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How Do Ground Litter and Canopy Regulate Surface Runoff?—A Paired-Plot Investigation after 80 Years of Broadleaf Forest Regeneration
Article
Peer-Review Record

River Buffer Effectiveness in Controlling Surface Runoff Based on Saturated Soil Hydraulic Conductivity

Water 2021, 13(17), 2383; https://doi.org/10.3390/w13172383
Reviewer 1: Janis Kreiselmeier
Reviewer 2: Anonymous
Water 2021, 13(17), 2383; https://doi.org/10.3390/w13172383
Received: 21 July 2021 / Revised: 20 August 2021 / Accepted: 26 August 2021 / Published: 30 August 2021

Round 1

Reviewer 1 Report

General comments

The authors present a very interesting study on how forest management affects soil hydraulic properties, and therefore, how maintaining a buffer of intact forest close to a stream may help reduce surface runoff and potentially soil erosion.

To determine the soil hydraulic conductivity, double ring infiltrometer measurements were done in different plots affected by forest management activities like selective logging, skidder tracks, cleared areas and pristine forest from 1 to 12 years after the last activity. Further, soil water retention was determined. This data was used to parametrize a 2D simulation of saturated water flow generating surface runoff at different management stages with different precipitation scenarios with and without a stream buffer.

The authors found that logging and line planting activities have significantly reduced the surface conductivity of the soil with rather long recovery periods of 10-15 years and up to 20 years in skidder tracks. Their simulations showed that this causes more surface runoff than undisturbed forest. A buffer strip close to a stream may alleviate these adverse effects.

This is a very relevant topic, not just in tropical areas since climate change may alter precipitation patterns all over the world, e.g. in some areas of Europe, with more intense rainfalls delivering huge amounts of water within a short time that cannot infiltrate causing devastating floods. The role of forest management in altering soil hydraulic properties and its effects on runoff deserves more attention in order to be able to take preventive measures.

Overall, this is a very nice study with interesting results. I congratulate the authors on their work. Nevertheless, the manuscript needs some revision, mostly regarding additional information on the sampling and modelling procedures as well as site information to be able to better evaluate the results.

The Materials and Methods section is a bit ambiguous and needs to be clarified. Only when reading the Results and Discussion section the experimental setup becomes clear since parts of the Methodology are placed here. This should be revised.

Also, the experimental setup is a bit shaky since only one infiltration measurement was done per plot, location and topography. This needs to be mentioned and discussed as a potential source of error since heterogeneities in the soil structure cannot be captured with this setup.

The model setup and the model itself need a more in-depth description. There is hardly any mention on how the model operates, not speaking of which model was used.

The Results and Discussion section presents mostly results, but does not discuss these results with respect to existing literature. If I am not mistaken, there is not a single reference to other studies in this section.

More information in the specific comments below. My overall recommendation would be between Accept after minor revision and Reconsider after major revision. Since I think more information is necessary to judge the results properly I chose major revision.

Specific comments

Abstract

[19]                       "The results founds showed"

Introduction

[35]                       "(Some studies"

[64-69]                 Are these the authors hypotheses or is there any literature the authors can refer to back up the statements in this paragraph? Either way it may be good to show some studies here investigated the recovery of soil hydraulic properties after disturbances.

[68-69]                 "is believed to be able to restore recovery the soil hydraulic properties"

Materials and Methods

[86]                       "is classified as Ultisoil (USDA soil taxonomy) and remains"

[85-89]                 Do the authors have more information on the properties of this soil such as texture and bulk density? If so, I think it would be helpful for the reader to provide such information. Since soil cores were taken, at least bulk density should be available.
What was the distance between plots and how did the authors ensure comparability among them?

[102ff]                  Just so I understand correctly: the experimental setup was a false chronosequence, correct? 11 plots at different stages of development all measured in the same year? Please clarify here to avoid confusion.

[106]                     11 plots * 4 locations * 3 repetitions = 132 infiltrometer tests, not 123.

[108-110]            "based on differences in topography" – Please clarify here that upper, middle and lower slope were sampled. This only becomes clear later on in the Results section.
Eventually, there is only one measurement per plot, location and topography? It should be mentioned that heterogeneity of the soil cannot be captured with this.

Figure 1               If available, could the authors please add an overview map showing all plots?

[117-118]            From the manuscript: "Saturated hydraulic conductivity (Ks) is a key property of the flowpaths of almost all modes of streamflow."
From Ziegler et al. (2004) which the authors cite here: "We focus on Ks because it is a key property in the activation of flowpaths in almost all modes of streamflow generation"

                               Please paraphrase in own words. Also, Ks is not a key property of flowpaths, but in the activation of them as written in Ziegler et al.

[116ff]                  Please provide more information on how the infiltration experiments were conducted (e.g. soil preparation, duration)

[123ff]                  "An additional 32 undisturbed…" New paragraph from here on.

[123]                     The 32 undisturbed soil samples were only taken from skidder tracks. Were they all taken from the surface? Figure 2 shows 26 retention curves. Two for each year from 0 to 12 years after. Please clarify.

[132-135]            Why was the Ks measured after the retention measurement at h=-500cm and not at the beginning when the sample was already saturated? Couldn`t this be an additional source for error in the determination of Ks when samples are used after dewatering and resaturation?

[159]                     Could the authors please provide more detailed information on the 2D flow model here. Since it is an important part of this study it should receive more than three short sentences in the Methodology section. All the model setups should be described here, not in the Results section.
Also, the determination of canopy cover should be explained here.

Results and Discussion

[173-177]            Here the bulk densities would be interesting to show compaction of the soil and to interpret these results. I agree, this is probably increased compaction at this site. With just two samples per development stage it is difficult to account for small scale heterogeneity. This should be acknowledged here.

[182-184]            The curve at 10-20 cm does not exhibit greater changes than the subsurface soil

[194-196]            How do they authors get to the number of 15 years? An estimate? Please clarify

[205-212]            Based on my own experiences I agree with those statements. But could the authors please provide references for it.

Figure 6:              Please explain the abbreviations in the figure.

[228-231]            This paragraph should be moved to the Methods section with more detailed information on how the canopy cover was measured.

Figure 7:              What do the authors mean by "The data were assumed to represent a logged area". Where canopy cover estimations done in a logged area? Please clarify.

[235-254]            Large parts of this paragraph belongs to the Methodology section in my opinion.

[252-254]            What parameters were used for the undisturbed layers at depths >15 cm?

Figure 9:              There is no reference to this figure in the text and also no explanation

[286ff]                  Where the runoff hydrographs created at the lowest point in the slope? Is there also aggregated information on the runoff created by the different management types? This could be a very interesting information.

Figure 12:            (a) and (b) should have the same range on the y-axis to better show the differences between SRO with and without a river buffer

[304]                     The abbreviations Qp and Ip were not introduced previously

[311-312]            "between the scenario….the coefficients of Qp and SRO are shown"

[314ff]                  What is the Qp coefficient? The ratio of Qp and peak rainfall?

Author Response

Please see the attachment

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments to the reviewed article are included in the attached file.

Comments for author File: Comments.pdf

Author Response

Please see the attachment

 

Thank you

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

General comments

The revision has significantly improved the manuscript. However, one of my main issues was not addressed in the response at all: the manuscript still lacks a discussion of the results with respect to other literature. The results need to be put into context. The authors should at least provide a good explanation as to why they chose not to add this. Without that, I cannot recommend to publish the otherwise good work.

 

Specific comments

The numbering in the minor comments below refers to the revised version of the manuscript:

[64]                        "and disturbances affected to soil hydraulic properties"

[90]                        "and 40% or more silty."

[128]                     "pounding depth"

[141]                     "is one of the propertyies"

[185]                     "Figure 10 shows"

[191]                     "interval depth, following the soil layers."

[198]                     "vegetation is measured"

[201]                     "were was established"

[235]                     "soil hydraulic conductivity estimated needs at least an estimated 15 years to recovery time and reach the levels of a virgin forest."

[252]                     I do not see how the referred study [12] supports the notion that field sampling is preferable to ex-situ methods since it only took soil core samples and is mostly about different fitting approaches. I suggest to look into the works of Reynolds et al. (2000; DOI 10.2136/sssaj2000.642478x) and Fodor et al. (2011; DOI 10.1016/j.geoderma.2011.07.004).

[266]                     "(P=prescipitation"

[291-301]            This paragraph should be moved to the Materials and Methods section together with Figure 10.

[296]                     "as is shown"

[297-298]            "..and -150 cm. Therefore, we used the soil layer between -60 and -100 cm to represent…"

Response 28      "Runoff hydrograph was created at the edge of the river channel as described in the

Figure 7."            In Figure 7 I cannot see where the runoff hydrograph is generated. Please add a short explanation in the text.

Author Response

Thank you very much for the opportunity in the journal.

We have revised the manuscript as the reviewer's recommendation.

Please see the submitted manuscript for your consideration.

Thank you very much

Author Response File: Author Response.pdf

Reviewer 2 Report

Line 137. Change the drawing number.
It should be Figure 1.

Author Response

Thank you very much for the opportunity in the journal.

We have revised the manuscript as the reviewer's recommendation.

Please see the submitted manuscript for your consideration.

Thank you very much

Author Response File: Author Response.pdf

Round 3

Reviewer 1 Report

The minor comments were addressed appropriatly by the authors. Nevertheless, I think the discussion had more potential. There still is hardly any reference to other literature and the authors unfortunatly did not reply to my comment on this topic. Or their comments got lost in the manuscript system?

 

Author Response

Thank you for the reviewer comments.

Please see the attachment for the detailed revision.

 

Author Response File: Author Response.pdf

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