. So, I believe that their manuscript can be accepted for publication. Still, I provided a few relatively minor suggestions (see below). However, I think that the manuscript may still require language correction; not very intensive but still thorough. I have found several phrases, or the whole sentences, which sound strange to me; usage of jargon or sentences in which punctuation seems to be lacking. However, I am not the native English speaker, and, therefore, I do not feel confident to provide detailed linguistic recommendations. This is not the role of a reviewer anyway.

 

Some more detailed recommendations:

Line 21. “a more or less declining trend…”. What does ‘more or less mean? As I have indicated in my previous review such jargon should be avoided.

Line 23. an transition zone -> a transition zone

Line 107. A value of 0.01 in seconds of geographic coordinates represents a distance of ca.30 cm (which means it provides accuracy ±15cm). While such a high precision of geographic coordinates might be appropriate for a site of a specific sample collection, there is really no point to provide such a high precision for the area of whole Reserve. Rounding coordinates to seconds (48°37'4"N & 20°49'56"E) will point to a location only 12.5m distant and will still provide peaty high precision (1" represent ca.31m).

Lines 302-304. “cold adopted species” also refers to Collembola, so for clarity I suggest the following: “Vertical distribution of Collembola and separately cold adapted species…”

And then adding “total” when defining N and S, that is: “N – total number of Collembola specimens” … “S – total number of Collembolan species”.

Lines 338-339. For clarity I suggest the following:

“The first and second axis explained … of the variance, for the cold and warm period respectively”.

Line 350. Remove the following:”species like”.

Line 353. Remove the following:”the species”.

Line 355. The following probably sounds better: “…, and several other species, such as …”.

Lines 377-388. This whole paragraph should be rewritten. It is completely unclear why temperature symbols are given after the names of taxa. For example: “Collembola species (Tc, Tc min)”, “L. lignorum (Tw, Tw min, Tw max, Tc, Tc min, Tc max)”. By the way provide the whole genus names for both species listed here.

Lines 395-396. Grammar of that sentence seems to me a bit strange.

Line 422:”soil nutrients”. Do you really mean “nutrients” or only “organic matter” or both? I do not know references quoted here, so just wanted to make sure that there is again no confusion with terminology. However, other parts of discussion suggest that this may refer to “organic matter”.

Line 452. Remove the following:”more or less”.

Lines 454-455. “several abundant cold-adopted and eutoglophile species showed a reverse trend, i.e. higher abundances in deeper layers, more than Collembola overall.”

From that sentence (its second part) I understand that abundance of cold-adopted and eutoglophile species was higher than the total Collembolan abundance. This obviously cannot be true.

Moreover, usage of the word “reverse” is probably not really correct in that context - ”showed an opposite trend” reads better.

Line 466. “showed more a reverse trend”

What does that suppose to mean? How a trend can be “more reversed”?

A trend can be the same (similar) or opposite (different).

Line 475: Remove the following:”more or less”.

Line 478: ”an opposite trend” is probably more appropriate than “a reverse trend”. The usage of “reverse” should probably be checked throughout the whole manuscript.

Line 498: “mass associations” –> “large numbers” is probably more appropriate.

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