In this study the authors exposed the deadwood of different tree species with (1) different sun exposure and (2) in different diameter classes, to evaluate which combination is best suited to promote a high diversity of saproxylic organisms. Considering the timber price of each tree species the authors are able to calculate the most effective way of enriching deadwood for conservation purposes with this experiment.
This study makes an important contribution to the assessment of the success of nature conservation measures. Deadwood enrichment is one of the most important measures for the protection of forest biodiversity, but can be costly. Thus, it is of particular importance to scientifically evaluate the effectiveness of the measures. To disentangle the effects that determine the biodiversity in deadwood, experiments are the most accurate approach, especially with the combination of different aspects that determine the biodiversity in deadwood (tree species, sun exposure and diameter) as applied here.
I do not see any weaknesses in this manuscript.
In my opinion this research is very relevant to make qualified recommendations concerning deadwood enrichment in forests. So far, this experiment covers only the effects of fresh deadwood which is important for biodiversity but harbors only a certain proportion of saproxylic biodiversity. Therefore, it would be important to continue this experiment to see whether the relationship between biodiversity and the exposed deadwood changes with increasing age and decay of the wood. A change in this relationship, e.g. due to a fast decay of certain tree species that decreases the long-term positive effect on biodiversity, could also change recommendations made to people that apply deadwood enrichment.
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The manuscript "Fostering deadwood enrichment in managed forests - the importance of tree species and sun exposure for saproxylic species" by S. Vogel et al. tries to combine experimental assessment of the biodiversity of deadwood dwelling organisms with the economic value of the timber needed for their development. The experiment involved several tree species, in two dimension classes and three sun-shade treetments. Such interdisciplinary approach is very valuable as most of European forests are managed and the economy plays an important role for their owners.
The manuscript is based on well designed experiment allowing assesment of the importance of tree species and deadwood localisation in the forest for deadwood dependent organisms. Another very important merit is assesment of the economic value of wood, which needs to be left in the forest for conservation of forets biodiversity. Combination of these two aims together in one work is unique and may play an important role in convincing forest managers to leave some amounts of wood (different species and different dimensions) in the ecosystem.
There are some weaknesses of the manuscript, which needs to be solved. First is lack of any results and conclusions. There is an extensive description of methods applied and analyses carried out but nothing on the results. In effect, it is not possible to assess the real importance (impact) of the proposed piece of work. The second problem is that authors compared two different types of wood (logs vs. branches) to conclude on the influence of deadwood dimensions on biodiversity of saproxylic species. I'm not convinced that such approach is acceptable for two resons. The characteristics of these two types of deadwood are very different (proportion of late wood vs. early wood, proportion of easy accessible food, e.g. sugars). And in my opinion conclusion on influence of wood dimensions on anything can be formulated if there are several size classes involved in the experiment. In this case I would limit the conclusions to differences between stem and twigs.
The results (if shown) could be of high importance and will influnce the approach of forest managers to deadwood. On one side our knowledge about importance of tree species, environmental conditions and type of deadwood for biodiversity of saproxylic species is still very limited. On the other side forest managers (especially of forests outside of protected areas) have always dilemma how much deadwood and of what characteristic they should leave in the stands to sustain the forest biodiversity at certain levels. These two problem are properly addressed in the paper. Therefore, the paper is of high importance for nature conservation and for forest management.