A simplified gross primary production and evapotranspiration model for boreal coniferous forests – is a generic calibration sufficient?
F. Minunno1, M. Peltoniemi2, S. Launiainen2, M. Aurela3, A. Lindroth4, A. Lohila3, I. Mammarella5, K. Minkkinen1, and A. Mäkelä11Department of Forest Sciences, University of Helsinki, P.O. Box 27, Helsinki 00014, Finland 2Natural Resources Institute Finland (Luke), Jokiniemenkuja 1, 01301 Vantaa, Finland 3Finnish Meteorological Institute, 00560 Helsinki, Finland 4Lund University, Department of Physical Geography and Ecosystem Science, Lund, Sweden 5Department of Physics, P.O. Box 48, 00014, University of Helsinki, Finland
Received: 16 May 2015 – Accepted for review: 08 Jun 2015 – Discussion started: 02 Jul 2015
Abstract. The problem of model complexity has been lively debated in environmental sciences as well as in the forest modelling community. Simple models are less input demanding and their calibration involves a lower number of parameters, but they might be suitable only at local scale.
In this work we calibrated a simplified ecosystem process model (PRELES) to data from multiple sites and we tested if PRELES can be used at regional scale to estimate the carbon and water fluxes of Boreal conifer forests. We compared a multi-site (M-S) with site-specific (S-S) calibrations. Model calibrations and evaluations were carried out by the means of the Bayesian method; Bayesian calibration (BC) and Bayesian model comparison (BMC) were used to quantify the uncertainty in model parameters and model structure. To evaluate model performances BMC results were combined with more classical analysis of model-data mismatch (M-DM). Evapotranspiration (ET) and gross primary production (GPP) measurements collected in 10 sites of Finland and Sweden were used in the study.
Calibration results showed that similar estimates were obtained for the parameters at which model outputs are most sensitive. No significant differences were encountered in the predictions of the multi-site and site-specific versions of PRELES with exception of a site with agricultural history (Alkkia).
Although PRELES predicted GPP better than evapotranspiration, we concluded that the model can be reliably used at regional scale to simulate carbon and water fluxes of Boreal forests.
Our analyses underlined also the importance of using long and carefully collected flux datasets in model calibration. In fact, even a single site can provide model calibrations that can be applied at a wider spatial scale, since it covers a wide range of variability in climatic conditions.
Minunno, F., Peltoniemi, M., Launiainen, S., Aurela, M., Lindroth, A., Lohila, A., Mammarella, I., Minkkinen, K., and Mäkelä, A.: A simplified gross primary production and evapotranspiration model for boreal coniferous forests – is a generic calibration sufficient?, Geosci. Model Dev. Discuss., 8, 5089-5137, doi:10.5194/gmdd-8-5089-2015, 2015.