Community processes as emergent properties: Modelling multilevel interaction in small mammals communities
Authored by H Reuter
Date Published: 2005
DOI: 10.1016/j.ecolmodel.2005.02.011
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Abstract
Community interactions of small rodents have attracted the attention of
ecologists for many years due to their abrupt changes in population
numbers, their impact on the whole biocoenosis and also because of
immense damages to agricultural production and forestry. In particular, regularly oscillating rodent populations in Scandinavia have been
subject of discussions among theoretically and empirically working
ecologists for many decades. Spatial and temporal restrictions in
empirical work led to various attempts to model these dynamics to
understand large scale effects resulting from complex interactions in
variable cause-effect networks of the numerous involved system
components.
The presented individual-based model for the first time described small
rodent communities as a set of interacting autonomously acting agents
with a detailed life history and behavioural repertoire in a food-web
setup composed of three trophic levels (rodents, rodents food and
predators). It thus allowed to integrate all relevant factors accounting
for the dynamics of rodents which acted in a simulated environment
containing the spatial arrangement of habitats and seasonal changing
conditions. Due to the representation with interacting entities, the
dynamics on higher levels resulted in a self-organisation process as
emergent properties. This differentiation between the focal and the
operational level allowed to investigate processes interacting between
different integration levels and to adapt the model to different
scenarios easily as well as to specify it for a large range of rodents
species.
Simulations have been executed for two different scenarios. The
Bornhoved 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. (c) 2005 Elsevier B.V. All rights reserved.
Tags
field vole
Trophic interactions
Density-dependence
Vole microtus-agrestis
Weasel mustela-nivalis
Population-cycles
Small
rodents
Clethrionomys-glareolus
Fluctuating populations
Parameterized models