|(Line numbers based on the author response version with tracked changes: bg-2018-521-author_response-version3.pdf)|
Thank you for once again reviewing your manuscript and for seriously and effectively addressing my concerns. I think that you have now solved the main problem in the previous versions, the plausibility of the water content values. I think that the calibration method and the orders of magnitude of the results now make sense, and I am really pleased about this. Of course it still does not imply that they necessarily present the correct absolute values, but together with the other microclimatic data they do show nicely how the dynamics of the water contents in these bryophytes may respond to environmental conditions. I think this is an important contribution of this paper.
Now that the main issue is solved, I think the manuscript just needs one more round of polishing, highlighting and discussing the exciting findings more, correcting some mistakes, optimising some graphs and formulations and checking for style and grammar.
The WC values now look more plausible to me and in the examples shown (Figs 2 and S6) they show a wonderful reaction to rain events. Could you corroborate this impression by a correlation between the WC and the rain amount in the preceding 12 h (or something like that)? It is interesting that the WC of the samples as 23 m sometimes do (especially on 10-09-2016) and sometimes do not at all (March 2015) react to rain. Apart from possible umbrella effects of the canopy, could it also be due to a reinstallation and recalibration of the sensors around June 2015? There seems to be a large and systematic difference between the EC (and WC) values before and after this maintenance period for the sensors at 1.5 m (Fig S5). I guess this may be partly due to the drier season after this period, but I am not convinced that this explains the pattern completely. It may be worth elaborating a bit on this point.
The diel fluctuations (mentioned P17, L1) in WC are not mentioned clearly enough in the results. They can be seen a little bit in Fig S8 and better in S5c, but the former figure is referred to only in the context of condensation and the latter not at all in results or discussion. I think these daily fluctuations deserve more attention (especially as you use it as a main conclusion), so I would discuss them with reference to figure S5c, or add another figure similar to Fig S8 but showing more days (only on days without much rain so that the scale of the WC can be precise enough to show the fluctuations - these are hard to see in Fig 2 and S6). I like Figure S9, but it does not show whether reaching the dew point is related to the fluctuations in the WC. An interesting analysis would be to calculate a correlation between the distance below the dew point reached and the response in WC on that morning. The same could be done for the fog events. The difference in daily fluctuations between the seasons (mentioned in the conclusions) is also interesting and worth some more discussion (P15 L2-3: is this phenomenon more frequent in the dry season?). In fact, I think this point could perhaps make for an additional publication by itself!
I think Figure S5 is useful, but I recommend making the graphs larger. In the supplement I do not think that there is the need to save space, so I would go for clarity here. I also like the magnification shown in S5c, though judging from the rain amounts it does not really correspond to the box in the coarse-scale graph, which I would recommend stretching vertically to make clear that the entire graph (all parameters) are shown in the magnification.
The way in which stemflow is discussed could be improved. In my view, this is not ´additional´ water in the sense that moisture input from condensation may be (so I would not merge these two points into one sentence like you now do, P16 L 30), but it is redistributed rain water (mostly, as condensation and fog would hardly lead to stemflow) that benefits epiphytes on the tree stem (i.e. in your case those at 1.5 m in particular). As stemflow concentrates rainfall from a larger area to the stem, this could explain why the bryophytes on the stem respond so reliably to rainfall. For a recent review about this see Mendieta-Leiva, G., P. Porada and M.Y. Bader, 2020. Interactions of epiphytes with precipitation partitioning. In: Precipitation partitioning by vegetation. A global synthesis, J. T. Van Stan IIE. Gutmann and J. Friesen, (Eds.). Springer Nature Switzerland: pp: 133-145.
And I think I found one important mistake in your calculation of activity times, or possibly two (sorry I did not notice this in the previous round):
1. You assume that “For the net photosynthesis (NP) it is required that … T > TCP”. However, the TCP is an upper limit, so for a positive NP you need T to be below this compensation point!
2. The range for Topt can be considered a range within (not above or below!) which NP is optimal. Therefore I would expect only one value for the % of time where the bryophytes at a particular height in the tree are within this range, not a range of %. This is in contrast to the other ranges which are ranges of estimates for which we do not know which applies so that indeed it is useful to report on the estimated % of time if we assume one or the other value.
Small typos / grammar problems (not exhaustively reviewed) and needs for short clarifications:
P3 L31 …communities were conducted …
P4 L25: add the tree species and some information about tis phenology (it seems from the discussion that it is a semideciduous tree..?). This is quite relevant for extrapolating the results.
P5 L12: 26-m-high
P5 29: data that could be used…
P5 L33: The electrical conductivity (EC) values on which the WC calculations were based (see Paragraph 2.3 below) showed some unexplained oscillation, causing …
P6 L9: please explain this ´fluctuated´
P7 L17: I would add here that 0% was an approximation (simplification), as no moss would really reach 0% unless in a good drying oven… But they would dry to a minimum WC of a few %, so near enough to 0% for this model assumption.
P8 L24: Please start this point by explaining why you calculated this (to estimate the likelihood of water input by dew?). It also would not hurt to introduce this idea in the introduction. I think it is a very important and exciting point!
P9 L7: Fig S5 does not show PAR values…
P13 L8: remove in before 90%
P13 L10: relatively similar or similarly high
P16 L7: those at 23 m
P16 L23 remove the second ´during the dry season´
P17 L8: we observed (instead of ´observed by us´)
P17 L14-16: stating that Leucobryum may have a low water retention seems strange, as this genus has special water-retaining cells… I would think that it is not particularly good at capturing water (e.g. from fog), but then very good at retaining it.
P17: I would consider removing L5-32, as it does not really add much to your story. The life-from discussion seems too much discussion for the amount of data you have per life form and does not sound like you have profoundly researched it yet. Similarly, with the number of samples you studied it seems unjustified to draw any conclusions about the pattern of distributions among height zones. You could mention this in the methods section where you present the species studied, to justify your choice by showing that you chose typical species for the ecosystem.
P22 L 1: I would not say that the WC has “turned out to be” the key parameter controlling the overall physiological activity of the organisms, because you did not measure this activity. Better use a more cautious formulation like “appears to be”
P22 L3 remove the comma after major rain events
P22 L8: here also remove the speculative remark about thallus morphology. This is, by the way, not a seasonal feature anyway…
P22 L13-14: do you really know whether this nightly condensation activates physiological processes? Is it enough for photosynthesis, for example? I do not think that we know this, and I do think it would be very important to know it, so perhaps formulate it as a research need rather than a finding.
Table 1b: please help the reader by providing the number of days for which the fog sensor was operational (in addition to the sensor outage times)
Table 3: please make clearer what data were used: the averages of the different samples per height zone? Or the individual samples (i.e. is the range shown a function only of the range of possible parameter values for the cardinal points, or also a function of the differences between samples?).
Fig 4 caption: I do not think that the ´Estimated´ is appropriate here.
Figure S8 caption: Exemplary