Aquatic Biological Diversity Responses to Flood Disturbance and Forest Management in Small, Forested Watersheds

Round 1

Reviewer 1 Report

The manuscript investigated response of macroinvertebrates to flood disturbance as well as forest management practices in small watersheds in US. The authors reported consistent nature in the macroinvertebrate composition across different types of storm intensities. The study concluded combined effects of flood and previous logging constrains habitat complexity. In general, the paper is well-written, the results are explained well with proper discussion and easy to flow. I only have a few comments that I would like the authors to consider to improve the manuscript, after which it may be considered for publication in Water.

 

• The authors collected a very interesting dataset covering multi-faceted aspects of river morphology, hydrology, however the water quality aspects are relatively unexplored. I wonder how the changes in the flood has impacted the water quality parameters and if that has anything to explain the recovery of benthic macroinvertebrates. Some recent literature indicates that to explain the variation in the community structure of benthic macroinvertebrates, flooding impacted water quality changes are indeed significant (Effect of a summer flood on benthic macroinvertebrates in a medium-sized temperate lowland river by Chattopadhyay et al 2021, Effects of floods on macroinvertebrate communities in the Zarin Gol River of northern Iran: implications for water quality monitoring and biological assessment by Gholizadeh, 2021).
• I suggest restructuring the introduction portion (especially last two paragraphs) a bit. It would be better if the authors lay out clearly the research gap and put out the hypothesis more clearly.
• It would be nice to know about the severity of this flood event. Is the information about the return period available?
• Along with the richness measures, were any diversity index such as Shannon’s index considered?
• In these type of studies, it gets challenging to distinguish effects of floods from the phenological processes. Specifically, in northern hemisphere June and July are months associated with peak emergence of invertebrates. I would like to see some discussion if there was any effect of phenology in the abundance and richness they observed.
• Minor comment :but please double check the font sizes are consistent, i.e suddenly the font size 592 and 593 are different, there are many such instances occurring in the paper.
• Please improve the quality of figures 1 and 9 if possible in the next iteration.

Author Response

See comments, sincere thanks for your review.

Author Response File: Author Response.pdf

Reviewer 2 Report

Manuscript 1342996 Reviewer Report

“Aquatic biological diversity responses to flood disturbance and forest management in small, forested watersheds” by Robert J. Danehy, Robert E. Bilby, Tiffany E. Justice, Gary T. Lester, Jay E. Jones, Sogal S. Haddadi, and Glenn A. Merritt

General comments:

The article concerns the important topic of the response of aquatic ecosystems to flood disturbance gradients. It is well written, and the methods, including the data analyses, are appropriate and thorough.

Specific comments/suggestions:

1. The literature review would seem to provide a reasonable basis for hypotheses regarding the response of the ecosystems to a gradient in flood disturbance. At present, the Introduction ends with a series of questions. It would be easier for the reader to follow the Discussion if these questions were replaced with hypotheses. The principal research question is already captured in the opening paragraph of the Introduction: “We are interested in how disturbance severity influences degree of system alteration and rates of recovery as processes adjust to new conditions [in headwater catchments that have been altered by forest management for wood production].”

There are two manuscripts that may be worth including in the literature review, albeit concerning a lowland river:

Le, C. T., Paul, W. L., Gawne, B., & Suter, P. J. (2020). Quantitative Flow‐Ecology Relationships Using Distributed Lag Nonlinear Models: Large Floods in the Murray River Could Have Delayed Effects on Aquatic Macroinvertebrates Lasting More Than Three Decades. Water Resources Research, 56(8), e2019WR025896.

Le, C. T., Paul, W. L., Gawne, B., & Suter, P. J. (2021). Insight into the multi-decadal effects of floods on aquatic macroinvertebrate community structure in the Murray River using distributed lag nonlinear models and counterfactual analysis. Science of The Total Environment, 757, 143988.

These articles describe patterns very similar to those reported in your manuscript, including the delayed effect of a large flood, differences in the dyanimic response of richness and abundance to a large flood, changes in community composition, and a possible connection to woody debris.

2. The disturbance categories are confounded with elevation, as you have noted. There is already a mention of confounding with the adiabatic temperaure lapse rate, as a result, but it might be confounded with mean basin slope as well. Is there anything else with which we should be concerned? This is a limitation that perhaps warrants further mention in the Discussion.
   
   The GLMMs have been used to describe differences among disturbance categories and times, but it could be worthwhile including the watershed characteristics or abiotic variables as covariates in the macroinvertabrate GLMMs (%EPT, %Chironomids, %Scrapers, Abundance, etc.) to account for potential confounders, minimise noise (to reduce the widths of confidence intervals), and (importantly) explain the observed differences. It would be worthwhile mentioning, as well, how you checked that the model was appropriate for the data (e.g., residual diagnostics).
3. When was the last large flood event prior to the 1997 sampling occasion? This relates to the position of the ecosystem in the recovery from flood disturbance. That is, how well does it represent the status of the community prior to the 2007 event?
4. Line 625. Should that be “effect?”
5. It would be worthwhile including the DOI for all references.

Author Response

See comments, sincere thanks for your review.

Author Response File: Author Response.pdf