Representation of the nitrogen cycle and its coupling with the carbon cycle in ISBA (SURFEX v9) the land surface model: evaluation using two Free-Air CO 2 Enrichment experiment sites
Abstract
Nitrogen (N) is a critical nutrient, that controls photosynthesis and decomposition processes. It is important to include the N cycle in the land component of climate models to improve the exchange fluxes of CO 2 between land and atmosphere. We present here the implementation of the N cycle in the CNRM land surface model, namely ISBA. We evaluate the model on two Free-Air Enrichment (FACE), experiments sites: Duke and Oak Ridge. In particular, the response to elevated CO 2 is studied. We compare the reference version without the N cycle (C) and the new version in which it is included (CN). A comparison to a multi model analysis shows encouraging results, since the computed NPP and N assimilation flux fall in the inter model range. The CN version performs better than the C version for NPP. Next, we focus on the carbon cycle by comparing simulation results to observations. The CN version improves the carbon stocks, largely overestimated by the C version. In particular, at elevated CO 2 , in the CN version, photosynthesis is downregulated by the N limitation. This yields a reduction of C accumulation in soil and biomass in comparison to the C version. In the literature, diverging strategies are observed to overcome N limitation. The model reproduces well the main features but fails to represent some sites characteristics. Finally, a detailed analysis of the simulated N dynamics is presented.
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BibTeX
@article{decayeux2026representation,
title = {{Representation of the nitrogen cycle and its coupling with the carbon cycle in ISBA (SURFEX v9) the land surface model: evaluation using two Free-Air CO 2 Enrichment experiment sites}},
author = {Jeanne Decayeux and Bertrand Decharme and Romain Darnajoux and Christine Delire},
journal = {Geoscientific Model Development},
year = {2026},
month = aug,
doi = {10.5194/gmd-19-7787-2026},
url = {https://hal.science/hal-05749063v1},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Representation of the nitrogen cycle and its coupling with the carbon cycle in ISBA (SURFEX v9) the land surface model: evaluation using two Free-Air CO 2 Enrichment experiment sites
AU - Jeanne Decayeux
AU - Bertrand Decharme
AU - Romain Darnajoux
AU - Christine Delire
PY - 2026
DA - 2026/08/21
JO - Geoscientific Model Development
DO - 10.5194/gmd-19-7787-2026
UR - https://hal.science/hal-05749063v1
AB - Nitrogen (N) is a critical nutrient, that controls photosynthesis and decomposition processes. It is important to include the N cycle in the land component of climate models to improve the exchange fluxes of CO 2 between land and atmosphere. We present here the implementation of the N cycle in the CNRM land surface model, namely ISBA. We evaluate the model on two Free-Air Enrichment (FACE), experiments sites: Duke and Oak Ridge. In particular, the response to elevated CO 2 is studied. We compare the reference version without the N cycle (C) and the new version in which it is included (CN). A comparison to a multi model analysis shows encouraging results, since the computed NPP and N assimilation flux fall in the inter model range. The CN version performs better than the C version for NPP. Next, we focus on the carbon cycle by comparing simulation results to observations. The CN version improves the carbon stocks, largely overestimated by the C version. In particular, at elevated CO 2 , in the CN version, photosynthesis is downregulated by the N limitation. This yields a reduction of C accumulation in soil and biomass in comparison to the C version. In the literature, diverging strategies are observed to overcome N limitation. The model reproduces well the main features but fails to represent some sites characteristics. Finally, a detailed analysis of the simulated N dynamics is presented.
SN - 1991-9603
SN - 1991-959X
ER -