Dr Jacob Crous is thanked for his review and comments, and his contribution to the content of the paper. Authors agree with Dr Crous that the use of a word “subtropical regions” is not accurate in the context of the findings of this paper. Authors suggest substituting “subtropical regions” with “regions where soil water is not limiting”. Authors further agree with Dr Crous that in our study, there is no solid scientific proof supporting our statement that Eucalyptus water use has a potential to exceed pine in regions where soil water is not limiting”. Eucalyptus and pine comparative water use studies reported that eucalypts are not profligate consumers of water than pine (Myers et al. 1995, White et al. 2021). Authors will therefore adjust this statement in the manuscript and further clarify that water use results could be influenced by climate, soils, experimental methodologies etc, as stated by Dr Crous.

References:

White, D. A., Silberstein, R. P., Contreras, F. B., Quiroga, J. J., Meason, D. F., Palma, J. H. N., de Arellano, P. R.: Growth, water use, and water use efficiency of Eucalyptus globulus and Pinus radiata plantations compared with natural stands of Roble-Hualo Forest in the coastal mountains of central Chile, For. Ecol. Manage., 501, 119675-119676, https://doi.org/10.1016/j.foreco.2021.119676, 2021.

Myers, B. J., Theiveyanathan, S., O’Brien, N. D. O., Bond, W.J. 1996. Growth and water use of Eucalyptus grandis and Pinus radiata plantations irrigated with effluent. Tree physiology 16: 211-219.

Authors would like to thank Miriam Coenders-Gerrits for the insightful comments that have added a valuable contribution to the manuscript. Authors response to her comments are indicated below:

1. “you conclude that the transpiration is GN is lower than in Pinus due to the lack of water. Of course this is true: transpiration reduces as water becomes more limited (fig 5). However, I wonder if this very low matrix potential is not caused by the high transpiration rates of GN before the study period? So that the GN depleted already the soil? (feedback mechanism)”. Authors agree with this possibility, as literature states that transpiration rates are generally high in Eucalyptus early in the rotation and decrease as trees mature. With our GN trees close to maturity during the study period, it is possible that high rates of transpiration depleted soil water greater than recharge before the study period.
2. The contribution of fog. In line 70 you say that fog precipitation is significant. How does this affect your results? How reliable are your precipitation observations? And how would this affect your interception results? We have modified this to read, ‘the contribution of fog could be significant’. The word precipitation should be changed to rainfall. The rainfall has been measured accurately, although rainfall can be highly variable, we believe the rainfall measurement represent the actual rainfall accurately. The accuracy of the rainfall results would impact the interception because the interception is based on the rainfall. We used a Texas instruments raingauge at a standard height with a backup raingauge in case of failure.
3. “Units/dimensions: I think the authors should do a carefull check on the units. In my view transpiration is a flux, thus having a time dimension. Therefore, most of the numbers given in the paper should have the unit mm/day or mm/month or mm/year (instead of mm). Some quick examples: L19, 151 (liter),  183 (mm/year), 213, 214, 215, 242, 265, 285 (mm/year), fig 3d (mm/day) and caption, fig 5 (rainfall mm/day), fig 5 (T=mm/day), fig 6 (rainfall mm/day), fig 8 (rainfall mm/day) and caption, fig 11 (mm/month) plus caption” Authors agree with Miriam and this will be incorporated in the manuscript.
4. “Equations 3 +4: I would make this liniear. No need (and reason) for polynomial”. The best regression co-efficient was found when both equations were polynomial, which is the reason why they were made polynomial, however if the reviewer would prefer linear then that would be acceptable to the authors as the difference in the model fit is small.
5. “Section 4.3: I would keep this section for qualitative as you did not measure interception and soil evaporation. Especially, since you have fog the interception could be very high”. Authors agree, and will keep this section for qualitative comments.
6. “L187: unit of Is should be MJ/m2/d. Also check fig 3b”. Authors have noted this comment and adjustment will be made throughout the manuscript.
7. “I would recommend to write all parameters in the text in italic and make use of subscript (e.g.,  Tair => T_air)”. Authors are in agreement and will modify the document throughout.

Authors would like to thank Miriam Coenders-Gerrits for the insightful comments that have added a valuable contribution to the manuscript. Authors responses to comments are indicated below in bold writing:

1. “you conclude that the transpiration is GN is lower than in Pinus due to the lack of water. Of course this is true: transpiration reduces as water becomes more limited (fig 5). However, I wonder if this very low matrix potential is not caused by the high transpiration rates of GN before the study period? So that the GN depleted already the soil? (feedback mechanism)”. Authors agree with this possibility, as literature states that transpiration rates are generally high in Eucalyptus early in the rotation and decrease as trees mature. With our GN trees close to maturity during the study period, it is possible that high rates of transpiration depleted soil water greater than recharge before the study period.
2. The contribution of fog. In line 70 you say that fog precipitation is significant. How does this affect your results? How reliable are your precipitation observations? And how would this affect your interception results? We have modified this to read, ‘the contribution of fog could be significant’. The word precipitation should be changed to rainfall. The rainfall has been measured accurate, although rainfall can be highly variable, we believe the rainfall measurement represent the actual rainfall accurately. The accuracy of the rainfall results would impact the interception because the interception is based on the rainfall. We used a Texas instruments raingauge at a standard height with a backup raingauge in case of failure.
3. “Units/dimensions: I think the authors should do a carefull check on the units. In my view transpiration is a flux, thus having a time dimension. Therefore, most of the numbers given in the paper should have the unit mm/day or mm/month or mm/year (instead of mm). Some quick examples: L19, 151 (liter),  183 (mm/year), 213, 214, 215, 242, 265, 285 (mm/year), fig 3d (mm/day) and caption, fig 5 (rainfall mm/day), fig 5 (T=mm/day), fig 6 (rainfall mm/day), fig 8 (rainfall mm/day) and caption, fig 11 (mm/month) plus caption” Authors agree with Miriam and this will be incorporated in the manuscript.
4. “Equations 3 +4: I would make this liniear. No need (and reason) for polynomial”. The best regression co-efficient was found when both equations were polynomial, which is the reason why they were made polynomial, however if the reviewer would prefer linear then that would be acceptable to the authors as the difference in the model fit is small.
5. “Section 4.3: I would keep this section for qualitative as you did not measure interception and soil evaporation. Especially, since you have fog the interception could be very high”. Authors agree, and will keep this section for qualitative comments.
6. “L187: unit of Is should be MJ/m2/d. Also check fig 3b”. Authors have noted this comment and adjustment will be made throughout the manuscript.
7. “I would recommend to write all parameters in the text in italic and make use of subscript (e.g.,  Tair => T_air)”. Authors are in agreement and will modify the document throughout.

Authors would like to thank David Scott for his valuable comments to the manuscript. Response to his comments by authors is below in bold writing:

1. the comparison between eucalypts and pine is relevant, but there is not enough hard data of make a definitive determination of their relative effects.  We agree and have therefore not been definitive in our statements regarding their relative water use. We have recommended that further measurements and hard data for comparison be collected.
2. I think that the title and abstract should soften the emphasis on this comparative water use.  We will soften the emphasis on this comparison in the title and water use. We could take out the word ‘comparative’ from the title, so it reads “Water-use by fast-growing Eucalyptus grandis x E. nitens clonal hybrid and Pinus elliottii near the Two Streams Research Catchment, South Africa”.
   
   
   
   
3. Interesting data is presented on the comparative transpiration, but the other elements of total water use are poorly quantifiable, so the final comparison of ET by the two species is little better than speculative.  Specifically, the crops are very different ages and thus a direct comparison is not convincing (at least not without a lot more convincing information on why a comparison is reasonable). Noted and agreed. More data would be convincing but we felt this was a good starting point and acknowledge the speculation although the estimations of soil ET and rainfall interception were based on results from numerous studies in the literature. The trees are at different ages but comparable in terms of their stage in their growth cycle and therefore we felt warrant comparison. We agree and recommend more comparative work and data collection. Measurements of ET in particular would be beneficial but obviously quite costly.
4. Secondly, the soil water component is poorly defined, and the soil & interception figures are estimated from such general sources (of dubious applicability) that the errors on those estimates make the overall estimates speculative.  I think these are serious flaws, but I think the information on direct measurements in the paper are still important and useful.  But the authors should not attempt to close the water balance except in a broad and speculative way. We will focus on the results of transpiration and limit the results of the estimated water balance at each site to a broad and speculative discussion.
5. My annotated version of the manuscript contains several parts where the language or expression is lacking and can be improved. Authors thank David Scott for his corrections in the document. We will address those sections and improve the expression.
6. Section 2.5 on the soil water content left me puzzled, and I think that it and the later references to the soil water store, are wrong.  Soil wetness is presumably measured with some sort of TDR instrument, that give a volumetric wetness at the 3 depths (this should be stated more clearly in the text - I don't know what a CS616 sensor is). Yes, the soil water content was measured with a TDR probe. A clear definition of soil water measurement measuring equipment will be included in the manuscript as well as the conversion to soil water potential

6.1 These volumetric wetness figures could be used to estimate a depth of water in the profille, which is a measure of the absolute amount of water available to the trees (PAW).  It doesn't make sense to me to go through some sort of model to estimate the approximate soil water potentials that these wetness figures would relate to (section 3.2).  If the objective is to consider plant available water, then it is best to use volumetric wetness, and convert these to an estimate of a depth of water in the soil profile at a each particular point in time.

We used the Hyprop system to measure the soil retention curve of the soils and were able to then convert the volumetric water content using a robust method into soil water potential. We felt it would be useful to present soil water retention as this shows the dryness of the soil quite well, independent of particle size distribution. If the reviewer would prefer us to show it as an absolute depth of water in the soil we are able to do that.

6.2 With the deepest probe at 60 cm (properly 0.6 m in SI units), there is a large uncertainty about how much water is still available to the trees at depths below say 0.75 m?  The estimates of soil water are therefore incomplete, and only give an indication of the real situation. The information on the response of the trees to increase water availability immediately after rain, or in the dry season, are interesting and useful, but it needs to be acknowledged that the trees may have access to water in parts of the profile that have not been monitored.  {Consider Peter Dye's measurements of eucalypts under stress - 1996, Tree Physiology, 16: 233-238, which showed water was being used to 8 m below the surface and beyond}. Root experiments conducted in commercial forest stands (Laclau et al. 2001, Fabiao et al. 1995) reported that majority of fine roots are located at the soil surface (top one meter of soil) decreasing with increase in soil depth. However, authors are aware that pine and Eucalyptus trees develop a dirmophic root system (deep taproot and shallow fine roots), with a tap root as deep as the height of a trees, to increase chances of sourcing water. We therefore agree we David Scott that trees in our study probably sourced water stored deep in the soil profile and authors will indicate this possibility in the manuscript. We will acknowledge that the trees may have access to water in deeper parts of the profile that are not monitored.

6.3 Related to the point in (b), more should be said about the soil profiles, and this should include materials below the conventional soil profile and include the substrate beneath, from which water may be drawn.  Is it hard rock, or is it decomposing and permeable (as well as accessible to tree roots?). Authors agree with David and details of the soil profile will be included where available. The substrate is unconsolidated material with rock only at about 40 m.

References

Fabiao A, Steen E, Katterer T, Ribeiro C, Araujo C. 1995. Development of root biomass in an Eucalyptus globulus plantation under different water and nutrient regime. Plant and Soil 168: 215-223.

Laclau JP, Arnaud M, Bouillet JP, Ranger J. 2001. Spatial distribution of Eucalyptus roots in a deep sand soil in the Congo: relationships with the ability of the stand to take up water and nutrients. Tree Physiology 21: 129-136.