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Peer review report 1 On “The dynamics of radial sap flux density reflects changes in stomatal conductance in response to soil and air water deficit”
Agricultural and Forest Meteorology 217 (2016) 79–80
Contents lists available at ScienceDirect
Agricultural and Forest Meteorology journal homepage: www.elsevier.com/locate/agrformet
Peer Review Report
Peer review report 1 On “The dynamics of radial sap flux density reflects changes in stomatal conductance in response to soil and air water deficit”
1. Original Submission 1.1. Recommendation: Minor Revision 2. Comments to Author: This paper investigated the efficacy of using sapflow (Js) and vapor pressure deficit (D) data to estimate stomatal conductance (gw) in trees growing within olive orchards under variable watering regimes. My first impressions of this study are positive; we often hear that we cannot infer transpiration (as part of gs) from sapflow measurements, but I have never quite bought that argument. There is a delay, and that is related to tree size, but water routing through the trunk is often water used by the canopy if we conduct the studies over an appropriate period of time. So, I like the topic. I also like the derived variable, Js/D, which makes lots of sense actually. Odd that others have not applied that variable widely. While I have a number of fairly minor comments below, I would like the authors to describe for us in more detail (in the discussion), the following: (1) exactly how these data would be used to set irrigation standards given that this approach is applied to olive orchards widely. Physically, how might that work? Orchards do not employ sapflow people? This is a big part of what is being used for justification of this study, and I want the authors to be sure they are not just saying this. A few sentences would help. (2) we need details on the limitations of this study. These are not well articulated. For example, these relationships will likely change as tree size increases. What about spatial sampling? Did you have enough trees for wide-area application, or for only those orchards? The story is too crisp, and that is not really the case. There are probably lots more that I cannot think of, which is why these details should be included as part of the discussion. The grammar and style are excellent, and the delivery wellthought-out. I like this paper a lot, and I think it is a good submission to this journal. The links to agriculture and forestry application are strong. Comments: 1) Abstract. Any way to add a little bit of data to the abstract perhaps to make a specific point?
DOI of published article: http://dx.doi.org/10.1016/j.agrformet.2015.11.013. 0168-1923/$ – see front matter http://dx.doi.org/10.1016/j.agrformet.2016.01.126
2) Introduction. Very well written. 3) L. 120-124. It is unclear how “detailed measurements” overcomes “replicating treatment plots”. Please explain. At face value, this is not technically possible, but perhaps I am not getting the meaning? 4) L. 117. Add the tree per hectare value here as well for a 7 × 5 m spacing, to match the TPA value of the other plantation. This just helps the reader visualize the differences between the plantations. 5) L. 128. 1.96 m wide? Is the referring to the crown width? Please describe. 6) L. 139-141. Add a line or two reminding the reader what the Compensation Heat Pulse (CHP) method is, assumes, and does. I find this really helpful, even for experienced sapflow users. There are so many techniques these days. I remember when there were just three! 7) Methods. Define data collection durations for sapflow from each plantation. It becomes clear later in the paper that many days were assessed, but state how many up front. 8) Scripting. The abbreviation for sapflow is Js (with J appearing in italics and the s appearing as a subscript without italics as you use on line 140). You cannot change this; it is established. So, your designations need to become Js1 (with s and 1 as subscripts). J1 (with 1 as a subscript) is not correct. This contention (Js1, etc) has been used previously, and it works. 9) Sample sizes. We need a summary table that details the sample sizes for measurements. I am confused by this. It sounds like you used very few trees (2 trees per treatment? What about replication?), which is a limitation of this paper (perhaps describe in uncertainties section?). Make sample sizes extremely clear with a table, perhaps even including individual tree measurements of dbh, height, crown area, etc. 10) L. 177-180. This is confusing. 3 leaves (replicates) and 2 measurements each? What is your experimental unit here? Sample unit is the leaf, experimental unit is the tree; not sure how you can have two replicates on a single tree if individual tree is your experimental unit? Experimental design language is getting mixed up. Also, report the light levels of readings from among plantations, and between shade versus sun leaves during measurements. These data are given by the Li-6400, and are very useful. I will argue here, critical to understanding your gs-to-Js/D curves. 11) L. 193-195. We need more information on statistical analyses used. There are several used (regression) that are not described here. Also, assumptions of why certain analyses would require a linear fit need to be provided. Student t-test? Why? Was there any factorial assignments (e.g., plantation by leave type)? Why not?
80
Peer Review Report / Agricultural and Forest Meteorology 217 (2016) 79–80
Perhaps incorporate some of that information from the Fernandez et al. (2001, 2006) papers here. 12) Figure 1. We need to see a time series of response for D versus 5, 10, 15, and 20 mm flows. Time on the x-axis, otherwise, your points are not being made to the degree that you think they are. 13) L. 217. Regression? Rationale and approach not previously introduced. 14) L. 224-226. Why would you elect not to show this? It may be that they do not really differ enough from the one you included to exclude? 10% is not much, and I think we need to see these. 15) L. 229. “Normalized” meaning “divided by”. OK. 16) Figure 2. Really good figure. Follows predictions for shade versus sun leaf response nicely. 17) Figure 3 and 4. Add “2.0” to the left-side x-axis. You will need to space the left and right side apart more to fit 2.0 and 0.0, but please do this. 18) L. 254. Wording. I do not think you have reported enough data points to show a hysteresis effect on these graphs? Certainly not a clear one. Not sure where it is. Same for Line 257, though I agree with your explanation of what may cause a hysteresis effect.
19) Figure 6. Good figure! Place “DOY = 14th of May of 2012” in the caption. 20) These relationships seem to work really well for the deficit irrigation treatments. Was gs really less responsive to D in deficit irrigation treatments (L. 322-324)? I see it potentially differently from the figures, but the r2 values support your view (L. 328). 21) L. 414-420. Explain this “decoupling” further. Exactly what are you saying, and more importantly, what might cause it in your specific system? 22) L. 436-439. Re-write this sentence. The point is unclear. 23) L. 439-441. That is just related to water availability to contribute to gs, right? 24) L. 442. I am still not seeing a hysteresis from the graphs presented. 25) L. 458. For example, using thermal dissipation probes? I hope so. I rely solely on these currently. 26) L. 473-474. I agree with this statement! 27) L. 487. 491. Should be “remarkably”. 28) L. 509. And larger trees? Ken Krauss UNITED STATES UNITED STATES
Contents lists available at ScienceDirect
Agricultural and Forest Meteorology journal homepage: www.elsevier.com/locate/agrformet
Peer Review Report
Peer review report 1 On “The dynamics of radial sap flux density reflects changes in stomatal conductance in response to soil and air water deficit”
1. Original Submission 1.1. Recommendation: Minor Revision 2. Comments to Author: This paper investigated the efficacy of using sapflow (Js) and vapor pressure deficit (D) data to estimate stomatal conductance (gw) in trees growing within olive orchards under variable watering regimes. My first impressions of this study are positive; we often hear that we cannot infer transpiration (as part of gs) from sapflow measurements, but I have never quite bought that argument. There is a delay, and that is related to tree size, but water routing through the trunk is often water used by the canopy if we conduct the studies over an appropriate period of time. So, I like the topic. I also like the derived variable, Js/D, which makes lots of sense actually. Odd that others have not applied that variable widely. While I have a number of fairly minor comments below, I would like the authors to describe for us in more detail (in the discussion), the following: (1) exactly how these data would be used to set irrigation standards given that this approach is applied to olive orchards widely. Physically, how might that work? Orchards do not employ sapflow people? This is a big part of what is being used for justification of this study, and I want the authors to be sure they are not just saying this. A few sentences would help. (2) we need details on the limitations of this study. These are not well articulated. For example, these relationships will likely change as tree size increases. What about spatial sampling? Did you have enough trees for wide-area application, or for only those orchards? The story is too crisp, and that is not really the case. There are probably lots more that I cannot think of, which is why these details should be included as part of the discussion. The grammar and style are excellent, and the delivery wellthought-out. I like this paper a lot, and I think it is a good submission to this journal. The links to agriculture and forestry application are strong. Comments: 1) Abstract. Any way to add a little bit of data to the abstract perhaps to make a specific point?
DOI of published article: http://dx.doi.org/10.1016/j.agrformet.2015.11.013. 0168-1923/$ – see front matter http://dx.doi.org/10.1016/j.agrformet.2016.01.126
2) Introduction. Very well written. 3) L. 120-124. It is unclear how “detailed measurements” overcomes “replicating treatment plots”. Please explain. At face value, this is not technically possible, but perhaps I am not getting the meaning? 4) L. 117. Add the tree per hectare value here as well for a 7 × 5 m spacing, to match the TPA value of the other plantation. This just helps the reader visualize the differences between the plantations. 5) L. 128. 1.96 m wide? Is the referring to the crown width? Please describe. 6) L. 139-141. Add a line or two reminding the reader what the Compensation Heat Pulse (CHP) method is, assumes, and does. I find this really helpful, even for experienced sapflow users. There are so many techniques these days. I remember when there were just three! 7) Methods. Define data collection durations for sapflow from each plantation. It becomes clear later in the paper that many days were assessed, but state how many up front. 8) Scripting. The abbreviation for sapflow is Js (with J appearing in italics and the s appearing as a subscript without italics as you use on line 140). You cannot change this; it is established. So, your designations need to become Js1 (with s and 1 as subscripts). J1 (with 1 as a subscript) is not correct. This contention (Js1, etc) has been used previously, and it works. 9) Sample sizes. We need a summary table that details the sample sizes for measurements. I am confused by this. It sounds like you used very few trees (2 trees per treatment? What about replication?), which is a limitation of this paper (perhaps describe in uncertainties section?). Make sample sizes extremely clear with a table, perhaps even including individual tree measurements of dbh, height, crown area, etc. 10) L. 177-180. This is confusing. 3 leaves (replicates) and 2 measurements each? What is your experimental unit here? Sample unit is the leaf, experimental unit is the tree; not sure how you can have two replicates on a single tree if individual tree is your experimental unit? Experimental design language is getting mixed up. Also, report the light levels of readings from among plantations, and between shade versus sun leaves during measurements. These data are given by the Li-6400, and are very useful. I will argue here, critical to understanding your gs-to-Js/D curves. 11) L. 193-195. We need more information on statistical analyses used. There are several used (regression) that are not described here. Also, assumptions of why certain analyses would require a linear fit need to be provided. Student t-test? Why? Was there any factorial assignments (e.g., plantation by leave type)? Why not?
80
Peer Review Report / Agricultural and Forest Meteorology 217 (2016) 79–80
Perhaps incorporate some of that information from the Fernandez et al. (2001, 2006) papers here. 12) Figure 1. We need to see a time series of response for D versus 5, 10, 15, and 20 mm flows. Time on the x-axis, otherwise, your points are not being made to the degree that you think they are. 13) L. 217. Regression? Rationale and approach not previously introduced. 14) L. 224-226. Why would you elect not to show this? It may be that they do not really differ enough from the one you included to exclude? 10% is not much, and I think we need to see these. 15) L. 229. “Normalized” meaning “divided by”. OK. 16) Figure 2. Really good figure. Follows predictions for shade versus sun leaf response nicely. 17) Figure 3 and 4. Add “2.0” to the left-side x-axis. You will need to space the left and right side apart more to fit 2.0 and 0.0, but please do this. 18) L. 254. Wording. I do not think you have reported enough data points to show a hysteresis effect on these graphs? Certainly not a clear one. Not sure where it is. Same for Line 257, though I agree with your explanation of what may cause a hysteresis effect.
19) Figure 6. Good figure! Place “DOY = 14th of May of 2012” in the caption. 20) These relationships seem to work really well for the deficit irrigation treatments. Was gs really less responsive to D in deficit irrigation treatments (L. 322-324)? I see it potentially differently from the figures, but the r2 values support your view (L. 328). 21) L. 414-420. Explain this “decoupling” further. Exactly what are you saying, and more importantly, what might cause it in your specific system? 22) L. 436-439. Re-write this sentence. The point is unclear. 23) L. 439-441. That is just related to water availability to contribute to gs, right? 24) L. 442. I am still not seeing a hysteresis from the graphs presented. 25) L. 458. For example, using thermal dissipation probes? I hope so. I rely solely on these currently. 26) L. 473-474. I agree with this statement! 27) L. 487. 491. Should be “remarkably”. 28) L. 509. And larger trees? Ken Krauss UNITED STATES UNITED STATES