In:
Ecology, Wiley, Vol. 100, No. 5 ( 2019-05)
Abstract:
The isotopic composition (ic) of soil nitrogen (N) and, more recently, the intramolecular distribution of 15 N in the N 2 O molecule (site preference, SP) are powerful instruments to identify dominant N turnover processes, and to attribute N 2 O emissions to their source processes. Despite the process information contained in the ic of N species and the associated potential for model validation, the implementation of isotopes in ecosystem models has lagged behind. To foster the validation of ecosystem models based on the ic of N species, we developed the stable isotope model for nutrient cycles (SIMONE). SIMONE uses fluxes between ecosystem N pools (soil organic N, mineral N, plants, microbes) calculated by biogeochemical models, and literature isotope effects for these processes to calculate the ic of N species. Here, we present the concept of SIMONE, apply it to simulations of the biogeochemical model LandscapeDNDC, and assess the capability of 15 N‐N 2 O and, to our knowledge for the first time, SP, to constrain simulated N fluxes by LandscapeDNDC. LandscapeDNDC successfully simulated N 2 O emission, soil nitrate, and ammonium, as well as soil environmental conditions of an intensively managed grassland site in Switzerland. Accordingly, the dynamics of 15 N‐N 2 O and SP of soil N 2 O fluxes as simulated by SIMONE agreed well with measurements, though 15 N‐N 2 O was on average underestimated and SP overestimated (root‐mean‐square error [RMSE] of 8.4‰ and 7.3‰, respectively). Although 15 N‐N 2 O could not constrain the N cycling process descriptions of LandscapeDNDC, the overestimation of SP indicated an overestimation of simulated nitrification rates by 10–59% at low water content, suggesting the revision of the corresponding model parameterization. Our findings show that N isotope modeling in combination with only recently available high‐ frequency measurements of the N 2 O ic are promising tools to identify and address weaknesses in N cycling of ecosystem models. This will finally contribute to augmenting the development of model‐based strategies for mitigating N pollution.
Type of Medium:
Online Resource
ISSN:
0012-9658
,
1939-9170
DOI:
10.1002/ecy.2019.100.issue-5
Language:
English
Publisher:
Wiley
Publication Date:
2019
detail.hit.zdb_id:
1797-8
detail.hit.zdb_id:
2010140-5
SSG:
12
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