Is the reputation of <i>Eucalyptus</i> plantations for using  more water than <i>Pinus</i> plantations justified?

White, Don A.; Ren, Shiqi; Mendham, Daniel S.; Balocchi-Contreras, Francisco; Silberstein, Richard P.; Meason, Dean; Iroumé, Andrés; Ramirez de Arellano, Pablo

doi:https://doi.org/10.5194/hess-26-5357-2022

Articles | Volume 26, issue 20

https://doi.org/10.5194/hess-26-5357-2022

© Author(s) 2022. This work is distributed under
the Creative Commons Attribution 4.0 License.

https://doi.org/10.5194/hess-26-5357-2022

© Author(s) 2022. This work is distributed under
the Creative Commons Attribution 4.0 License.

Articles | Volume 26, issue 20

Research article

|

27 Oct 2022

Research article |

| 27 Oct 2022

Is the reputation of Eucalyptus plantations for using more water than Pinus plantations justified?

Don A. White, Shiqi Ren, Daniel S. Mendham, Francisco Balocchi-Contreras, Richard P. Silberstein, Dean Meason, Andrés Iroumé, and Pablo Ramirez de Arellano

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Final revised paper (published on 27 Oct 2022)
Supplement to the final revised paper
Preprint (discussion started on 16 Jun 2022)
Supplement to the preprint

Interactive discussion

Status: closed

RC1:
'Comment on hess-2022-200', Michael Ryan, 08 Aug 2022
The study did a meta-analysis of Eucalyptus versus Pinus water annual Evapotranspiration (ET) for 57 closed-canopy plantations and used the relationship between Vegetation Evaporation Efficiency (VEE, ET/Potential ET (PET)) versus Climate Wetness Index (CWI, Precipitation (P)/PET) to assess differences between the genera using an Analysis of Covariance. The range of ET, P, PET and CWI was similar for the two genera. The analysis concluded that both genera had an identical relationship of Vegetation Evaporation Efficiency with Climate Wetness Index, contrary to current expectations. The study clearly shows that differences in genera planted are unimportant in determining ET compared to the differences between plantation forests and the prior land use (pasture or native forest).

This is an important, very sound study and very clearly presented in a thorough, well-written manuscript. In addition to the comparison of ET by the genera, the Discussion also argues that the timing of measurements during the growth of plantations and the length of the rotation are important considerations for assessing differences in ET among genera.

Comments:

A regression of Vegetation Evaporation Efficiency with Climate Wetness Index has ET/PET as the dependent variable and P/PET as the independent variable, with PET as the denominator of both variables. Such normalizing may influence the goodness of fit and perhaps the shape of the fitted function. I recommend redoing the analysis with just ET versus P as a cleaner test of the differences between genera.

While differences in wood production between genera are briefly mentioned, some more discussion on this topic would be useful. If wood production per unit ET differed between genera, that would be an important consideration for forest management. My expectation is that Eucalyptus would have a greater wood production per unit ET than Pinus.

It would also be useful to test if there are any differences between the different methods for estimating ET in the relationship between Vegetation Evaporation Efficiency with Climate Wetness Index or ET versus P.

The data spreadsheet included as Supplemental Material is useful but should have the column names defined and the data used in the paper identified specifically.

Minor edits:

L91: ‘have found that not observed’ should be ‘have not observed’.

L144: Should ‘Energy Limit’ be included in the definitions?

L178: What is reference evaporation?

L341 and elsewhere: limit numbers to three significant digits.

L411: ‘similar (Beynon and Doody, 2015), Figure 3)’ should be ‘similar (Benyon and Doody, 2015, Figure 3).
Citation: https://doi.org/10.5194/hess-2022-200-RC1
- AC1: 'Reply on RC1', Don White, 11 Aug 2022
  
  Thanks Dr Ryan for your review.
  I will not resond to the minor edtorial comments here
  Your suggestion regarding plotting ET v P is a good one. In Zhang et al 2004, 2004 a number of models are proposed to relate ET to P in Table 1 (same table number in both papers) and we have, in response to your review fitted all models in this table. In each case there was no significant difference between the Pines and Eucalypts. However as you note in all these models P ares normalsed WRT PET. Zhang et al argues this is necessary to satisfy the energy limit.
  We then fitted a simple exponential rise to a max to the relationship between ET and P. The results were still non-significant but the P value was much lower (0.115). This was due to a snall number of points of high leverage that are from Euc sites on deep soils. This is very useful and strengthens the discussion regarding the importance of site - on deep soils, as David Scott noted in his South African work, Eucs have the potential to have a larger impact than pines, but when all sites are analysed together the effect is non-significant. we will expand this discussion based on these results
  We analysed the effect of messurement method - and all comparisons were non-significant.
  Thanks for these helpul suggestions and comments
  Don - on behalf of all authors
  
  Citation: https://doi.org/10.5194/hess-2022-200-AC1
- AC4: 'Reply on RC1', Don White, 22 Aug 2022
  
  Once again thanks for this review
  We have revised the MS based on your suggestions.
  I recommend redoing the analysis with just ET versus P as a cleaner test of the differences between genera. As suggested we have redone the analysis. As noted in my earlier comment the difference between genera is still non-significant. This is now included as an extra figure. It also provided additional basis for further discussion of the effect of soil depth
  While differences in wood production between genera are briefly mentioned, some more discussion on this topic would be useful. We have added a couple of sentenced to he discussion regarding wood / water
  It would also be useful to test if there are any differences between the different method. We have analysed the data to compare between methods. No effect of measurement method was detected
  We have also added more detail to the supplementary materias as suggested
  
  Citation: https://doi.org/10.5194/hess-2022-200-AC4
CC1:
'Comment on hess-2022-200', Auro Almeida, 09 Aug 2022

Follow minor comments and suggestions to the paper. It was not my intention to make a detailed review of the paper

Line 330 should be Rio Grande do Sul instead than Rio Grande du Sol
Table 1
In Almeida et al 2016 shows the results of two regions Terra Dura and Ponta das Canas, the Table show only Terra Dura, I would suggest including the two group of catchments
In Reichert et al 2017 the Region should be Ponta das Canas and the state is Rio Grande do Sul and not Rio Grande du Sol
Soares and Almeida 2001 the Method is 3 instead than 2. The same catchment is presented in Almeida et al 2007 containing 8 years of results however it hasn’t been included in the Table
General comment
The authors meta-analysis considering the two genera is valid contribution, however there are variations in water use by different species in the genera that haven’t been adequately explored in the paper. This is important to avoid generalisation and misinterpretation. The authors cite examples of E. globulus, E. grandis, P. radiata, P. patula but no further comments are made on the variability of the species. There are many studies showing also variability of water use and water use efficiency between clones of the some species and I think this should be recognised and mentioned somewhere in the paper.
Auro Almeida

Citation: https://doi.org/10.5194/hess-2022-200-CC1
- AC2: 'Reply on CC1', Don White, 11 Aug 2022
  
  Thanks Dr Almeida for taking the time to comment on our paper.
  Your minor editorial comments are all helpful and correct errors in the paper.
  Regarding the comparison between species. There is not enough replication for all species to compare individual species. A simple comparison of means suggests tripcal and temerate species are not different for either genus.
  As for variation within species. The intent of ths paper was to show that at long time intervals and large scales, the often observed variation at smaller scales tends to disappear. However, we will add a couple of sentences to the dicussion regarding the numerous papers that report species and within species variation.
  Thanks for your observations and for taking the time to read the paper
  Don (on behalf of all authors)
  
  Citation: https://doi.org/10.5194/hess-2022-200-AC2
RC2:
'Comment on hess-2022-200', Anonymous Referee #2, 11 Aug 2022

I think this is a very useful contribution to the afforestation debate. The paper is very well written and presented. I do not have any particular criticisms. I note a posted comment regarding variability in species that, in an ideal world of data, would be good to delve into, but I suspect there are not the data to do this well. However it could be a discussion point.

One section perhaps could be reworded; in the para beginning line 97 there is a statement that .."there seems to be differences between etc." and then suggests studies that show similar outcomes. Could be just me, but seemed not quite the right text.

My other comments are around the Discussion, which I think is great. I suspect the section from Line 471-485 is the nub of the "thirsty eucalypts" concept that many have. What are people comparing when thinking about water use; is it mature closed canopy stand or a young stand going hard? What is the soil moisture status at the time of planting? etc.. with the pinus stands apparently having consistently longer rotations, there is a greater likelihood of attaining a hydrologic state matched to the site resources.

There is a paper (Lane et al. 2005 H.Hydrol. 310) that compares changes in streamflow for mainly South Africa and Australian catchments. The lone eucalypt site plots right in the middle of the flow reductions. These magnitude of these reductions appeared to be partly a function of soil depth/storage. This analysis also looked at the timing of flow reductions which also speaks to the age and rototion discussion.

The authors may or may not feel like any of the above might be useful discussion material.

Overall, I commend the authors for a very good paper

Citation: https://doi.org/10.5194/hess-2022-200-RC2
- AC3: 'Reply on RC2', Don White, 11 Aug 2022
  
  Thanks for taking the time to review the paper. Your observation on soil depth is a good one and I will certainly read and cite the paper you suggest. RC1 suggested some additional analysis which highlighted s the high leverage of Euc sites on deep soils. This reinforces the need to qualify the general observations for deep soils. We will stengthen this part of the discussion and make this qualification clear in the abstract, highlights and discussion.
  Don (on behalf of all co-authors)
  
  Citation: https://doi.org/10.5194/hess-2022-200-AC3

Peer review completion

AR: Author's response | RR: Referee report | ED: Editor decision

ED: Publish subject to minor revisions (further review by editor) (30 Aug 2022) by Adriaan J. (Ryan) Teuling

AR by Don White on behalf of the Authors (16 Sep 2022) Author's response Author's tracked changes Manuscript

ED: Publish as is (21 Sep 2022) by Adriaan J. (Ryan) Teuling

AR by Don White on behalf of the Authors (29 Sep 2022) Author's response Manuscript

Short summary

Of all the planting options for wood production and carbon storage, Eucalyptus species provoke the greatest concern about their effect on water resources. We compared Eucalyptus and Pinus species (the two most widely planted genera) by fitting a simple model to the published estimates of their annual water use. There was no significant difference between the two genera. This has important implications for the global debate around Eucalyptus and is an option for carbon forests.