Should we use meshes or solid tube shelters when planting in Mediterranean semiarid environments?

Tree shelters in Mediterranean environments have a two-sided effect. They not only protect seedlings from browsing but also ameliorate microclimatic conditions, improving post-planting survival and growth. However, the ecophysiological basis of these effects are poorly understood. A factorial experiment combining light transmissivity and shelter type (solid tube vs. mesh wall) was carried out to assess the impact of contrasting microclimatic characteristics on seedling performance and physiological stress levels of shelters in two Mediterranean shrubland species (Quercus coccifera and Rhamnus lycioides) planted in a semiarid site. Even though seedlings in solid tube shelters experienced higher temperature and were slightly more photoinhibited, they had higher predawn water potential and, in general, better survival and growth than in mesh wall shelters. However, these effects were species-specific, with Rh. lycioides more favoured by solid wall shelters than Q. coccifera. However, root growth cannot explain these interactions between species and shelter type on seedling survival. Since light transmission had a marginal effect compared with wall type, we proposed that the observed effects and interaction with species are not dependent on light intensity or temperature but on other microclimatic differences like air velocity or light quality and distribution. Further studies should assess the importance of these factors on post-planting growth and physiological stress levels, which can be critical for matching the correct tree shelters type for each species in plantations in semiarid environments.

Thank you very much for your email from April 19 concerning the review of the manuscript NEFO 17 00336 Should we use meshes or solid tube shelters when planting in Mediterranean semiarid environments?. We would like to thank the reviewers for their helpful comments, which we believe have improved the clarity and impact of the work. Virtually all the changes proposed by the reviewers have been incorporated in the new version. These changes are highlighted in red font in our revised manuscript, and references to previous or current manuscript position of the changes are presented to facilitate location and checking. Main changes consisted in presenting a different Figure 4 and correspondent post-hoc test in agreement with Reviewer#1 suggestion. Also minor changes in the text have been conducted accordingly. Please note that specific reviewer inquiries are in italics, and our responses are in bold.
---COMMENTS FOR THE AUTHOR: Editor-in-Chief: Thank you for submitting your manuscript, which has now been appraised by an Associate Editor and two expert reviewers. Your manuscript will be acceptable after minor revision based on Associate Editor and reviewer comments below. Please provide a covering letter detailing your specific changes in response to each point raised by the Associate Editor and reviewers. Your revision is due within 6 weeks. AE: The paper by Oliet et al. ) describe a solid study with interesting results. Although much used in practice, not much have been published concerning physiological responses of seedlings to various plant tube materials and designs. Therefore this manuscript is interesting for readers of New Forests and is worth publishing. Both reviewers are positive with some comments that should be adressed before publication.
Thanks a lot for the positive appraisal of the manuscript Reviewer #1: The paper studies the influence of two types of shelters (mesh/tube) differing in their light transmissivity on the responses of hardwood shrubby species (Rhamnus and kermes oak) planted in a semiarid environment (Central Spain). This topic is indeed of interest for forest and restoration operations in which the early development of seedlings in harsh conditions is a major issue. The authors have carried out a convincing field experiment; the methods used are well detailed and sound; the results are also clearly exposed. Besides, the paper is very well written and the authors have shown a deep knowledge of the literature on this topic. I also found that combining analysis of above-and belowground morphological traits with ecophysiological (predawn potential, fluorescence) and microclimatic measurements is original and shed light on the processes explaining the results obtained. In summary, I really enjoyed reading this paper.
Thanks a lot for your positive inputs! Despite the undoubted quality of the manuscript, I have relatively minor concerns about some points I would like the authors to consider First, I was not convinced that the authors have always used statistical post-hoc tests in appropriate manner. For instance in Figure 4, post-hoc tests have been made to compare the combined treatments species*shelter*light transmissivity but it is unclear if the interaction is significant or not. If not, please consider to show results in a different way (analyzing for instance the main effects only as in Fig 1 or interaction of the second order). Same remark for Table 4: the interaction Species*Shelter is only significant for root length (Table 3), so post-hoc tests are not appropriate when analyzing the influence of the treatments on the other variables. Please check this point in your different analyses and correct if necessary.
We agree with the reviewer about the appropriateness of using post-hoc test for species*shelter*light transmissivity combinations if this tird order interaction is not significant. We have followed the Reviewer's suggestions in Figure 4 by analyzing the second order interaction for height and diameter, including in this figure the degree of signification of the ANOVA test for each of them. We have reworded the result section accordingly (Lines 320 to 322 of revised version). With regard to Table 4, we have removed post-hocs letters for all variables except root length. New explanations are given at Table foot. Second, the duration of the study is somewhat low: 16 months only from February 2014 to June 2015. I acknowledge that the first summer is often of a primary importance for plant survival but it also corresponds to a transplanting shock. To what extent this latter consideration could have influenced your results? Can you add some additional comments on this?
We have added some comments in the Introduction to clarify this question (Lines 100 to 102 of revised version).
Lastly, I have not well understood the method about roots measurements: what do you mean exactly when you indicate that "protruding roots from the plug" were analysed (P5)? I suppose it corresponds to the term "new root" introduced later in the paper. Can you clarify this point? Some pictures (if available), showing for instance the types of shelter would be helpful for the reader I think.
We refer to the roots that emerge out of the plug. As they do not include new roots formed within the plug, we agree with the reviewer that "new root" can be confusing. Therefore, we have changed "new roots" for "protruding roots" along the text, and explained more the "protruding" issue by adding "out of the plug" (see line 210-211 of revised version). We do not believe that pictures showing the types of shelter can be too helpful, providing the description given in Mat and Methods are clear enough, as they include transmissivity levels, colors, dimensions of the shelters and net holes dimensions.
Specific remarks P1L50 benifited = favoured ? Done P2L0 leporidae= rabbits and hare? It is easier to understand for the reader Changed to rabbits and hares P2L39-51 I particularly appreciated the good analysis of the literature! Thanks! P5 Were the protector stabilized by any particular system during the planation? Were there buried in the soil to assure stabilization? Yes, the protector was stabilized with a stake and buried in the soil. We Figure 4A in the following line. We have split Figure 4 in A and B P8L12 See remark above about root, this parameter "new root length" should be more clearly explained in the M&M section Done. See response to this comment above. P8L33 Microclimatic conditions more favourable (T, VPD) inside mesh shelters during… Added T and VPD in the sentence P8L43-44 Yes, it's difficult to interpret small differences with fluorescence P9L4-5 "restricted air movment…reduces foliar water loss and improved hydric water status" Yes, one could have expected a higher RH value inside tubes than inside mesh but this was not observed P18L54 "among levels of factor" is not very clear. Indicate that letters show significant differences between the type of proctor x and among the transmissivity levels Done as suggeted P15 0.081 not in bold Done, thanks for the thoroughly review. P20 remove "aa" for solid tube 80% Done P21 Fig 4a) heigh and 4b) diameter Done Reviewer #2: The work by Oliet et al. was aimed at improving the knowledge of the ecophysiological mechanisms occurring in plants growing in tree-shelter after transplanting in arid environments. They compared the effect of two types of shelterplastic tube and mesh-in combination with three different gradients of light transmissivity on seedlings of two species usually planted in arid environments for restoration purposes (Quercus coccifera and Rhamnus lycoides). Despite in international literature the studies on the effect of tree-shelter on early seedling development are pretty spread, most of them are focused on describing the shelter effect against browsing and/or on survival and seedling early morphology. Few experiments are designed to understand the ecophysiological basis to explain such findings. This is the strength point of this study, which was planned and carried out accurately. I enjoyed reading the manuscript by Oliet et al; all sections of the manuscript are well written, materials and methods are correct, and results are interesting and properly presented and discussed. Thus, my recommendation is to accept the manuscript. Just check citations in the text vs reference list (e.g. in page 2 Dupraz andBergez 1999 andMariotti et al. 2015 are cited but not present in reference list). Thanks a lot for your comments. We have incorporated mentioned references in the list. photoinhibited, they had higher predawn water potential and, in general, better survival 23 and growth than in mesh wall shelters. However, these effects were species-specific, 24 with Rh. lycioides more favoured by solid wall shelters than Q. coccifera. However, 25 root growth cannot explain these interactions between species and shelter type on 26 seedling survival. Since light transmission had a marginal effect compared with wall 27 type, we proposed that the observed effects and interaction with species are not 28 dependent on light intensity or temperature but on other microclimatic differences like 29 air velocity or light quality and distribution. Further studies should assess the 30 importance of these factors on post-planting growth and physiological stress levels, 31 which can be critical for matching the correct tree shelters type for each species in 32 plantations in semiarid environments.

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Physiological response to shelters (maximum photochemical efficiency and water 270 potential) and microclimate in summer.

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The small changes observed here might only reflect slight differences in this 359 deactivation but with no impact on plant capacity to survive and grow.