Testing the application of process-based forest growth model PREBAS to uneven-aged forests in Finland

•The process-based model PREBAS was applied to uneven-aged forests.•Introducing DBH size classes helps to model the photosynthesis in different canopy layers.•The PREBAS model with DBH size classes can improve model predictions.•Reineke mortality model appeared to be more appropriate for even-aged forests.•The introduced mortality model presented better competition environment of trees in uneven-aged forests.