Hi Ayn, I am aware of folks at USFS Regions 1, 6, and 3 using FVS to “calibrate” their STSMs. A key aspect of this process is to include the state resolution and classification in order to relate state changes from FVS to ST-Sim. These folks have developed a state class classification based on variables such as diameter, number of canopy stories, and percent canopy cover that can be related back to transitions in ST-Sim when certain thresholds are crossed for these variables. I think “calibration” is a more appropriate word for this rather than “validation”.
Similarly others have used retrospective analyses over time periods with known landscape conditions to “calibrate” transition rates in their models such that the projected landscape over the historic time period matches observed changes on the real landscape, for example Frid et al. 2013.
Oreskes et al. 1994 provide a thoughtful perspective on whether it is ever really possible to validate numerical models.