The manuscript reviews bark beetle (BB) outbreaks in Czech Republic for the last 240 years. The authors collated much data of different quality on such BB gradations and related the damage wood to meteorological extreme events. While such gradations usually followed windstorms in the 19^th century, the recent and most devastating gradation was primarily related to warmer and drier weather prevailing during the last decade in the frame of climate change. Authors highlight the importance documentary databases with rich information on development of the environment and the socio-economy that foster the understanding of current forest damages.

I found the paper too long, the descriptions too detailed (though very interesting) and the conclusions too poor to be published as a concise paper. There are several ways to cope with this manuscript: to allow a long paper like this, or to improve the manuscript by reducing the information to digestible texts and figures, while putting details into the supplementary material. I propose the second treatment, by focusing on the following aspects:

Language: Much of the content can be improved an English brush-up and by more precise writing. I had much difficulties in the first half or the text and less so in the rest. Perhaps, the first part was not treated with the same care than the second part. Just my impression.

Descriptive event history on BB gradations: The information could be put in a chronologically ordered table, listing the most important triggers and forestry concepts of fighting against BB presence and also mentioning windthrow events.

Figures 7-10: Could be put into a supplementary material. Instead, one figure would do to show the length of the BB gradation (in lines) and the impact of windstorms on salvage felling. Here, the big impact of the 2018 storm Burglind could be highlighted, which presumably strongly amplified the BB gradation.

Windstorms: It is unclear to me why the authors claim that windstorms were only important in the 19^th century. Rather, by looking at figures 7–10, it appears that such storms (usually winter storms) had quite an important role as a trigger. But the information is simply missing, i.e. the exact date of the strongest winterstorms (compare e.g. Usbeck et al. 2010, Agric. For. Meteorol. 150).

Coniferous vs. deciduous tree species: I could not find information on the percentage of forests in CR that represent natural forest communities. I suspect that a high proportion of the coniferous forests are planted since perhaps 200 years. BB infestations could be seen as an interaction of non-natural forest trees, windthrow (mainly in wintertime when coniferous trees are more susceptible than deciduous trees) and warmer/dryer weather in the frame of climate change. The conclusion that “many spruce stands now appear to be located in unsuitable environmental conditions” could be highlighted and substantiated with more detail.

L28: «negative impacts» Impacts on what? On vegetation? On forests? On Nature?

L29: overpopulation: gradation?

L30: More specific here?  ...caused a catastrophic Norway spruce decline with xxx ha of spruce stands affected.

L31: Again, not very precise: Huge bark-beetle infestations followed extraordinary hot-dry episodes in summertime that reduced the vitality of Norway spruce...

L32: In addition, (not „on the other hand”)

L40-65: This can be reduced to few lines with the same information remaining.

L66: Here, it is better to start with "In the Czech forestry literature, ..." as this sentence now focusses on Czech republic.

L66-79: There is a long history of bark beetle impact in forest in the Czech Republic, with focal areas of investations (Sumava and others), with some exceptional years; this should be said at the end in order to change to the central part of this study: to contextualize the most recent calamity.

L81-83: Questions 1 and 2 could be reordered: first the question is about the context of the most recent calamity, and then the question would logically be whether the changing climate has altered the regimes.

L86: “analysis and discussion”

L86: …outbreaks. Results are discussed in the context of climate change.

L87-91: can be deleted.

L93: Follow normal paper structure: Intro, Data and methods, Results, Discussion, Conclusion

L94: Section 2.1 could be reduced by putting the data into a table.

L94: According to Wiki: Czech lands, not Czech Lands

L130: spatial? if yes: grid data or station data?

L146: replace “territorial” by “spatial”

L147: replace “for their detailed study” by “for detailed analyses”

L 154: replace the beginning of the sentence by “This reference was preferred over the more recent one of 1991-2020 because...“

L155: Whatever the intention (more stable or not), the older period was also cooler and more moist.

L153-164: It is difficult to follow how significance of the anomalies were indeed defined. Some more detail may be helpful.

L180ff: Sections 4.1.1 to 4.1.4 are boring to read and lack reduction. The information could be summarized and the text could go into supplementary material

L264-247: Text can be deleted here.

L267-419: I wonder whether it wouldn’t be possible to roughly quantify the bark beetle damage in the years before 1980. There is some information mentioned in the text. The text may be too detailed.

L452-454: Please clarify the sentence by putting the verb “appear” e.g. after “directions”.

L573-574: That’s exactly the reason for the huge bark beetle calamity: the interaction with windthrow. I bet that salvage logging after windthrow was also the highest ever in CR history. This should be discussed, too.

L600-605: This is a poor conclusion. Climate change is not the only reason why bark beetle outbreaks have increased. Rather, there is an interaction of long-term Norway spruce plantations, windthrow events and amplifying effects of warmer temperatures. I wonder to which extent CR would naturally be covered by Norway spruce and what would result as the plantation legacy of the past 200 years. To conclude would mean to promote more deciduous, stand-forming tree species to be planted in the future.

L940: A figure caption should be self-explaining. Here, a minimum of information on the calculation of the significance should be added.

L945: The period in the caption in unclear: according to the text, the data refers to four selected outbreaks in the 1980, 1990, 2000, and 2010s; this should be clarified. In addition: why are these outbreaks not addressed in detail? Are they really evenly distributed among the four decades?

Overall: I enjoyed reading this paper this interesting paper that uses a range of archival and instrumental data to better understand the inter-relationship between bark beetle outbreaks and climatic parameters, with considerable impact to the economy of such outbreaks. The wealth of materials that the authors have processed is commendable, with a large volume of materials reviewed and a complex picture starts to emerge. I think that there is considerable merit within the paper, but I do have some concerns with how the paper is currently presented, these are listed below, I also provide an annotated copy to support the authors in the revision process.

My key concern is that the paper presents a very detailed understanding of human-environment-climate interactions over several hundred years, with examples recognising these complex interactions, however the conclusion states that this is a function of climate change. Such a statement I feel fails to give justice to the complexity of the different aspects you so carefully detail in the paper. Climate change may have exacerbated the impacts, but I believe you demonstrate a much complex picture of interactions throughout the paper.

I think you need to present a chronology of windstorms within the paper, these appear important throughout the record, not just the historical period. This could be presented alongside the bark beetle outbreaks to help the reader see the relationship.

Key points that I believe should be addressed following revision:

This is a long paper with a great level of detail, whilst this is valuable and informative it does mean you need to ensure that key points are clearly detailed. I have suggested a couple of places where this could be more concise in the annotated version.

Lines 50-80, I think this needs to be more concise, it is not incorrect but not critical to the readers understanding.

155-157, I am uncomfortable with the way you are using the scPDSI, why not just present this as scPDSI-12?

470-480 I felt that you needed to explain the spatial and temporal changes in land management earlier, could you present changing extent of forestry in CR through a table or graph underneath Fig 1 or 2. I felt you also need to discuss the different forestry practices of the times, you recognise that extensive lowland forestry took place in the mid-20C but fail to then consider has the increase you attribute to climate change just been a function of these woods maturing. Also what impact does large monoculture conifer plantations have, compared to mixed conifer/deciduous?

480 Do we get different types of bark beetle, are they responsible for different outbreaks, do you need to try and distinguish between different beetle outbreaks and the different climates they preference, do we have different beetles impacting forests in the last 50 years?

545 A little more detail needed.

Discussion: You need to provide a more detailed analysis of the role of windstorms, these appear to be significant throughout the record, not just historically, this needs to be explored more fully.

Conclusions: I think the paper demonstrates a much more complex picture that cannot simply be brought down to the points presented here. Looking a the data I think you need to reflect on iii) as I do not see this clearly within the data. You provide a wealth of information in the paper detailing the complex interactions that may explain changing patterns of forestry, landuse patterns, management practices, beetle outbreaks and climatology, all of which contribute. To argue recent outbreaks are a function of climate change fails to acknowledge the evidence presented in the paper, that demonstrates an emerging complex picture, of which climate change may be exacerbating the incidences, which are a function of complex human-environment interactions.

Figure 1&2: It is crucial to present the windstorm data alongside this information. You present a strong argument for windthrow damage in the earlier period, but how does this coincide with the bark beetles, without a long chronology of such information it is difficult for the reader to discern what role this has, and whether it is diminished in significance in the last 50 years.

Figure 4-6: Why not present a scPDSI-12, -18 or -24, this would be better than a cumulative monthly (scPDSI-1?) anomaly of the scPDSI for the timescales presented. It would be helpful for the reader to see the bark beetle patterns of damage alongside the climatological information, add graph below scPDSI annual/summer anomaly.

Please see annotated paper for suggested minor modifications

Prof. Neil Macdonald, University of Liverpool