Community processes as emergent properties: Modelling multilevel interaction in small mammals communities

Simulations have been executed for two different scenarios. The Bornhöved scenario simulating the situation of a Northern German rodent community in a beech forest represented bottom-up effects of mast events on population dynamics. The Scandinavian scenario which depicted the most important actors of these oscillating rodent communities, gave new insights into the processes causing the sudden decline of rodent populations. Both, lack of resources and predation, contributed to about 90% of mortality, but no pattern could be found when relating either cause with the properties of the respective cycle. Bottom up and top down control vary unpredictably and chaotically in the model. These results may explain considerable parts of contradicting empirical findings.