The Effect of Woody Encroachment on Evapotranspiration in a Semi-Arid Savanna

Round 1

Reviewer 1 Report

Dear Authors,

 In my opinion, this study has ambiguities in terms of research method. The measurement of some parameters is ambiguous such as soil heat flux and net radiation. Also, the manuscript had not a suitable experimental design with some real treatments to evaluate evapotranspiration.

Best regards

 

 

Author Response

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Reviewer 2 Report

Comments on the “The Effect of Woody Encroachment on Evapotranspiration in a Semi-Arid Savana” by T. A. Aldworth et al.

 

Using in-situ observations, the authors analyzed the energy fluxes over a semi-arid region in South Africa. Especially, the authors analyzed the woody encroachment effect on ET. The manuscript is well organized, the science is well presented, and the results are well discussed. I was curious about the energy balance at the different sites.

Author Response

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Reviewer 3 Report

 

The manuscript is generally well written and the authors have collected a good amount of data and performed required analysis. Introduction is well written. Results are explained well. However, the following need to be addressed before publishing:

1.       The manuscript is difficult to read with a lengthy results and discussion section. I encourage authors to separate results and discussion.

May be diffusion can focus on (a) comparing EC and SR methods, and (b) annual ET higher (sometimes 80%) than annual precipitation.

I am not suggesting re-writing. Just suggesting re-organizing so that it will be easy to read and follow.

2.       The methods only show the equations for H, For SR method they refer to a publication but since you are presenting ET, the equation should be mentioned here. For EC (section 3.2.2) no information is presented on how ET will be calculated once H is calculated.

 

3.       L580-581 ---- The SR1 approach with EC calibration was found to be a viable method for estimating 580 ET in a mopane-encroached, semi-arid savanna located in north-eastern South Africa.

I am not sure if I follow, the methods say that ET will be estimated using EC and SR methods and then they will be compared. Is one method used in calibrating other methods. What does “SR1 approach with EC calibration mean”. Please discuss this in Methods.

 

4.       L560-578; is this a region with shallow ground water?

 

5.       Please add a limitations section.

Author Response

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Reviewer 4 Report

The aim of the article is to determine the effect of mopane encroachment on ET in a semi-arid savanna located in South Africa. The surface renewal method is applied and specifically the SR1 method after calibrating it via Eddy Covariance. They found that woody encroachment (WE) can increase ET, at least during wetter years, with potential effect on groundwater and soil water recharge. Moreover, they reported seasonal trends for ET and that the annual ET exceeded precipitation.

English is excellent and fluent.

Few typos are found. Please mind that % is placed after a number without space (e.g., 5%) , whereas units need space (e.g. 2 m). Moreover, we do not write for example 2-10% but 2%-10%. Please follow those rules throughout the manuscript.

The text is well structured and the meaning is clearly conveyed.

Methodology and equipmnet are clearly described and the applied methods are well theoretically supported.

The number and the quality of figures are satisfactory to support the results.

The findings are adequately discussed. 

 

However, the following comments should be considered:

Few references could be added regarding the usage of the selected statistical metrics in relevant studies of the recent literature.

Regarding the linear regression analysis between HSRDT (or HSR1) and HEC, I believe that the used statistical metrics (i.e., R^2, RMSE and RD) are not enough to strongly support the selection of SR1. The authors could consider to calculate few more metrics such as: Mean Bias (MB), Mean Absolut Error (MAE) and/or their normalized formulae (NMB, NMAE and NRMSE) which are employed in the relevant literature. The normalized version disentangles the units from the metrics and therefore, their values are easily comprehensible and comparable.

You could retrieve the metric formulae from the following studies:

https://doi.org/10.3390/hydrology9070124

https://doi.org/10.3390/agriculture12050612

https://doi.org/10.3390/rs14215446

Lines 560-567: You attribute the ET exceedance only to vegetation (depth of grass roots etc). Where soil evaporation is placed in this reasoning? Why not soil water to be directly evaporated from a greater depth of the soil profile as evaporation progresses, due to the increased evaporative demand? Please justify the assertion or revise.

Kind regards

Author Response

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Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

Dear Authors,

 In my opinion, the manuscript had not a suitable experimental design with some real treatments to evaluate evapotranspiration.

Best regards

Reviewer 3 Report

authors addressed comments. 

Reviewer 4 Report

Authors addressed my comments. I suggest acceptance.