INTRO: Asbeck et al. studied the effect of various forest characteristics on the abundance and richness of microhabitats in living trees that are recognized as important structural elements for forest biodiversity. They also explored the potential of these forest variables to predict certain microhabitat types. They found that the abundance of microhabitats was significantly higher in plots located in landscapes with high forest cover than in landscapes with less forest cover. Additionally, the abundance and richness of microhabitats was positively dependent on tree diameter at the plot level. Highest microhabitat abundances were found in monospecific coniferous forests, whereas the greatest microhabitat richness was found in mixed-coniferous-broadleaved forests. Forest cover at landscape scale, forest type, number of snags, and average tree diameter at the plot level predicted the abundances of 12 out of 64 microhabitat structures.
MERITS: The study design is really extensive and impressive, including a huge number of trees, study plots and different microhabitat types. All studied variables are introduced clearly, and I really like that they are being listed in the abstract. Testing for the potential of the studied environmental variables to predict certain microhabitat types gives a practical application for biodiversity conservation and management. I also liked that you explained which statistical analyses you used, and communicated the results clearly. It was also good to stress that the analyses were done at the plot level. All in all, a really nice and clear abstract.
CRITIQUE: You mentioned that you included the influence of forest management in your variables. Were the study plots located in both managed and natural forest stands (in what ratio), or how was the effect of forest management addressed? I suggest adding this detail in your abstract. Additionally, could you have added some conclusions and something about the possible applications for conservation to the end of the abstract?
DISCUSSION: Including 64 different microhabitat characteristics sounds relatively ambitious. Could the results be more feasible and applicable from the biodiversity conservation and management point of view if there would be less microhabitat types? Or maybe it would be possible to group these microhabitat types under different categories? This could possibly make the results easier to perceive.
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INTRO: The aim of the study is to identify the key factors which drive local abundance and richness of tree related microhabitats in managed forest. Results highlighted that both local and landscape factors improve the density and diversity of microhabitats.
MERITS: This study contains very interesting and relevant quantitative findings for understanding the distribution of old-growth attributes in managed forest, which remains poorly known to date. These information provide importants improvements for management and thus for conservation of saproxylic species. Moreover, the study is based on field data has resulted in large and complete microhabitats dataset (64 types of microhabitats were inventoried).
CRITIQUE: Some methodological elements could be added (although it is difficult to give a lot of details in a short abstract):
- "forest cover in surrounding landscape": At what spatial scale did you measure this variable ? Is it measured in a buffer around each sampling plot?
- Is "tree dimensions" refers to DBH ?
- Some "main types" of microhabitats could be explicitly presented (e.g. cavities, fruiting bodies of fungi ...) in order to be more meaningful for readers unfamiliar with old-growth forest attributes.
DISCUSSION: The results of this study should provide practical information for forest management in order to enhance old growth attributes and thus associated saproxylic biodiversity.
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INTRO: The manuscript addresses the important question of biodiversity proxies for management: the authors ask how well can the pool of tree microhabitats (a proxy itself) be predicted by even more general proxies (landscape and stand characteristics). A broad conclusion has not been drawn but, to me, the fact that only 12 our of 64 microhabitat structures could be to some (unspecified) extent be predicted does not sound encouraging. Rather, this study encourages monitoring of tree microhabitats or their biodiversity directly.
MERITS: The study is based on a solid sample of stands and, as far as can be judged from the abstract, adequate statistical analysis. The only question regarding the latter is whether these were truly predictive models or were they explanatory models?
CRITIQUE: The main problem is a broad one: how much do such analyses depend on the particular list of microhabitats compiled (subjectively by human observers)? For example, reporting both the abundance or diversity of the microhabitats directly depends on the list. I therefore suggest some sensitivity analysis and separate reporting of individual crucial microhabitat types instead of pooling. It is a problem analogous to species assemblage analyses where the conservation concern may not be adequately described by species richness or diversity indices. A small issue with the abstract is that I would like to see a summarizing conclusion. And a technical thing worth mentioning: how many tree species were represented in the sample and were they all native? Please also confirm that the stands were naturally developed (and their age range), otherwise it would be important to reflect on (and analyse) their management history separately.
DISCUSSION: The manuscript describes an important field study. It is possible that the material is too heterogeneous for the simple summary given (forest types, ages, management histories etc.), and a promising path might be to pay specific attention on how particular tree microhabitats actually develop in the trees/forests studied.
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INTRO: This study explores the effect and predictive potential of variables ranging from landscape quality to tree specific characteristics on the abundance and richness of microhabitats that can be found from living trees. They found positive effect of forest cover and tree diameter on the microhabitat abundance, diameter also having positive relationship with microhabitat richness. For different forest types the effect depended on the type. The predictive potential of the different variables was found to be quite poor.
MERITS: Interesting study. Abstract has good language and it is logically structured. I think the motivation, methods and results are in nice balance.
CRITIQUE: Some minor problems with the writing.
Conclusions are missing.
DISCUSSION: I would love to get an idea what is the most important message in your opinion from your results. What does it mean that some variables had significant effect and some did not, given the introduction you provide for the topic? What do you conclude about the predictive potential of variables?
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INTRO: This study tries to predict the abundance and richness of microhabitats on living trees at a plot scale, using information about forest cover in the landscape, forest management and type, amount of snags and average tree diameter. It shows that the forest cover at landscape scale increase the abundance of microhabitats and increased tree diameter at a plot scale increases both the abundance and richness of microhabitats.
MERITS: They have used a large dataset of 2838 trees spread over 139 plots (each 1 ha in size), which should give a good dataset for robust statistics. Including both landscape scale variables such as forest cover and plot based variables such as number of snags, as well as measures about management, should make it possible to capture different aspects that potentially influence the microhabitats available.
CRITIQUE: It is a bit unclear to me what variables are included in the categorization of microhabitats, it would have been interesting to get some examples to have an idea about what the authors define as a microhabitat. I also think it could have been valuable to include other variables not connected to trees in the models, if the microhabitats are assumed to also reflect e.g. humidity. I miss some kind of concluding remark regarding how the results can be interpreted and used in a wider context.
DISCUSSION: This could have interesting implications if it is possible to replicate in other contexts that the exact forest of this study. However, I do believe that inclusion of additional variables would make that more possible. Although I understand what a high diversity of microhabitats is and why that is important, I do have trouble with understanding what a high abundance of microhabitat really is. Shouldn't that be extremely correlated to the surface area of the trees? As all parts of the tree surface is some kind of microhabitat. And thus, the result that a higher average tree diameter gives higher abundance of microhabitat is almost self-evident?