PREBAS is a forest model system developed at the University of Helsinki, with the objective of making future projections of a given forest stand with known initial state under alternative management options. Currently, it consists of three modules, PRELES, CROBAS and YASSO07. In order to allow for applications over large geographical areas accounting for observed forest properties and management options, the models were constructed to be as simple as possible in structure, yet based on biologically sound assumptions. The models are based on carbon fluxes and stocks between the atmosphere and the forest ecosystem. The system is modular, such that modules can be used either independently or linked, where the carbon fluxes determine the linkages. PRELES (Peltoniemi et al. 2015, Minunno et al. 2016) estimates canopy photosynthesis and evapotranspiration from daily environmental drivers and stand properties. CROBAS (Mäkelä 1997, Valentine and Mäkelä 2005) is a stand growth model based on carbon acquisition and allocation in trees. The models have been further combined with the Finnish soil carbon model YASSO07 (Tuomi et al. 2009). All modules have been independently tested and calibrated against data from eddy flux stations, forest experiments and inventories, and soil processes.
