SPATIOTEMPORAL SCALES OF NONEQUILIBRIUM COMMUNITY DYNAMICS - A METHODOLOGICAL CHALLENGE

The Intermediate Disturbance Hypothesis [IDH] and the Gradual Climate Change Hypothesis [GCC] offer intuitively appealing, verbal non-equili brium explanations to species coexistence in competitive communities, but so far they lack a solid theoretical background and a proper exper imental methodology. To make them testable and comparable on a solid m ethodological basis, they should be formulated as well-defined non-equ ilibrium community dynamical models. We suggest that this is possible, if explicit assumptions on the spatiotemporal structure of the enviro nment and the pattern-generating mechanisms of the species assemblage in question are given. In the framework of a non-spatial population dy namical model we show that disturbance and climate change effects can be safely distinguished, and the ''intermediate'' level of external ef fects leading to maximum community diversity can be quantified. Based on the information statistical analysis of field data and simulation r esults, we explain why it is necessary to consider simultaneously the spatiotemporal patterns of the vegetation, the abiotic environment and the disturbances in order to predict the consequences of external eff ects regarding community diversity.