Calibration and validation of a semi-empirical flux ecosystem model for coniferous forests in the Boreal region

• The applicability of a forest flux ecosystem model to the Boreal region was tested.
• Eddy-covariance measurements from 10 sites were used to evaluate the model.
• We compared the performances of multi-site (M-S) vs site-specific (S-S) calibrations.
• M-S showed robust results and can be used for regional applications.
• Long and carefully collected flux dataset leads to better model performances.

Simple models are less input demanding and their calibration involves a lower number of parameters, however their general applicability to vast areas must be tested. We analysed if a simple ecosystem model (PRELES) can be applied to estimate carbon and water fluxes of Boreal forests at regional scale.Multi-site (M-S) and site-specific (S-S) calibrations were compared using evapotranspiration (ET) and gross primary production (GPP) measurements from 10 sites. The performances of M-S were similar to S-Ss except for a site with agricultural history. Although PRELES predicted GPP better than ET, we concluded that the model can be reliably used at regional scale to simulate carbon and water fluxes of Boreal forests.We further found that, in the calibration, the use of a long and carefully collected flux dataset from one site that covers a wide range of climate variability leads to better model performance in other sites as well.