WP5 has 3 steps:

WP5-1 Improvement of CERES-NOE, CN-Vsoil using effective functions and/or simple models of WP4

Raia Massad, Patricia Garnier, Catherine HénaultJoel Daroussin JR de Dreuzy, 6 Months IE

CERES and CN-Vsoil models simulate the decomposition of organic matter, nitrogen dynamics and N₂O fluxes (Lehuger et al. 2009) in soil. All these models use macroscopic functions that alter the microbial dynamics such as a function of humidity, temperature, availability of nitrogen, and an empirical function for contact between microbial biomass and organic matter (see Garnier et al., 2003, Moyano et al., 2013) but they do not consider micro-heterogenity descriptors. These models will be modified to take into account the influence of the microscopic heterogeneity in the soil. The outputs of WP4, i.e. effective parameters or functions and/or simple compartment models able to consider the microscopic distribution from descriptors, will be used for this and will lead to changes in existing functions, to the addition of new functions, ,or even to changes in the structure of the traditional models. This step will be done in close collaboration with the actors of WP4 by a contractual IE (6 months, located in Orleans)

WP5 -2 Test of the improved models in field

Raia Massad, Patricia Laville, Patricia Garnier, Catherine Hénault, Claire Chenu, 6 months of Phd 1

A comparison of initial models with improved ones will be carried out to test the improvements against experimental data. This comparison will be done using existing databases collected on different field experiments, with soils of contrasting textures and structures: 

-           For loamy soils (from 60 to 75% silt) we will have access to results obtained on the experimental field ICOS of Grignon (Laville et al., 2011, Loubet et al., 2011), and the landscape site (INGOS-OS²) located in Center Region (Gu et al., 2011 ; 2014 ; Grossel et al., 2014) which is used in the ANR-Escapade project (http://www.n-escapade.fr/Sites/Site-OS2). In these field sites, GHG emissions (CO₂ and N²O) have been registered periodically using accumulation chambers. All other field data are also available (climatic data, soil properties,…). Furthermore, the experimental site of La Cage, at Versailles, from which most soil samples of our project will come, has been equipped in 2014 with accumulation chambers to record the emissions of CO₂ and N₂O, within the PhD project of B. Autret (P.I B. Mary , INRA). A specific collaboration is being discussed to test our models against their field data, as much information will be available from this project, regarding the microstructural components of the soils and the spatial variability of CO₂ and NO² emissions at the aggregate to core scale (see WP1). Both conventional tilled and no tillage with permanent plant coverage plots will be considered, in order to take advantage of the observed  differences in soil structure and soil organic C content (Juarez 2013).

-           For sandy soils (from 75 to 85%): The experimental site Ardon located in Orléans (Center Region), cultivated with soybeans, has been recently equipped with chambers to measure N₂O. All other field data will be also available (climatic data, soil properties,…).

Deliverables:

-           Field scale models of soil CO₂ and N₂O emissions able to consider µ-heterogeneity of soils at the field scale;

-           Test of these “improved” soil models with experimental field data.