PARENT SESSION
Oral Session #74: Spatial Ecology: Models and Methods. Presiding: C. Loehle.
Friday, August 10, 2001. 8:00 AM to 11:30 AM. Hall of Ideas E.
Cluster size distributions: signatures of self-organization in spatial ecologies.
ROY, MANOJIT1, PASCUAL, MERCEDES1, FLIERL, GLENN2, 1 2
ABSTRACT- We show that two different individual-based predator-prey models exhibit similar power-law scalings in the geometry and distribution of prey clusters. Furthermore, in the coexistence regime these patterns are robust: the exponent of the cluster size distribution and the associated Korcak exponent characterizing patchiness, depend only weakly on the parameters of the systems. These distributions, in particular the values of the exponents, are quite close to those reported in the literature for systems associated with self-organized criticality (SOC), such as those for forest-fire and related epidemics models in small populations; however, the typical assumptions of SOC need not apply. Our results demonstrate that power-law decay in cluster size distributions and the specific values of their exponents are not restricted to particular ecological systems for antagonistic interactions. The patterns are characteristic of intrinsic processes of growth and inhibition in space, such as those in predator-prey and disturbance-recovery dynamics. Inversions of these patterns, that is, scalings with positive slope as described for plankton distributions, require spatial forcing by the external environment.
KEY WORDS: individual-based predator-prey models, cluster size distribution, power-law scaling, self-organization