the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Pioneer biocrust communities prevent soil erosion in temperate forests after disturbances
- 1Soil Science and Geomorphology, Department of Geosciences, University of Tübingen, Rümelinstr. 19-23, 72070 Tübingen, Germany
- 2Nees-Institute for Biodiversity of Plants, University of Bonn, Meckenheimer Allee 170, 53115 Bonn, Germany
- 1Soil Science and Geomorphology, Department of Geosciences, University of Tübingen, Rümelinstr. 19-23, 72070 Tübingen, Germany
- 2Nees-Institute for Biodiversity of Plants, University of Bonn, Meckenheimer Allee 170, 53115 Bonn, Germany
Abstract. Soil erosion continues to be one of the most serious environmental problems of our time, which is exacerbated by progressive climate change. Until now, forests have been considered an ideal erosion control in this regard. However, even minor disturbances of the forest floor for example from heavy vehicle used for timber harvesting can cause substantial sediment transport. An important countermeasure is the quick restoration of the uncovered soil surface by vegetation. In this context, biological soil crusts (biocrusts) can play a vital role, as they are known for their soil-protective effect. This study examined the natural succession of pioneer vegetation in skid trails on four soil substrates in a central European temperate forest and investigated their influence on surface runoff and sediment discharge. We applied rainfall simulation experiments on small-scale runoff plots and continuously surveyed vegetation during the same period, primarily to map biocrust development.
Skid trails on clayey substrates showed considerably higher biocrust cover and species richness. Biocrust cover was higher in center tracks than in wheel tracks, while there was no clear difference for biocrust species richness with regard to track position. Although biocrusts were quickly overtopped by vascular plants, they managed to coexist until their growth was restricted due to leaf litter fall. Brachythecium rutabulum and Oxyrrhynchium hians were the most important and persistent pioneer biocrust species, while Dicranella schreberiana and Pohlia lutescens were volatile and quickly disappeared after spreading in summer. Soil erosion was reduced with pioneer biocrust vegetation in summer, and again increased in winter. Total amount of sediment discharge was clearly site-dependent, indicating a high relevance of underlying substrates. Sediment discharge was 13.2 times higher in wheel tracks compared to undisturbed forest soil, and bare soil runoff plots produced 22-fold sediment discharge compared to undisturbed forest soil. Overall, bryophyte-dominated biocrusts contributed more to mitigating soil erosion than vascular plants. When soil coverage exceeded 50 %, biocrusts resulted in an average of 18 times less sediment loss compared to vascular plants.
Corinna Gall et al.
Status: final response (author comments only)
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CC1: 'Comment on bg-2021-343', Georgios Kazanidis, 09 Feb 2022
Comment on the under-review manuscript “Pioneer biocrust communities prevent soil erosion in temperate forests after disturbances” by:
Attapun Anivat*, Bella O'Hara*, Emily Tanner*, Ilja Belovolovs*, Laura Barraclough*, Georgios Kazanidis**
*Undergraduate student in the course “Critical Thinking in Ecological and Environmental Sciences” at the University of Edinburgh
**Tutor in in the course “Critical Thinking in Ecological and Environmental Sciences” at the University of Edinburgh
Dear authors,
as part of the undergraduate course “Critical Thinking in Ecological and Environmental Sciences” at the University of Edinburgh we have read carefully the mentioned above manuscript and we would like to express here our thoughts. We have found this piece of work is, in overall, a timely and interesting manuscript and we hope that our thoughts will help the authors to improve the status of their under-review paper.
Overall Summary
This is a very interesting topic. The study is, in overall, well organized and executed. The manuscript is also in good order and there is clear presentation of results and appropriate use of English language. The ‘Introduction’ could be shorter with less detail; it should focus to attract more the interest of readers why this research must be done, and what are they key knowledge gaps that it addresses. Occasionally there is too technical terminology used which makes understanding challenging for the non-experts (see detailed comments below). It seems that some major gaps exist in terms of statistical analysis and how the authors have examined the role of environmental parameters in shaping the floral communities. There should be better use of references in ‘Materials and Methods’ and better elaboration in parts of the ‘Discussion (e.g., in parts of Section 3.1 - see detailed comments below). A final major point is that the authors really need to highlight the key findings of their study – currently it seems that their major finding about the superior role of biocrust communities in preventing erosion is already mentioned in the literature. The innovative aspects of the study need to be made clear early in the manuscript and in the ‘Abstract’.
Abstract
In overall it is well written. We suggest the authors make clearer why is it important to study what they have studied e.g. why is the succession so important? In addition, the final 2-3 sentences of the ‘Abstract’ need some modifications – making them simpler and easier to understand will increase their impact. It might be preferable to avoid use of “we” in the abstract and perhaps the detail of results could be reduced; authors might also be more clear in highlighting one main conclusion to express.
Introduction
Line 35: Please provide some examples why soil erosion will increase through climate change. Also are there any (numerical) projections about how much erosion will increase in years and decades to come?
Line 41-42: Is there a reason behind these relatively large shifts in erosion of forestlands?
Line 44: Please use more plain language in “showed that unsealed forest roads at the catchment scale” so that the reader can get a clearer understanding.
Lines 46-53: This numerical information provided is useful, but we feel it would be better to be used in the “Discussion”. Here in the “Introduction” make sure you present the bigger picture and why it is important for this research to be carried out. Lots of numerical information can distract the readers from the major messages.
The sentence on line 55 could be modified to summarise the point of referencing all of these studies and then group them together in the citation for reference
Line 61: Please explain where the term “cryptogamic” refers to. Also, what do you mean by “understory”?
Line 63: Perhaps replace “edaphic” by “floor”?
Line 68: We feel this should be “bryophyte-dominated”?
Lines 68-70: Please provide briefly some information on the direction of these effects by bryophytes e.g. increase/decrease in runoff etc.
Line 81: Please improve wording.
Line 86: The authors need to make clearer which is the research gap and especially to link it better with previous lines/sections.
Lines 92-94. It is welcome that authors make clear the objectives of their study. We feel though that it would be even better if they make some null hypotheses related to their points e.g., how do they expect that the underlying substrate, vegetation cover and track position will affect soil erosion?
Line 96: Please explain what you mean by “interrill”.
In the “Introduction” and especially towards the end of it the authors should make some clearer references on how their findings can be used in good practices for management. They can elaborate on that aspect in the Discussion.
Materials and Methods
Line 121 and further: Could abbreviate genus name in species scientific names for conciseness purposes (e.g. P. sylvestris)
Lines 140-146: Please provide references about the use of similar experimental set up in previous studies.
Lines 148-149: The authors need to provide more information about the particular selection of this rainfall intensity e.g., is similar intensities observed often in the studied area? Provide also relevant references.
Line 149- 153: The authors should provide more details about technical aspects mention in there e.g., measurements on surface run off. Please also provide references.
Line 154-155: For how long were the samples left to dry?
Line 156: Please mention what is exactly the aggregate size and which are the measurement units for this parameter.
Line 159-162: It is interesting that measurements on elements (C, N) were made. Please make sure that there are the relevant references made in the “Introduction” so the sections of the manuscript align better.
Line 173. Please improve the wording about nomenclature in Tables.
Lines 183-187. It seems that post-hoc tests were not carried out. Also, it seems that the role of environmental parameters in the flora structure / development has not been accounted/examined for. If this is the case, then it is regarded as a major gap and needs to be addressed.
More information on the number of replicates is needed.
A map showing where the research was carried out would be welcome.
Overall, we believe that the “Materials and Methods” section could have been written more succinctly to make it easier to read.
Results and Discussion
Line 191: ‘Section 3.1.1 – Biocrust species composition’. It seems that this title is not fully adequate as in the section 3.1.1 there are also results about temporal trends. This should be reflected in the Section 3.1.1 title.
Line 193: Please avoid using where possible abbreviations (e.g., ‘UF’) as it is difficult for the reader to follow them.
Line 196: Please clarify what is ‘protonema’.
Line 205 / Table 1: Could table 1 provide more information on composition, cover and richness? Do we need Author column?
Lines 222-223: This is just an assumption on the role of pH; there should be appropriate statistical analysis to explore the role of abiotic environmental parameters in shaping the communities.
Tables 1 and 2: The information shown here is interesting; however it seems that these Tables are a bit long – how about moving them to Supplementary Material?
Lines 227-230: These are major findings and should be moved earlier/up in the Results and Discussion section.
Lines 232: Please clarify the categories that the species belong to e.g. do they belong to ‘protonema’ or another category?
Line 234: “little importance”: Please provide numbers rather than terms like “little importance”.
Lines 227-242: This is a big chunk of results but discussion on them is absent.
Line 243: It would be better to start the section with the key result; discussion on it should follow.
Line 246: Please see comments above about stats regarding the role of environmental parameters.
Figure 1: Could be useful to have included a longer caption describing what photographs demonstrate to make the article more accessible for the readers that do preliminary paper skimming. A map of the area would have been highly beneficial for the readers to better visualise the studied site spatial distribution.
Line 271: It is not clear what the authors try to say here e.g. that there are similar trends between biocrust and total coverage trends? Or something else? Please clarify.
Figure 2 caption: Perhaps it would read better as “mean values and standard error are given”. Please also remind to the readers the number of replicates.
Line 282: The values of pH should be mentioned.
Lines 288-289: The authors should elaborate on their statements about contradictions between their findings and those from (Corbin and Thiet, 2020; Bergamini et al., 2001; Fojcik et al., 2019).
Lines 289-292: The authors should elaborate on the mechanisms driving positive correlations between vascular plants and moss growth.
Line 292: The statements/discussion on biocrust should be on a separate paragraph.
Lines 327 – 338: Please make sure that you provide p-values where needed. Also, it is not necessary to use extensively phrases such as “A was X times higher than B”. Providing the average values, standard error and the p-values would suffice.
Lines 339-341: See our comments above about examining the role of environmental parameters in shaping discharge / run off. For example, how much of the variability in discharge is explained by differences in the soil features?
Sections 3.2.1 and 3.2.2 should be merged. The independent and response variables should be subject to appropriate statistical analysis e.g. distance-based linear modelling (Clarke and Gorley 2015)
Clarke KR, Gorley RN (2015) PRIMER v7: User Manual/Tutorial PRIMER-E: Plymouth
Lines 398-401: Some of the lines mentioned here should had been included in the Materials and Methods. Also it is not clear where the term ‘reduction’ refers to – please clarify.
Figure 5: The box plots for biocrusts and vascular plants are very close (this is not necessarily bad) and some of the outliers for biocrusts may be regarded as outliers for vascular plants (and vice versa). It would be helpful to see the outliers for each of them with different colours. We feel that a sudden change in the colour scheme on this graph could confuse the readers that got used to seeing dark green as ‘wheel track’ and light green as ‘central track’ in previous 3 figures.
Line 425 Conclusions
Line 426 : it seems that null hypotheses were not made; it is suggested to adjust accordingly the text at the end of the “Introduction”.
The conclusions section looks too lengthy; it should appear more succinct and with higher impact. Focus on your key findings and how they fill gaps in the literature. Avoid repeating results and numerical values.
Could include more discussion of direction and opportunities for future studies
Lines 450- 456: Would it be also of interest to study the factors that support higher growth rates for the biocrust communities?
Appendix
Figure A1. Please clarify in the image (using arrows) the wheel track and center track.
It seems that there is some inconsistency in editing/coloring of symbols across the figures e.g., see color code used Figures 3 and 4.
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AC1: 'Reply on CC1', Corinna Gall, 10 Feb 2022
Dear students and tutor of the course “Critical Thinking in Ecological and Environmental Sciences” at the University of Edinburgh,
thank you very much for taking the time to revise this preprint and for giving this positive evaluation with constructive comments. We were very pleased to see that our manuscript is an interesting topic for your course, and we appreciate your valuable suggestions for improving our manuscript. We will consider your comments and respond in detail soon.
Best regards,
Corinna Gall
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CC2: 'Reply on AC1', Georgios Kazanidis, 10 Feb 2022
Dear Corinna Gall,
Thank you for your kind reply.
Dr Georgios Kazanidis,
University of Edinburgh
- AC3: 'Reply on CC2', Corinna Gall, 12 Apr 2022
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CC2: 'Reply on AC1', Georgios Kazanidis, 10 Feb 2022
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AC1: 'Reply on CC1', Corinna Gall, 10 Feb 2022
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RC1: 'Comment on bg-2021-343', Bettina Weber, 14 Mar 2022
Review of Pioneer biocrust communities prevent soil erosion in temperate forests after disturbances
by Corinna Gall, Martin Nebel, Dietmar Quandt, Thomas Scholten, and Steffen Seitz
The study of Gall and coauthors covers a very interesting and largely neglected topic, i.e. the role of cryptogams (and mainly bryophytes) in erosion prevention after disturbance by logging in temperate forests. The study was carefully designed, conducted on several different soil types and measurements were made several times after the disturbance had taken place. Thus, I think the study definitely should be published after the following suggestions have been considered.
First, I doubt that many of the bryophytes reported in this study fully meet the characteristics of biological soil crusts (biocrusts). The biocrust definition, as it was first brought forward by Belnap, Büdel and Lange (2003) in the first Ecological Studies volume on biocrusts, referred to communities of organisms that live within or only few centimeters on top of soil. A key characteristic is that the major part of the biomass is located within the soil and that it creates a hardened soil surface (an encrustation). I think both of these factors are not fully met by the communities reported here. In genera like Atrichum, Rhytidiadelphus and Plagiomnium the major part of the biomass grows above the soil surface and I also have not experienced a soil hardening effect in the vicinity of them. Thus, I think the term “biological soil crust” is irritating in this context, as the reader expects somewhat different properties. I think that biocrusts indeed could occur at the slopes next to a forest path with species like Polytrichum piliferum and it might be that in some parts of the investigated sites biocrust fragments could occur. But for the complete community I doubt the correctness of this term.
However, I do not see that as a deficit of this study at all. The authors could describe the studied communities as bryophyte or cryptogam communities and they could discuss the similarities and differences between biocrusts and their study objects. I think it also is relevant that not only biocrusts, but cryptogam communities in general are highly relevant for a variety of functional ecosystem processes and the present study shows this clearly once more.
Second, I think the illustrations in this manuscript could be improved. In section 3.1.1 the composition of bryophytes is explained, but the taxa are only listed in a table and the taxonomic composition is not graphically displayed. I think this is urgently needed and would clearly improve the comprehensibility of the results. In figures 2 and 3 the line diagram is not the correct way to illustrate the results, as there are no data available for the times between the measurements. For this type of data, box-whisker plots are correct, as they have also been used in the subsequent figures. In figure 3, the signatures are difficult to be separated from each other; I think this could be improved regarding form and color. In all plots where sampling was conducted at different times, the statistics should be added in order to illustrate which changes were statistically significant.
Third, the naming of the plots could be improved. The names of the different forests do not mean anything to the reader. I think it would be better to name the plots e.g. according to the parent material, soil type and/or texture or to just give them numbers. This would be particularly helpful, as you explain later that the substrate indeed had an effect on the observed vegetation.
Fourth, I think it might be irritating to name only the month of sampling. It would be clearer if you name them e.g. as Mar19, Jul19, Oct19, Feb20
Fifth and finally, the language needs to be carefully and thoroughly checked throughout the manuscript. Beyond minor mistakes, which are not a big issue, there are also sentences where the meaning remains unclear. Thus, careful and thorough language editing is urgently needed before final publication could be considered.
These language problems cause problems like the following one:
In line 143-145 it is written that “Four ROPs were placed in the WT and the CT in every skid trail (n = 32), and two ROPs in the undisturbed forest soil (UF) next to every skid trial site (n = 8).” This is not clear. Does it mean that on every skid trail four ROPs were installed? This would mean that there were 4 skid trails in total? Does it mean 4 skid trails each at WT and CT? This needs to be clarified. Also the rainfall simulation numbers given in the following sentence are not clear. I think a thorough language check will help to also clarify these issues.
Besides that, I observed the following minor issues:
Line 35-37: In this sentence there are several language style problems. I would suggest to reformulate it in the following way: The most prominent soil loss occurs in agricultural environments, and thus a considerable part of relevant research is conducted in these habitats.
Line 46-47: here I think you want to say “The most important reason for this is soil compaction and reduced infiltration rates caused by heavy machines used for timber harvesting”
Line 48: significantly
Line 55: exchange “which” by “that”
Line 60: “These” instead of “those”
Line 75: As most studies investigating the impact…
Line 80-81: This sentence is upside down. ‘Pioneer biocrust communities could provide benefits’ or ‘the soil benefits from biocrusts’
Line 114: The skid trails show no geological formation, but the underlying rocks and soil do. Please adapt wording
Line 119: formed by extensive periglacial processes…
Line 125-127: There are several abbreviations that need to be explained: Ad-hoc-Ag Boden, Iuss Working Group Wrb, WRB Tool
Line 148: A rainfall intensity of 45 mm does not make sense. I think you speak of a rainfall intensity of 90 mm h-1, applied over a duration of 30 minutes
Line 200-201: meaning of sentence unclear
…and many more not listed here.
Bettina Weber
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AC2: 'Reply on RC1', Corinna Gall, 18 Mar 2022
We thank the reviewer very much for this in depth and positive evaluation of our work. Comments provide a strong basis for substantial improvements, which will be included after the review reports are complete.
Illustrations will be added as we strongly agree that adequate graphical display is most beneficial for this topic. Furthermore, naming and dating issues will be adapted as suggested. Moreover, a thorough language check will be conducted after revision of all given comments.
Lastly, we would like to thank the reviewer for the significant comment on the classification of plant communities as biocrusts. This hits a most interesting point that has been discussed intensively.
It is agreed that the moss genera mentioned in the review grow with the bulk of their biomass above the ground and do not meet the basic definition of a biocrust. At the same time, however, they make up a smaller part of the biomass at the beginning of succession. Along with many other moss species, single lichens, algae, and cyanobacteria, larger amounts of moss protonema can be observed on the soil surface immediately after disturbance. Together, they can show crustal characteristics at the beginning, which fulfill the definition of Belnap, Büdel, Lange, 2003. In this temperate forest ecosystem, however, they are found, as the reviewer is correctly assuming, only selectively and they continue to develop quickly, with the crustal characteristic disappearing more and more.
Nevertheless, this observation has been made more often, and very clearly e.g. in highly disturbed subtropical forest plantations, where larger crustal patches were still detectable after 2-3 years (Seitz et al. 2017, in this journal).
In this context, this early soil cover after timber harvest fulfills an essential (biocrust) function, namely, the protection against erosion at a moment when the soil is highly susceptible. This protective function then passes smoothly into further vegetation development and, according to our observations, is even more enhanced by fully developed mosses. However, the distinction between biocrust and cryptogamous or just non-vascular vegetation is not always easy to make.
In summary, we agree that the prominent use of the term biocrusts in the introduction and title may lead the reader down the wrong track. This will be adjusted accordingly, and more reference to cryptogamous and/or non-vascular vegetation will be made. Nevertheless, we think that plant communities under the biocrust definition are not yet adequately described in these mesic (and thus rather atypical) ecosystems. We therefore strongly welcome the reviewers suggestion to compare and discuss similarities and differences between the communities.
Corinna Gall et al.
- AC4: 'Reply on RC1', Corinna Gall, 12 May 2022
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AC2: 'Reply on RC1', Corinna Gall, 18 Mar 2022
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RC2: 'Comment on bg-2021-343', Anonymous Referee #2, 12 Apr 2022
The study by Gall et al. tackles a very interesting topic about biocrust formation in skid trails and their influence on soil erosion. Overall, the manuscript is well written and the topic well presented. The measurements are numerous and have been done during different seasons and vegetation stages as well as on different soil types and parent material. The article is worth publishing, however, it could be improved in my opinion with some of these suggestions.
In general, I think that the figures could be improved, especially Figures 2, 3, 5.
Figure 2 and 3 For Figure 2 and 3 I would recommend not using line charts but possibly box plots. Since these are specific monitoring times and not continuous monitoring it gives the wrong suggestion to the reader, especially since the slope of the lines is very different (because the x-axis distances are all the same, although timewise they are not, June-July is not the same time as July-October).
Figure 2 Perhaps you could consider, for Figure 2, putting the difference between wheel track and center track in one panel (bryophytes) and the difference between wheel track and center track for total vegetation in another panel. With an adjusted y-axis for bryophytes it would be much easier to see differences between the two track types. This is just a suggestion.
Figure 2 and 3 To distinguish the information in Figure 2 from Figure 3 it might be better to use different colours. In Fig. 2 bryophytes are presented in dark green while total vegetation is yellowish, in Fig. 3 these colours are used to distinguish the track types which makes it more difficult to grasp the information from the figure directly. Consider using larger symbols for bryophytes etc. so it is more easily readable.
Figure 5 The distribution of sample dots in Figure 5 just seems random and does not improve the quality of the figure. The information about the number of sampling points could also be added into the figure caption.
Line 148 rainfall intensity should be given as mm h-1. Do you mean 45 mm in 30 minutes meaning 90 mm h-1. This would be an extremely heavy precipitation event and one not typically found in the region, I presume.
Chapter 3.2.1 I understand that you want to distinguish the skid trails from the undisturbed forest, yet the results seem to show that wheel tracks and center tracks are very different in their soil erosion characteristics, maybe separate them when speaking about the total values for sediment discharge and surface runoff.
Lines 358-364 You speak of rainfall events, but you mean rainfall simulations? As I understand it, these ROPs can also be used to measure sediment loss and surface runoff during natural rainfall events, did you measure these in between your monitoring times?
Figure 5 As you write the higher the percentage of vascular plant cover or biocrust cover the lower sediment loss. Why is the sediment discharge for 11-25 % biocrust cover so low in comparison to the sediment discharge with higher biocrust cover (26-50%)? Do you think it is because of only few measurements were performed in this cover class? You should also explain not only the outlier dots but also your „sample“ dots in the figure caption.
Figure A1 Unfortunately, the rainfall simulator (except for the cannot be seen, consider using a different, more expressive picture.
Chapter 2.1 Consider adding an extra figure for the study area
Lines 27- 28 the last sentence needs work: … biocrusts showed an average sediment loss that was 18 times lower than under vascular plants.
Line 41 important dimensions?
Line 68 bryophyte-dominated biocrusts
Line 75 very most? As the most studies
Line 127 „a“ Eutric Cambisol
Line 135 „a“ Eutric Calcaric
Line 173 Nomenclature see Table 1 and Table 2 à please use full sentences or use brackets
Line 202 no italics for citation
Table 1 no italics for the authors
Line 313 further disturbance was detrimental
Line 349 rose again
Line 352 a difference by a factor of 5.7
Lines 356-357 keep value and unit together, 59 %
Line 375 skid trail
Line 407 with an 18-fold difference
Line 417 both scouring water? Maybe remove both
Lines 437-438 The pH was identified as the main influencing…
- AC5: 'Reply on RC2', Corinna Gall, 12 May 2022
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RC3: 'Comment on bg-2021-343', Anonymous Referee #3, 25 Apr 2022
This is an interesting study examining the importance of biocrust species on soil erosion. The experiments were conducted in an appropriate manner. Unfortunately, it is difficult to understand the contents, especially in the results and discussion section. Detailed information and key messages are mixed. A solution would be that the section is divided into the results section and the discussion section.
L109 “newly-established”: When were these skid trails established? Winter 2018/19?
L118 “a loess plateau”: I cannot catch the meaning.
L347 “bare soil ROPs”: The meaning is unclear.
Fig.2: I have not understood how to obtain the biocrust coverage. Did the authors remove plants except biocrust before taking photographs for biocrust?
Fig.3: Why did not data of vascular plants shown in October and February? I guess the difference between the total and biocrust in Fig.2 came from vascular plants; the differences were not zero in October and February.
Fig.5: Do the dots with gray color indicate?
- AC6: 'Reply on RC3', Corinna Gall, 12 May 2022
Corinna Gall et al.
Corinna Gall et al.
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