Approaches for the restoration of forest ecosystems in northeastern Bavaria

The concept of restoration of ecosystems can be divided into three parts, depending on the ecological concept of disturbance and its expression at various hierarchical levels: (i) restoration of basic structural components, (ii) restoration of interactions among these components, and (iii) restoration of the entire ecosystem. Forest ecosystems in northeastern Bavaria show that structural components such as tree composition and soil solution have been altered to a large extent. Compared with the demands of potentially natural vegetation there is a great deal of evidence to suggest that without reconstruction of these structures and compartment conditions, restoration cannot be achieved. Nevertheless, this kind of restoration will not succeed if, in addition, restoration of the heavily changed processes between structural components is not carried out. The example of acid deposition and historical degradation in forest ecosystems demonstrates the driving forces of these changes in processes. In some mountainous regions of northeastern Bavaria, restoration will only be possible if acid deposition is reduced by nearly 100% (but some mitigation measures such as liming and fertilizing can support natural regeneration). In order to restore the entire ecosystem most effectively, both the structure and interrelation processes have to be evaluated. So-called rate-types of spruce-dominated ecosystems are very sensitive to acid deposition. Pool-types might be recharged by liming and fertilization and react in a time-delayed manner, which means that they are more elastic and probably easier to restore. Summarizing the situation in several forested areas of Central Europe, it is to be feared that: • - losses and changes of structure cannot simply be replaced or reconstructed any longer because • - essential processes and interactions have been changed. These could be partially compensated for, but • - ecosystems as a whole are exposed to a long-term and continual critical overloading from the higher level systems. The scale and speed of these changes serve to increase the gap between available knowledge and the planning of restoration measures. As such, restoration is no more than a mitigation process or a combatting of symptoms before it becomes restoration in the real sense of the word.