the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 02 Dec 2025
National-Scale Inventory based Climate Impact Analysis of the Nitrogen Balance, including all Nitrogen Fluxes using Process-Based Modelling with the LandscapeDNDC Model and EURO-CORDEX Ensembles for Greece
Abstract. In this study, we have simulated inventories of arable production and soil carbon and nitrogen cycling on a national scale (0.25 × 0.25-degree) for Greece with the bio-geochemical ecosystem model LandscapeDNDC. Based on observation data, we have aggregated for each grid cell 4 most likely crop rotations, including nitrogen and manure fertilization, tilling and irrigation. The arable management was continuously projected into the future until 2100, while plant phenology was adapted to local conditions, general properties of the arable management were kept constant into the future, such as the selection of crops or the share of irrigated arable land. To understand the impacts of climate change, we used the EURO-CORDEX-11 regional climate ensemble to drive the LandscapeDNDC impact model under scenarios RCP4.5 (16 datasets) and RCP8.5 (32 datasets). The simulation timespan was from 1990 until 2100, using the first 10 years as spin-up to obtain equilibrium in the model's internal carbon and nitrogen pools from the model initialization.
Arable production declines from 2045 onwards by 9.5% or 144 kg C ha-1 yr-1 under RCP4.5 and by 29% or 484 kg C ha-1 yr-1 towards 2100. At present, the ensemble results show an average soil carbon loss of 122.1 kg C ha-1 yr-1 versus 139.7 kg C ha-1 yr-1 in the future. The gaseous outfluxes of the ensemble simulations show N2O emissions of 0.494 to 0.453 kg N2O–N ha−1 yr−1, NO emissions of 0.031 kg NO–N ha−1 yr−1, N2 emissions of 4.806 to 3.377 kg N2–N ha−1 yr−1, NH3 emissions of 24.662 to 35.040 or 34.205 kg NH3–N ha−1 yr−1 and nitrate leaching losses from 54.304 to 58.213 kg NO3-N ha−1 yr−1 comparing present versus future conditions. The overall nitrogen balance of the ensemble simulations reveals a mean nitrogen loss of 4.7 versus 5.7 kg-N ha-1 yr-1 comparing present to future conditions.
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Status: final response (author comments only)
- RC1: 'Comment on egusphere-2025-5311', Anonymous Referee #1, 09 Mar 2026
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RC2: 'Comment on egusphere-2025-5311', Anonymous Referee #2, 18 Mar 2026
General evaluation:
This paper is of potential interest to the journal. The model landscapeDNDC was used to simulate future crop yield and carbon and nitrogen balances/fluxes over Greece, with input from a large number of GCM-RCM combinations for two different time slices and two different concentration pathways. While the study is interesting, it has some important limitations, which are discussed later in the paper but not when the model setup is introduced or in the results section. In my opinion, assumptions and limitations should be highlighted when introducing the model setup. Additionally, the paper does not provide all the necessary details about the model experiments. A few additional model simulations (e.g. for different irrigation scenarios) would significantly strengthen the paper. Finally, the introduction should be improved by providing a clearer explanation of the novel contribution of the work. The language used in the paper, especially in the introduction, should be improved. Overall, I recommend a major revision of the paper.
Main comments:
Introduction: The motivation for this work is not clear in the introduction. The review of the modelled impact of climate change on carbon and nitrogen budgets and fluxes in agro-ecosystems is rather limited. This should be extended. In fact, the discussion provides more background on this, and some of this material would be better placed in the introduction.
Section 2.2.1: How was management considered in the model spin-up? Management will have an important impact on the initial conditions, calling into question the assumption of equilibrium conditions at the beginning of the simulation.
The assumption that irrigation will remain constant in the future is unrealistic. Either irrigation will increase in response to lower precipitation and higher potential ET, or it will not increase due to limitations in irrigation. The timing of irrigation would also change. One possible solution is to make irrigation a model-internal function of simulated soil moisture content, for example by initiating irrigation when soil moisture decreases below the critical threshold. While the authors acknowledge the limitations of their approach to irrigation, their proposed solution is not convincing.
Section 2.3: It seems that land use and land cover change is constant for all time slices. This decision should be discussed directly in the text. The reasons for this assumption and its limitations should be made clear.
Section 3 contains mainly tables and time series plots summarising the results. It would be useful to include some maps showing the simulation results. For example, ammonia emissions, nitrate leaching and changes in carbon storage for different time slices.
Results: It would be good to discuss the results in more detail. For example, why is there a carbon loss under current conditions, despite the model spin-up having simulated an equilibrium state? In this context, it would be important to have detailed information on the model spin-up setup (management, time period, transient climate and CO₂ concentration, etc.).
Given the significant impact of farmer nitrogen input on the system, it would be important to simulate different scenarios. For example, under conditions of lower precipitation and lower yields, the input of organic and mineral nitrogen by farmers could also be reduced. While it is challenging to anticipate future changes, simulating at least two realistic scenarios would be helpful.
Detailed comments:
L30–L32: These years are inconsistent with those provided in the paper.
L129: Is this a complete meteorological input dataset? Does the model not require wind speed and humidity?
L172–L173: The relevance of these should be explained more clearly.
L224: It seems that Q25 and Q75 have been mixed up here.
Table 2: Remove the column showing percentage changes in temperature.
Figures 2, 7 and 8: increase the font size. The lines in the figures (e.g. yellow on a red background) are not very clear.
L262–L263: This description lacks information on the removal of carbon by surface water and erosion. Please mention all components.
L326: A brief explanation of the results would be helpful here, such as why NH₃ and N₂O emissions change.
L340: Were fluxes to open waters not mentioned before, or do you mean leaching to groundwater?
Figure 7 appears before Figure 6 in the paper.
L395–L401: Please state explicitly that these are modelled results.
L405–L406: This is incorrect. More irrigation is likely needed, but this has not been considered. One simulation scenario could have been to investigate the impact on yield if irrigation amounts do not increase. Another simulation scenario could have considered the impact on yield, carbon and nitrogen if irrigation is adapted.
L435: What is the role of increasing potential ET and other stressors, such as heat stress? It would be helpful if you could provide more information on the factors contributing to reduced yield, such as reduced precipitation and increased heat stress.
L480–L481: Do you mean leaching into groundwater?
Conclusions: see my general comments regarding the treatment of irrigation and the possibility of performing different simulation experiments for different fertilisation scenarios.
Language (not exhaustive):
L35-L36: rephrase sentence
Reformulate all highlights
L63: 2 x effects
L66: “etc.” Remove or add further examples.
L71-L72: reformulate sentence
L81: systematic model errors?
L87-L89: rephrase sentence
L90: reformulate sentence
L137: error message in text
L143-L144: rephrase sentence
L191-L192: clarify sentence
L226-L227: rephrase: “Data is shown in Figure (…)”
L249-L251: rephrase sentence
L369: rephrase sentence
L421-L422: sentence unclear to me.
L441: error message in text
L447: process description
L493: due to the
Citation: https://doi.org/10.5194/egusphere-2025-5311-RC2
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- 1
The paper addresses a novel and relevant scientific topic of carbon and nitrogen fluctuations under climate change in Greece. However, the scientific methods and assumptions are not clearly outlined, there are several shortcomings, such as inadequacies in the presentation of the methodology; the description of experiments and calculations are insufficiently complete and precise to allow their reproduction by fellow scientists (traceability of results). The results are not sufficient to support the interpretations and conclusions, so that the conclusions cannot be retraced. Therefore, manuscript is not ready for publication.
The manuscript struggles to convey in clear language the scientific methodology and discuss robust results. The study is difficult to read primarily due to unclear methodological descriptions and a lack of several important details. A scientific manuscript also has the purpose to document results so that they are reproducible, however the inconsistencies and lack of attention to details leaves me wondering if all of the co-authors have proof-read the paper before submission.
The manuscript deals with C and N balances. As such I would expect a clear and prominent description of both formulae providing the inputs and outputs of the respective balances that the model deals with, and which are furthermore presented and discussed in the manuscript. Any indication of the inputs and outputs are currently lacking.
As well, not all readers are familiar with a waterfall diagram. An explanation of how to interpret such a diagram would be very useful. E.g. what are the start and end points? Do the gaps or lines correspond to anything?
As a reviewer, it is not my job to correct the wording or English syntax, so I shall omit undertaking these corrections and focus more on the content.
The title does not clearly reflect the contents of the paper, since about a third to one half of the paper deals with carbon results, but the word carbon does not appear in the title.
The abstract (particularly from L 31 onwards) needs to be reworded to reflect the results and clarify several issues mentioned below. Several sentences are not clearly phrased. What is the spatial unit examined in the study, because 0.25 degree is stated, yet the results are presented in ha-1 yr-1, why is this so? Be more specific when stating “arable production” as I believe this refers to the crop yields in terms of C in the biomass. What does soil C decrease? Which gases are emitted? Why are 2 values given for the gaseous emissions, what do these refer to? Etc.
The highlights require reworking. The first two points are related to climate scenarios, not to the core results of the study. The third point is not clear (see above comment pertaining to abstract). Does the 4th point refer to overall total C, or just biomass C, or just soil C?
The graphical abstract is not a “stand alone” figure, as the parameter names (y axis) may not be known to all readers. The number in the top left 5.7 kg N ha-1 yr-1 requires explanation. The inputs and the outputs of the N balance should be clearly marked or labelled.
In the introduction, the first part L 60-83 is too broad and does not add much new information. I would expect a more focused look at national studies of national N inventories, such as by Fan et al. 2020 and Strenge et al., 2023. A look at the main sources and sinks of N and C, and how these are affected by climate change is relevant to this study.
The research questions on L 101-108 are not formulated as research questions, but rather as bullet point statements.
The description of the Landscape DNDC model L 112-138 must include the spatial and temporal resolution at which it was set up. What was the input data used to set up the model including the time periods. L 128 states “daily or hourly climate variables”, but which was used in the study? All of the above is important information, as it lends credibility and rigor to the methodology. Thus, referring to Hass et al., 2013 is not sufficient, in my opinion.
L 151- 162: briefly describe the level of spatial resolution of the input data. What management data specifically was used as input? Tillage, plant residues, seeding and harvesting dates, fertilizer application and type? Was the same crop rotation in Hass et al., 2022 used for Greece and does this make sense to transpose the cropping systems to Greece?
L 153 states that 15 years were used for the warm up period (1990-2005). This contradicts L 31 of the abstract (10 years warm up period).
L 187-199 this section is very unclear. E.g. the year 2099 is stated, which contradicts several other parts of the study that state the simulations were carried out to the year 2100. L 195 mentions “spatial and temporal means are assumed” but what does this mean? Also, “these statistics” are mentioned, but which statistics are meant?
-L 208: describe which statistical analysis were carried out
I am missing a section at the beginning of the Results section on the calibration and validation of the model Landscape DNDC. How robust is this model? What was the observed data used to calibrate and validate the model (SOC, N), and which spatial resolution and time period was examined? How was the model calibrated and validated, with which method? What was the objective function used? etc…
- L 223-4: is it standard to use Q25 and Q75 in the text? Would be nice to introduce the meaning first, presumably it refers to quantile?
L 227-8: why is “a systematic decrease expected under both RCPs”? this seems to pre-empt the results
Furthermore, generally in the manuscript a description of the main crops grown in Greece are missing. Which crops are being examined in the study mainly? And what are typical management practices that are being examined and discussed in this manuscript?
Section 3.2 (L 248 -) needs to be reworked. It is not clear which response is meant. Is there is figure of these results? What is meant by “arable production”? Is it the C content of the biomass specifically?
It is not clear why the C decreases over the future period (also shown in Fig 2). This is presumably a decrease in yields. Why do they decrease? Looking at Fig 3 it is also not clear how the decrease is reflected in this figure 3?
I also suggest to move Section 3.3 before Section 3.2, so that the authors state the main C processes and then focus on the results of C in the biomass.
The discussion has repetition which can be omitted, see L395-401. The studies mentioned e.g. L501, are these measured or modelled N2O emissions?
L 466 - The whole country of Greece is lumped into one basket when discussing soil C loss rates. How useful is this? It would be more appropriate to have nuanced and land-use specific results discussed here. How comparable is Greece with the study from Hass et al., 2022, if the climate and soils are different between the studies?
I am missing a section in the uncertainties of the study, e.g. input data, spatial resolution, calibration and validation process and data. Interpretation and comparability with measured data.
Avoid writing bullet points in the conclusion.
The manuscript could greatly benefit from an English proof-reading service. Here are some examples of unclear scientific findings: L 320-323: „For the future time slice, we notice stronger differences in gaseous out-fluxes as N2O emissions under RCP4.5 of 0.476 (mean and median) versus 0.453 or 0.457 kg N2O–N ha−1 yr−1 under RCP8.5. N2 emissions show a decline in the future, comparing under RCP4.5 of 4.252 or 4.354 kg N2–N ha−1 yr−1 versus 3.377 or 3.171 kg N2–N ha−1 yr−1 under RCP8.5.” The values presented are not clearly attributable to what they are referring to; the mean or the median, or both? What about the RCP scenario) Also, the use of the preposition “or” is very confusing.
Another example: L 309-311, “Nitrogen deposition from atmospheric sources contributed by 5.68 kg N ha−1 yr−1 on croplands (see Table 5 and Figure 5), while synthetic nitrogen fertilization was 100.88 kg N ha-1 yr-1 and organic nitrogen fertilization was 19.89 kg N ha-1 yr-1 across both scenarios and all years and rotations.” I would expect to read the word “average” at least once in this description.
The use of the “C balance” and “N balance” throughout the document (e.g. in figure titles) is misleading. These results do not show the “balance” but rather selected components of the cycles.
All the captions of the figures should be reworded to reflect in detail the contents of the figures and explain them, so that they are “stand alone” figures.
The journal has high standards, which in my opinion are simply not met in this manuscript.
References
Fan, X., Worrall, F., Baldini, L.M., Burt, T.P., 2020. A spatial total nitrogen budget for Great Britain. Sci. Total Environ. 728, 138864 https://doi.org/10.1016/j. scitotenv.2020.138864.
Strenge E, Zoboli O, Mehdi-Schulz B, Parajka J, Schönhart M, Krampe J and Zessner M 2023 Regional nitrogen budgets of agricultural production systems in Austria constrained by natural boundary conditions J. Environ. Manage. 347 119023 https://doi.org/10.1016/j.jenvman.2023.119023