the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Modeling water balance components of conifer species using the Noah-MP model in an eastern Mediterranean ecosystem
Abstract. Few studies have investigated the performance of land surface models for semi-arid Mediterranean forests. This study aims to parameterize and test the performance of the Noah-MP land surface model for an eastern Mediterranean ecosystem. To this end, we modeled the water balance components of two conifer species, Pinus brutia, and Cupressus sempervirens, in a plantation forest on the Mediterranean island of Cyprus. The study area has a long-term average annual rainfall of 315 mm. Observations from 4 sap flow and 48 soil moisture sensors, for the period from December 2020 to June 2022, were used for model parameterization. A local sensitivity analysis found that the surface infiltration (REFKDT), hydraulic conductivity (SATDK), and stomatal resistance (RSMIN) parameters had the highest impacts on the soil water balance components and transpiration. The model performed better during the wetter 9-month validation period (379 mm rain) than during the drier 10-month calibration period (175 mm rain). Average soil moisture in the top 60-cm of the soil profile was reasonably well captured for both species (daily NSE > 0.70 for validation). Among the three soil layers, the second layer (20–40 cm) showed better simulation performance during both periods and for both species. The model exhibited limitations in simulating transpiration, particularly during the drier calibration period. Inclusion of a root distribution function in the model, along with the monitoring of soil moisture below the 60-cm soil depth in the field, could improve the accuracy of model simulations in such water-limited ecosystems.
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RC1: 'Comment on hess-2024-107', Anonymous Referee #1, 09 Jul 2024
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Dear authors,
The manuscript titled “Modeling water balance components of conifer species using the Noah-MP model in an eastern Mediterranean ecosystem” aims to parameterize and test the performance of the LSM Noah-MP on an eastern Mediterranean planted forest. The authors monitored the sap flow of two coniferous species and soil moisture over 19 months to achieve the goal. The manuscript reads very well. However, while the presented study is both interesting and timely, some issues need to be addressed before the manuscript can be accepted for publication.
My main concern is about the number of sap flow sensors, only two sap flow sensors per species, which in my opinion is quite small. To overcome this significant limitation, you must make clear that transpiration variability within species in the plantation is sufficiently low. Additionally, concerning tree variability, the standard error for tree dimensions is missing. Providing this information will inform readers about the representativeness of the studied trees within the plantation.
It would be important to have some more information concerning the water use strategies and rooting systems of the studied species, Pinus brutia and Cupressus sempervirens, in the introduction (eventually around lines 40-48), to help results interpretation and subsequent discussion.
The mention of the reported or studied water balance components (transpiration and soil moisture?) in the abstract is advised.
The choice of the parameter designation is not very straightforward (e.g. REFKDT or SATDK), the manuscript would benefit with the use of simpler designations or the name of the parameters
Figure 1: it would be interesting to distinguish between pine and cypress at the site, and eventually identify which trees were used for sap flow
Please consider my specific questions, technical corrections or suggestions on the attached pdf file.
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RC2: 'Comment on hess-2024-107', Anonymous Referee #2, 25 Jul 2024
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The manuscript "Modeling water balance components of conifer species using the Noah-MP model in an eastern Mediterranean ecosystem" presents a study on simulating water balance components in Mediterranean coniferous forests using the Noah-MP land surface model. The methodology, which combines field observations with advanced modeling techniques, is robust and well-documented. Nevertheless, my major concern is that the scientific contribution and broader implications of the study are not fully articulated. The study primarily focuses on calibrating the model using observational data but lacks a clear discussion on the implications of these findings for broader scientific understanding or practical applications. For example,
- The Introduction does not adequately discuss the potential implications of the study’s findings. There is no mention of how the results might contribute to model development or forest management practices. Also, the introduction mentions several studies but does not critically engage with them to highlight what has been done and what remains to be explored. It is not clear how the research gap (I assume it is "no research in the literature has combined field observations with land surface models (LSMs) to estimate water balance components in Mediterranean coniferous forests.") would be relevant for new understanding or methodological advances.
- In the Discussion and Conclusions, while the comparison with previous studies is informative, it lacks depth in explaining why certain differences or similarities occur. For instance, it is still not clear why strong water limitation in your study area might influence these sensitivities differently than in other regions. Still, the broader implications of the sensitivity analysis findings for model calibration, validation, and application are not sufficiently discussed. It would be appreciated to discuss how your results contribute to the understanding of the effects of soil and vegetation parameters on water balance components under different climatic conditions.
- In addition, the study observes better model performance during the wetter validation period compared to the drier calibration period. I suggest that an additional calibration-validation framework can be considered. Specifically, the authors could calibrate the model using data from the wetter period (September 2021 to June 2022) and validate it using data from the drier period (December 2020 to August 2021). By reversing the calibration and validation periods, the study can assess whether the model is robust across different hydrological conditions.
- Last but not least, the study only uses a few site observations, which raises my concerns about the generalizability of the findings. While this may not be the focus of the study, modeling only a single tree may lead to an oversimplified representation of the ecosystem. I recommend discussing the limitations of this approach and suggesting ways to improve the generalizability of future studies.
Overall, while this paper presents a comprehensive study that calibrates the Noah-MP model for Mediterranean coniferous forests, it falls short in articulating the significance and broader impact of its findings. I am not an expert in the specific field, so I cannot definitively judge the paper's actual contribution in its current form. I recommend that the editor assess its suitability for publication.
Citation: https://doi.org/10.5194/hess-2024-107-RC2
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