- 1Karlsruhe Institute of Technology, Institute of Meteorology and Climate Research, Atmospheric Environmental Research (IMK-IFU), Terrestrial Bio-Geo-Chemistry, (carolin.boos@kit.edu)
- 2University of Bonn, Institute of Crop Science and Resource Conservation (INRES), Katzenburgweg 5, 53115 Bonn, Germany
- 3Chair of Soil Physics, Bayreuth Center of Ecology and Environmental Research (BayCEER), University of Bayreuth, Bayreuth, Germany
- 4Institute of Soil Science and Land Evaluation, University of Hohenheim, 70559 78 Stuttgart, Germany
Plants are the main connection between soil and atmosphere. Below ground, nitrogen, carbon, and water fluxes are mediated by roots, which therefore strongly influence nitrogen, carbon, and water distributions throughout the soil profile and impact, for instance, if conditions favorable for denitrification occur or not. However, the representation of roots in biogeochemical models is often strongly simplified, allowing only for a static prescribed root development. Further, the root system is normally not taken into account during model calibration, due to a lack of measurements. This disregard of roots prevents model veracity. In this study, we evaluate three model settings of the biogeochemical model framework LandscapeDNDC and compare them to site measurements of winter wheat and maize on a stony and a silty soil to illuminate and quantify these shortcomings. As a baseline, the model is calibrated regarding above ground parameters and measurements only. These results are compared to calibrations on above and below ground parameters and measurements with two different root models. One static root model and one dynamic root model proposed by Jones et al. in 1991. The calibrated settings yield overall comparable qualities of fit for the above ground properties. As expected, the root depth and the root length density are better represent after calibration. The best qualities of fit in the validation are relative root mean square errors (coefficients of determination) of 0.76 (0.36) and 0.39 (0.86) for the root length density and root depth, respectively. At last, for the best-fit model run of each setting, the nitrogen balance is analysed. On the stony soil, the simulated nitrate leaching from the baseline is 80 % smaller than in a setting where the roots were properly calibrated. In line, the plant nitrogen uptake was on average 40 kgNha-1 bigger in the baseline compared to the other settings. These large impacts on the nitrogen cycle illustrate the need for joined measurements of roots and nitrogen fluxes.
How to cite: Boos, C., Nguyen, T. H., Cai, G., Morandage, S., Kraus, D., Haas, E., and Kiese, R.: Root simulations in a biogeochemical model and impacts on nitrogen fluxes, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-9480, https://doi.org/10.5194/egusphere-egu25-9480, 2025.
