Divergent water balance trajectories under two dominant  tree species in montane forest catchment  shifting from energy- to water-limitation

Zelíková, Nikol; Toušková, Jitka; Kocum, Jiří; Vlček, Lukáš; Tesař, Miroslav; Bouda, Martin; Šípek, Václav

doi:https://doi.org/10.5194/hess-29-6003-2025

Articles | Volume 29, issue 21

https://doi.org/10.5194/hess-29-6003-2025

© Author(s) 2025. This work is distributed under
the Creative Commons Attribution 4.0 License.

https://doi.org/10.5194/hess-29-6003-2025

© Author(s) 2025. This work is distributed under
the Creative Commons Attribution 4.0 License.

Articles | Volume 29, issue 21

Research article

|

05 Nov 2025

Research article |

| 05 Nov 2025

Divergent water balance trajectories under two dominant tree species in montane forest catchment shifting from energy- to water-limitation

Nikol Zelíková, Jitka Toušková, Jiří Kocum, Lukáš Vlček, Miroslav Tesař, Martin Bouda, and Václav Šípek

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Final revised paper (published on 05 Nov 2025)
Supplement to the final revised paper
Preprint (discussion started on 03 Sep 2024)

Interactive discussion

Status: closed

CC1:
'Supplementary file missing', Abinesh Ganapathy, 17 Sep 2024

Dear Authors,
It appears that the supplementary file for your manuscript is missing. Could you kindly update it at your earliest convenience?
Thanks

Citation: https://doi.org/10.5194/hess-2024-244-CC1
- AC1: 'Reply on CC1', Vaclav Sipek, 19 Sep 2024
  
  Publisher’s note: the supplement to this comment was edited on 27 September 2024. The adjustments were minor without effect on the scientific meaning.
  Dear Abinesh Ganapathy and editorial office,
  sorry for the inconvenience. I am enclosing the new manuscript PDF file, which also contains the supplementary material.
  I would also kindly ask the editorial office to replace the document.
  Kind regards,
  Vaclav Sipek (on behalf of all authors)
  
  Citation: https://doi.org/10.5194/hess-2024-244-AC1
RC1:
'Comment on hess-2024-244', Ronald Queck, 14 Oct 2024

The comment was uploaded in the form of a supplement: https://hess.copernicus.org/preprints/hess-2024-244/hess-2024-244-RC1-supplement.pdf

Citation: https://doi.org/10.5194/hess-2024-244-RC1
- AC1: 'Reply on CC1', Vaclav Sipek, 19 Sep 2024
  
  Publisher’s note: the supplement to this comment was edited on 27 September 2024. The adjustments were minor without effect on the scientific meaning.
  Dear Abinesh Ganapathy and editorial office,
  sorry for the inconvenience. I am enclosing the new manuscript PDF file, which also contains the supplementary material.
  I would also kindly ask the editorial office to replace the document.
  Kind regards,
  Vaclav Sipek (on behalf of all authors)
  
  Citation: https://doi.org/10.5194/hess-2024-244-AC1
- AC2: 'Reply on RC1', Vaclav Sipek, 07 Mar 2025
  
  The comment was uploaded in the form of a supplement: https://hess.copernicus.org/preprints/hess-2024-244/hess-2024-244-AC2-supplement.pdf
  
  Citation: https://doi.org/10.5194/hess-2024-244-AC2
RC2:
'Comment on hess-2024-244_rev2', Anonymous Referee #2, 07 Feb 2025

The comment was uploaded in the form of a supplement: https://hess.copernicus.org/preprints/hess-2024-244/hess-2024-244-RC2-supplement.pdf

Citation: https://doi.org/10.5194/hess-2024-244-RC2
- AC3: 'Reply on RC2', Vaclav Sipek, 07 Mar 2025
  
  The comment was uploaded in the form of a supplement: https://hess.copernicus.org/preprints/hess-2024-244/hess-2024-244-AC3-supplement.pdf
  
  Citation: https://doi.org/10.5194/hess-2024-244-AC3

Peer review completion

AR: Author's response | RR: Referee report | ED: Editor decision | EF: Editorial file upload

ED: Reconsider after major revisions (further review by editor and referees) (11 Mar 2025) by Miriam Coenders-Gerrits

AR by Vaclav Sipek on behalf of the Authors (31 May 2025) Author's response Author's tracked changes Manuscript

ED: Referee Nomination & Report Request started (03 Jun 2025) by Miriam Coenders-Gerrits

RR by Ronald Queck (12 Jul 2025)

Suggestions for revision or reasons for rejection

# Comments on the 2th manuscript

(a rendered text is in the attached pdf)

## Scientific significance:

Please refer to the first review from 2024-10-14.

## Scientific quality:

The authors provided a thoroughly revised manuscript, where even the title has changed.

The title and also the discussion indicates the investigation of the water balances of two forest stands. The within the text and also the section title in the methods part (2.3) this is restricted to a "soil water balance model".

Due to the lack of data, the used water balance model is based on very simple classical approaches. Nevertheless, the long time series of measured soil water content are valuable and need to be investigated. The analysis and discussion is encompassing, but needs at some points clarification.

## Specific Comments

The following comments are also made largely with reference to the first review.

### Comment#1

of the first review was "A weak point of the study is the approach used to calculate evapotranspiration. It does not explicitly regard the differences between spruce and beech. ..."

This Problem is still not solved. The differences between the sites is regarded by the soil conditions only. As the potential evapotranspiration for both sides is obviously calculated following a simple temperature function by McGuinness and Bordne (1972).

$PET = \frac{Re}{\lambda \rho} \frac{Ta+5}{100}$ for $Ta+5 > 0$, otherwise $PET=0$

The actual evapotranspiration (without interception) is then derived just by multiplying PET with the effective soil water content as proposed by (Feddes and Rijtema, 1972).

There seems to be no consideration of the difference in the phenological phases between the beech stand and the spruce stand and their influence on the transpiration.

If one compares the main four environmental drivers for tree transpiration (stomatal conductance, see Stewart, 1988): radiation, water vapour pressure deficit, temperature and soil moisture deficit. In mid In European forests, the influence of soil moisture deficit on tree transpiration is often the least significant. However this might change during droughts.

Since data for the Penman-Monteith (P-M) method has only been available at this location since 2008, it might be reasonable to extend the time series with this simple approach. However a comparison with a more refined method should be shown in the manuscript or at least in the supplementary.

### Comment#3

The relative homogeneity of vegetation is not a strong indicator for the representativity of the soil moisture measurements. The convenient placement of the sensors is also only a necessary condition but not sufficient. Soil structure, particularly in soils with a high skeleton content, is much more important for water drainage, root penetration and finally plant-available water.

The additional measurements with the UMS T8 indicate a reasonable correlation with the Thies sensors. Please, put the graphics also in the supplement.

### Comment#4

I still miss a graphical presentation of the soil moisture changes observed over time. Could you add the average values of soil moisture and runoff to Figure 2.

### Comment#5

Thank you for the exceedance probabilities of pressure head (Fig. 3). I am wondering why the probability for the entire period does not run in between the dry and the wet years. Why is the pressure head by 100 % probability of exceedance not the same for entire period and for wet years? Likewise, why is the pressure head by 0 % probability of exceedance not the same for entire period and for dry years? This should be the minimal and maximal value contained in both datasets respectively.

### Comment #6

Please, place a concise description of the categories directly after L293 "... seasonal development of their measured pressure heads.", i.e. move the part after L314 up to L293 and complete it with values (L314 is not a sum up, but a qualitative definition of the categories).

### Comment #7

The description of the model parameterisation and validation has improved with subsection 2.4, but it still needs some clarification. Please, make short sentences and use tables or lists for description of parameters. Clearly indicate which parameters are calibrated using which data and quality criteria.

If you use the runoff for calibration you need to define the areal distribution of beech and spruce in the catchment.

L230 You state "4 sub-periods for cross-validation". Cross-validation is a statistical technique used to evaluate how well the results of a model or analysis will generalize to an independent, unseen dataset. It involves partitioning the available data into subsets, training the model on some of these subsets, and testing it on the remaining ones. This process is repeated multiple times to ensure that the model's performance is robust and not just tailored to a specific portion of the data. ... It is not clear what is the unseen dataset which you use for the cross-validation.

I would assume that there is a difference in the parameter set for summer and winter, at least at the spruce site.

L240: "forward modelling"? Did you start with a known model and predict observations? It is more "inverse modelling", where you derive the model parameter, i.e. the model, from observations.

L241 "Besides the model run in the period of available soil water potential measurements (2000‒2021), the model was run also from 1975 to 1999 using the calibrated model parameters and available air temperature and precipitation sums to quantify annual AET for the entire observation period." This description is not really reproducible.

### Comment #9

How is the influence of tree type regarded?

You respond "The influence of tree type is reflected through different parametrization of the effective wetness (theta_E) restricting the rate of PET." However, the parameters theta_S and theta_R depend only on the soil type and soil structure, not on the tree type.

### Comment #10

These are indeed a complex relationships; one could also investigate the dependence on the soil moisture of the previous year or the runoff.

### Comment #1b

Fig. 7: Budyko plots are interesting. Please, compare the slidgly changed form in Renner et al. (2014). in my opinion it is somewhat clearer.

It is also to consider that in this study PET is only a linear function of the air temperature. A trend in PET is therefore initially a trend in temperature. AET is then the relative filled soil water storage times "Temperature" plus interception.

For PET/P < 1 the system is just energy limited, crossing the line of PET/P = 1 the system is additionally water limited. Instead of Fig 5 a) with the 5 year sums I would prefer a time series of AET/PET it might be that the shift between the two spaces in time is better visible using this relation.

# References

Renner M, Brust K, Schwärzel K, Volk M, Bernhofer C (2014) Separating the effects of changes in land cover and climate: a hydro-meteorological analysis of the past 60 yr in Saxony, Germany. Hydrol. Earth Syst. Sci. 18:389–405

Stewart JB (1988) Modelling surface conductance of pine forest. Agricultural and Forest Meteorology 43:19–35

## Presentation quality:

In general, the scientific results and conclusions are presented in a well-structured way. The number and quality of figures/tables is adequate (apart from the font sizes, they are often too small to print out). The English is comprehensible and generally good, but there are still some sentences that lack clarity and conciseness and need to be revised. Please, make the sentences as short as possible.

# Technical Corrections

The PDF file contains further comments.

Referee Report: PDF

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ED: Publish subject to minor revisions (review by editor) (23 Jul 2025) by Miriam Coenders-Gerrits

AR by Vaclav Sipek on behalf of the Authors (12 Aug 2025) Author's response Author's tracked changes Manuscript

ED: Publish as is (05 Sep 2025) by Miriam Coenders-Gerrits

AR by Vaclav Sipek on behalf of the Authors (19 Sep 2025) Manuscript

Short summary

Climate change in Central Europe results in the gradual replacement of spruce trees with beech. To model its potential impact, we used 22-year data of soil moisture under both tree species. The drier the summer season, the greater the difference between the two: the main reason was the higher transpiration of beech canopy compared to spruce. An accelerating transition of the Central European montane forest water balance from a fully energy-limited state towards water-limitation was documented.