Counter-Intuitive Response to Water Limitation in a Southern European Provenance of Frangula alnus Mill. in a Common Garden Experiment

Round 1

Reviewer 1 Report

In the manuscript “Counter-intuitive response to water limitation in Frangula alnus Mill. provenances originating from different latitudes in Europe”, the authors present morphological and phenological data from a common garden experiment comparing individuals from three climates - Italy (hot), Belgium (intermediate) and Sweden (cool) - to answer questions related to their resilience to drought. Their results suggest that individuals from Italy (i.e. from the hottest region) were most susceptible to drought, contrary to their hypothesis and finding from many other researchers. Overall, this is a very well written manuscript and I applaud the authors for a very thorough description of the methods, statistical analyses, and results. As a result, apart from one major concern I have mostly minor comments.

 

My main concern is actually a quite fundamental one. Drought appears to be the main theme of the current version of this manuscript (lines 42-48 and others) and the authors set up the study based on the hypothesis that plants from southern regions are more resilient to drought – something that has been fairly well established for other species. Accordingly, the authors perform a drought experiment on genotypes originating from Italy, Belgium, and Sweden. However, according to lines 118-120, these three locations do not represent a clear gradient in precipitation. I understand that there is a clear gradient in temperature across these locations and I do not intend to invalidate the study or results presented – but the authors should restructure the introduction to emphasize temperature over drought like they did in the discussion (lines 536-538). At the very least, the authors need to discuss the link between drought and temperature. Another main point the authors make is that timing of precipitation is predicted to change, with longer droughts and stronger, more infrequent rainstorms. The drought treatment followed saturating the soils reflects prediction in the study design. However, how does this relate to the temperature gradient? Are there differences between the three sites compared here? Do you have any metrics of interannual variability of precipitation between the sites, or length of periods without precipitation? I hope this makes sense.

 

Minor comments:

29 – change “treated” to “droughted”

32 – change “advanced” to “delayed”

55 – change “intraspecific” to the odd, but grammatically more correct “intraspecifically” (or better, change it to “within species”)

160 – change “till” to “until”

198 – move “scored” before “two”

Figure 2 (and others) – add some indication of statistically different parameters (e.g. letters). Also arrange some of the panels so they do not take up so much room

391-402 – add percent changes here, which would make it much easier to interpret the effects of drought here

545-552 – this is a lot of restating of results and could be cut/shortened

573 – there is still a spell-check indicator here (“s” of “expectations”)

Author Response

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Author Response File: Author Response.docx

Reviewer 2 Report

Mijnsbrugge et al. have compared the response to withholding water of Frangula alnus plants originating from different latitudes in Europe. Overall, manuscript is interesting and contributes to the understanding of drought response mechanisms. The experiment is well designed, and the manuscript is concise and clear.

I only have a criticism regarding the number of replicates. It is not clear in my opinion how many plants have been used during the experiment. In materials and methods, authors reported: “From the plants in the field trial (8 from Italy, 17 from Belgium and 14 from Sweden; each plant corresponds to a different genotype), eight cuttings per plant (clones) were taken”. Of these 8 clones, if I have correctly understood, authors used 4 plants as control and 4 plants as treated (line 150: with a few exceptions, what does this sentence exactly mean?). After the water withholding treatment, authors reported that “58,4% of the treated plants survived (Italian provenance: 21,9%, Belgian provenance: 68,2% and Swedish provenance: 67,9%). Since the number of dead plants is so high and they were excluded from the models, I believe it is important to clarify the number of plants that have remained. If, as example, only one or two plants for each genotype are still alive the clone and genotype factors are not so informative (as also highlighted by the figure 8 where the plants with Italian provenance seem only 7). Also, the degrees of freedom are different between each statistical analysis, is the number of replicates always different? I recommend clarify this point also to reinforce the strength of results.

I have also some concerns about the calculation of relative weight loss of pots. The period of withholding water treatment is long for not taking into account the possible weight increases due to plant growth or the weight losses due to the fall of leaves. If authors have a percentage of weight variation caused by plant changes, this information might be inserted within the manuscript.

 

MINOR COMMENTS

The title is unappealing, I suggest modifying it.

There are too many figures, some of them should be merged.

Author Response

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Author Response File: Author Response.docx