Adaptation of a soil heterotrophic respiration model to an agricultural soil.

This work aimed at adapting a model of soil heterotrophic respiration to an agricultural soil situated in the Hesbaye region (Belgium) and cultivated with a sugar beet / winter wheat / potato/ winter wheat rotation. This model would be integrated as a sub routine in a larger model describing soil respiration and soil carbon content evolution in crops and that will include autotrophic respiration and CO2 diffusion in soil. The present model is run at a daily time step and at the ecosystem spatial scale and is derived from the CENTURY model. Model parameterisation was performed on the basis of literature survey and of data collected at the Carboeurope agricultural site of Lonzée. Soil characteristics were determined on the basis of analyses performed on loamy soils, typical of the Hesbaye region. Driving variables (meteorological variables and litter input) were obtained during a 4 year measurement campaign performed at the Lonzée experimental site. Biochemical parameters for wheat, potato and sugar beet crops were collected from literature. However, a large parameter variability was noticed as well as a lack of information concerning sugar beet and potato. A sensitivity analysis was performed in order to classify the different parameters in terms of their impact on the respiration rate and carbon contents of each pool. It showed that the most important parameters were those controlling the temperature response, the litter input and its nitrogen and lignin content. The sensitivity analysis also showed differences in parameter impact between short and long term, notably because of pool stabilisation dynamics and crop residue types. This analysis allowed defining the further experiments that need to be developed in order to improve model adjustment on experimental data.