Modelling aspects of forest decline in Germany: I. Theoretical aspects and cause-effect relationships

In 1993 the German Federal Environmental Agency initiated a project to evaluate the forest decline research of the period 1982–1992 in Germany. The development of the symptoms of the ‘new type of forest decline’ is the effect of direct and indirect impacts on trees and ecosystems. The cause-effect relationships concerning the soil/plant interface are discussed shortly. One aim of the project was the integration of quantitative and qualitative research results in a simulation model. According to the manifold site conditions in Germany and possible combinations of direct and indirect stress factors a flexible model structure with a modular construction was chosen. The modules can operate individually or together. This enables the user to test hypotheses, or calculate scenarios. Thus, the model acts as a link between empiricism and theory. The practical and theoretical constraints and problem solutions are discussed. In a second paper the model performance and its applicability range are shown [1, this volume].