Evaluating individual-tree growth simulators in terms of natural stand dynamics : Dissertation, University of Natural Resources and Applied Life Sciences, Institute of Forest Growth

Wien

Universität für Bodenkultur - BOKU

2010

182 S.

Monographie

16564

169958

This thesis aimed to evaluate the European individual-tree growth Simulators BWINPro, MOSES, SILVA and PrognAus in terms of the simulated long-term development of species composition and the simulated sequence of stand development stages under the Option of no management. Data of the Austrian NationalForest Inventory was used to develop Statistical modeis to identify stand development stages by means of stand characteristics. Then, in order to assure that the program source code does not contain constraints to avoid eventually implausible Simulation results, the Simulators have been reprogrammed. Implementing a regeneration model into SILVA could not be achieved, and consequently this Simulator could not be used for further investigations. The other 3 Simulators were used to estimate the humanly uninfluenced development of different sites over a period ot 2500 years. PrognAus simulated distinctly different steady-state species compositions for different sites. Comparisons with the species-compositions expected for the different potential natural Vegetation types by experts in Vegetation science showed ;hat PrognAus achieved good results for sites where Norway spruce and European beech are expected to be predominant, the major part of Austrian forest sites. However. PrognAus showed weaknesses in simulating forest types dominated by oak or pine species. Simulations using BWINPro always resulted in pure beech forests, independent of site. Concerning the simulated sequence of stand development stages both PrognAus and BWINPro achieved plausible results. However, both simulaors showed weaknesses in reproducing stages whose main feature is the existence of regeneration; this is due to the fact that they use a diameter threshold and thus lulted in imnlansiVilv Rman «fand volumes. High stand densities cause very large iilted in implausibly small stand volumes. Higii stand densities cause very large competition indices for the individual trees and thus very low growth rates.