Linking Sap Flow and Trunk Diameter Measurements to Assess Water Dynamics of Touriga-Nacional Grapevines Trained in Cordon and Guyot Systems

Round 1

Reviewer 1 Report

The paper dealing with water dynamics in grapevines growing under two different training systems start with a good design of the trial, is well written and the results are quite interesting for the viticulture in general and the Douro area in particular. There is only one thing missing or I did not catch: you worked within a commercial vineyard planted in 2011 during the year 2017. You set "similar number of buds" but you did not mention at all the grape in your paper. Did you check the number of bunches on the two systems? Did you leave the same number of bunches in Cordon and Guyot? I believe this variable could affect water trends and you should have taken it into account on your research.      

Author Response

The paper dealing with water dynamics in grapevines growing under two different training systems start with a good design of the trial, is well written and the results are quite interesting for the viticulture in general and the Douro area in particular. There is only one thing missing or I did not catch: you worked within a commercial vineyard planted in 2011 during the year 2017. You set "similar number of buds" but you did not mention at all the grape in your paper. Did you check the number of bunches on the two systems? Did you leave the same number of bunches in Cordon and Guyot? I believe this variable could affect water trends and you should have taken it into account on your research.

We are thankful for the reviewer’s comments and careful reading of the manuscript.

Reply: Yes, the number of bunches were checked. No significant differences were found between the training systems. Yield components are been planned for being part of a separate paper. Thus, additional information was added as follows:

Lines: 387-388: “Nonetheless, no significant differences in cluster number and yield were found between training systems in our study (data not shown).”

Author Response File: Author Response.docx

Reviewer 2 Report

The title is appropriate and indicates the main message of the paper

The abstract is an accurate reflection of the full manuscript; abstracts mimic the structure of the paper, with succinct sentences each describing introduction and/or purpose, methods, results, and a concluding statement.

The introduction provides a detailed insight into the context for this paper and  is not excessively wordy. In the introduction paragraph is succinctly review the current literature. The study objectives are clearly and explicitly defined.

The Methods section provides an explanation of how and why a study was done to evaluate the daily and seasonal water dynamics in grapevines trained in the Guyot and Cordon systems throughout the growing season.

The methods are clearly described and justified, easy reproducible; sampling method, measures and instruments are clearly defined and justified.

Results and data are clear presented. All presented results relevant to the purpose of the research. Tables and figures are linked to key results and provide additional meaning to the written results.

Results are reported with an appropriate statistical support.

Discussion paragraph provide the context in which results are important. Connections are made to the broader literature, including what was cited in the Introduction.

All tables and figures are clear and add value to the text and highlight key aspects and they do not duplicate data elsewhere.

 The discussion detailed the importance of the results and defined the ‘‘place’’ the outcomes have in the knowledge economy.

There are recommendations made for further work and direction.

The conclusions are reflective and supported by the findings presented in the manuscript.

Daily thermal variability had an effect on trunk diameters, the leaf area index (LAI), daily and seasonal water dynamics in grapevines?

Were foliar or soil fertilizers applied during the experiment, with the possibility of influencing the results?

Line 78  - crops (e.g., in tomato plants [30], lemon trees [31,32], peach trees [33,34], and olive trees [35,36]. – keep the same font size

Comments for author File: Comments.pdf

Author Response

The title is appropriate and indicates the main message of the paper

The abstract is an accurate reflection of the full manuscript; abstracts mimic the structure of the paper, with succinct sentences each describing introduction and/or purpose, methods, results, and a concluding statement.

The introduction provides a detailed insight into the context for this paper and is not excessively wordy. In the introduction paragraph is succinctly review the current literature. The study objectives are clearly and explicitly defined.

The Methods section provides an explanation of how and why a study was done to evaluate the daily and seasonal water dynamics in grapevines trained in the Guyot and Cordon systems throughout the growing season.

The methods are clearly described and justified, easy reproducible; sampling method, measures and instruments are clearly defined and justified.

Results and data are clear presented. All presented results relevant to the purpose of the research. Tables and figures are linked to key results and provide additional meaning to the written results.

Results are reported with an appropriate statistical support.

Discussion paragraph provide the context in which results are important. Connections are made to the broader literature, including what was cited in the Introduction.

All tables and figures are clear and add value to the text and highlight key aspects and they do not duplicate data elsewhere.

The discussion detailed the importance of the results and defined the ‘‘place’’ the outcomes have in the knowledge economy.

There are recommendations made for further work and direction.

The conclusions are reflective and supported by the findings presented in the manuscript.

Reply: We thank the reviewer for his/her considerations. We outline below our point-by-point replies.

Daily thermal variability had an effect on trunk diameters, the leaf area index (LAI), daily and seasonal water dynamics in grapevines?

Reply: Yes, trunk diameter fluctuations, leaf area index and daily and seasonal water dynamics respond to air temperature. Therefore, weather conditions were continuously monitored and daily maximum and minimum temperature values are presented in Figure 1. The influence of vapour pressure deficit was also highlighted in the manuscript.

Were foliar or soil fertilizers applied during the experiment, with the possibility of influencing the results?

Reply: Yes, soil fertilizers were applied during dormancy according to the grower's cultural practices. However, as the vineyard was equally managed in both training systems, no effects were due to these practices. For better clarification, the sentence was rewritten as follows:

Line 109: “The vineyard was managed (similarly in both training systems, e.g. soil fertilization) according to the grower's commercial cultural practices.”

Line 78  - crops (e.g., in tomato plants [30], lemon trees [31,32], peach trees [33,34], and olive trees [35,36]. – keep the same font size

Reply: The same font size is now applied.

Author Response File: Author Response.docx

Reviewer 3 Report

In the manuscript “Linking sap flow and trunk diameter measurements to assess water dynamics of Touriga-Nacional grapevines trained in Cordon and Guyot systems” the authors present sap flow (SF) and trunk diameter fluctuations (TDF) measurements of two differently trained vines during one particularly dry and hot growing seasons. The relations between SF, TDF and climate conditions and the differences between training systems are shown nicely, even though I would change the order of the figures to go from an overview of the whole growing season to some detailed periods. Introduction, Methods and discussion are presented well. To my knowledge the English is generally ok, with some minor expressions that should be checked. See the pdf attached for specific comments.

Comments for author File: Comments.pdf

Author Response

In the manuscript “Linking sap flow and trunk diameter measurements to assess water dynamics of Touriga-Nacional grapevines trained in Cordon and Guyot systems” the authors present sap flow (SF) and trunk diameter fluctuations (TDF) measurements of two differently trained vines during one particularly dry and hot growing seasons. The relations between SF, TDF and climate conditions and the differences between training systems are shown nicely, even though I would change the order of the figures to go from an overview of the whole growing season to some detailed periods. Introduction, Methods and discussion are presented well. To my knowledge the English is generally ok, with some minor expressions that should be checked. See the pdf attached for specific comments.

Reply: We are grateful to the reviewer’s comments. We do believe that the overall quality of the manuscript has been improved. We outline below our point-by-point replies. The corresponding changes in the manuscript are highlighted in red font.

It looks like the vines were still in a growing phase regarding radial stem growth during phase 1 (plot 3A+3D) but not anymore during the later phases. If the TDF measurements were continuous, it would be interesting to see why (probably due to decreasing soil water availability) the values of TDF dropped so much between the end of phase 1 and the start of phase 2 (and then increase a little between the end of phse 2 and the start of phase three). An additional figure with continuous TDF- (maybe just daily means) and SF- (daily sums) values for the whole measuring period would be interesting (could be placed in the supplementary material or add TDF+SF to figure 6 in an additional panel and show it earlier)

Reply: An additional figure has been added to the supplementary material (Figure S2. Daily means of trunk diameter fluctuations (TDF) and daily values (sums) of sap flow (SF) in Touriga-Nacional trained in the Cordon (C) and Guyot (G) systems during the growing season) and referred in the manuscript.

Personally I would show the daily courses (now Figure 5) before the XY-plot of SF and TDF (now Figure 4) because it facilitates the interpretation of the later. One could also think of placing them together in one figure, with the daily courses in the first two rows and the direct relation of SF and TDF in a third row (care has to be taken with the color scheme though).

Reply: We agree with the reviewer's comment. Therefore, the order between these two figures has been changed (figure 5 has been moved to figure 4 and figure 4 to figure 5) and the text was adjusted accordingly.

Instead of single days it would probably be more representative if average values for the three phases would be displayed in figures 4 and 5, but it's not absolutely necessary.

Reply: We understand the reviewer's comment. However, as the selected days were considered representative of the respective phases, we choose to keep the single days.

Looking at figure 3, i doubt that there is any real (irreversible) stem diameter growth after phase 2 and the later CG-values just represent the refilling of stem water storage during the night. "Cumulative increment" would therefore probably be a more correct term than "cumulative growth". (also see potential growth-tree water deficit concept by R. Zweifel (coming more from forestry) which could be interesting applied to your data, maybe in a separate paper... )

Zweifel R, Haeni M, Buchmann N, Eugster W (2016) Are trees able to grow in periods of stem shrinkage? New Phytol 211:839–849.

Zweifel R (2016) Radial stem variations - a source of tree physiological information not fully exploited yet. Plant Cell Environ 39:231–2.

Reply: The term “cumulative increment” (CI) is now used and replaces the term “cumulative growth” (CG). We thank the reviewer for the suggested references/approach that we would like to apply in a near future. A sentence was added as follows:

Lines 382-385: “Interestingly, the separation of the fractions of irreversible stem expansion induced by growth and reversible shrinkage and swelling induced by water deficit has been investigated in forest trees in order to better understand the processes of stem radius fluctuations [63,64].”

"pathway" is probably not the correct term here, I would use "daily course of solar radiation" or similar.

Reply: The term was changed accordingly (line 338).

looking at figure 5B+5C I would say that Cordon vines start closing their stomata at about the same time in the morning than Guyot vines (in the latest period maybe even earlier). However while stomata closure in Guyot increases during the day and therefore SF decreases, in Cordon vines stomata closure seems to be constant and they even open again in the afternoon leading to that late peak in SF for Cordon vines. Would be interesting to see how that late afternoon peak is related to e.g. soil moisture and if it gets smaller when the soil is driest.

Reply: We appreciate the reviewer’s comment. Stresses the relevance of understanding the water dynamics in the soil profile. Soil moisture was periodically measured in the present study, which did not allow to assess daily patterns. The sentence was rewritten as follows:

Lines 357-358: “These patterns were related with an earlier sap flow peak (corresponding to earlier stomatal closure) in both training systems and to a later second (and higher) sap flow peak during late afternoon (indicating stomata openness when VPD was decreasing) in Cordon-vines.”

see comment on page 8 regarding CG

Reply: The term “cumulative increment” (CI) is now used throughout the manuscript.

Any advice for the wineyard owner based on your measurements? Would you favor the Guyot training system as it appears to have a higher adaptive potential especially regarding climate change when extreme events are likely to occur more often?

Reply: A sentence was added to the section “conclusions”:

Lines 413-414: “In this way, the results support the selection of the Guyot as a training system better adapted to the projected climate change in the DDR as in other Mediterranean wine-growing regions.”

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

Thank you for your information abut the yield