A decision support system model is described to advise nature park managers. It applies dynamic modelling techniques to relate abiotic characteristics of a site over time to species that can be found. For a desired vegetation type it determines how such abiotic factors are to be changed in order to obtain the desired change in the vegetation after some time. The system takes into account an ecological model of the temporal dynamics of species, interspecies interactions, and abiotic factors. Applying model-based reasoning and dynamical systems methods to this ecological model, decision options on abiotic conditions are determined in order to obtain desired vegetation types.