Improving the Fagacees growth model with an expanded common beech (Fagus sylvatica L.) data series from France and Germany

Key message The Fagacees growth model was originally designed for application in the Northern half of France. It is a robust model with potential applicability to a larger area, though this potential has not yet been verified. We added new data to the original parameterization data set and our results show that the Fagacees formalism can be generalized. Context The Fagacees growth and yield model was designed for the management of pure even-aged stands of European beech and served as a prototype to build models for other tree species. Aims The objective of this study was to improve the growth components of the Fagacees model with additional data from North-Western France to South-Western Germany. Material and methods Our model was calibrated on several forest inventory data sets. The first one (F) is the original data set that was used to elaborate the equations in the Fagacees model. The second one (F+) is the original data set extended with additional measurements on the same sites and on new sites in Northern France. The third (G) adds complementary data from a forest network in Southwestern Germany. The last one (A) is the aggregate of all these data sets. Results Fitting the original model equations on the extended F+ dataset led us to modify the equation for stand basal area increment. This new equation also fit the German dataset well. The other equations could be applied to all datasets, some with the same parameter values and some after recalibrating according to the dataset. Conclusion We conclude that the general form of the model's equations is appropriate for application to other regions, but that a recalibration of the equations is preferable in order to reflect local conditions. The advantage of our approach is that fewer data are required to recalibrate an existing equation than to establish an entirely new one.

Automated summary

The Fagacees growth model, originally designed for the Northern half of France, shows potential applicability to a larger area. By adding new data from North-Western France to South-Western Germany, the model's equations were found to be suitable for application in other regions with a recalibration needed to reflect local conditions.