Spatiotemporal Scales of Non-equilibrium Community Dynamics: a Methodological Challenge

mechanisms that prevent competitive exclusion either by the increased mortality of the competitive superiors [IDH] or by the permanent rearrangement of the competitive dominance hierarchy [GCC]. Very strong disturbances and extreme environmental changes result in communities of low diversity. Low-level (infrequent,low intensity or small spatial scale) occurrences of these mechanisms cannot prevent competitive exclusions and also lead to low diversity. The trivial expectation, common in both hypotheses, is that there should be some ‘intermediate level’ of these mechanisms that would produce the highest diversity. However, the present versions of IDH and GCC are unable to define, specify, and measure “intermediacy”. All previous contributors emphasized that population parameters (generation time, growth rates, competitive abilities) and community parameters (successional states) together with the parameters of disturbance regime or environmental fluctuations are important to predict diversity. However, neither have clear quantitative predictions been formulated nor have clear methodological recipes been proposed to define what to measure and at which scales. Introduction