Modelling N2O emission from a forest upland soil: A procedure for an automatic calibration of the biogeochemical model Forest-DNDC

During the last decade biogeochemical models such as DNDC or PnET-N-DNDC have been widely used to simulate gaseous emissions from soil. So far, no efforts have been made to automatically calibrate such biogeochemical models. The aim of this study was to demonstrate a procedure for an automatic calibration of the Forest-DNDC model. We linked Forest-DNDC with a computer code for universal inverse modelling (UCODE). The model was calibrated and validated for an upland soil (Endoskeletic Cambisol) on the basis of a 4-year field data set from the study site “Wildmooswald” (Black Forest, Germany). Our results show that the software linkage between Forest-DNDC and UCODE yields a useful tool for model calibration. The calibration markedly improved model performance for the periods 2001–2002 and 2003–2004 by reducing the error variance by up to a factor of two. For the period 2003–2004, the default simulation underestimated the measured mean daily N2O emission by 41%. After calibration the model performed much better. The calibrated simulation overestimated mean daily N2O emission only by 7%.