A generic, individual-based approach to modelling higher trophic levels in simulation of terrestrial ecosystems

In this article, a description is given of the manner in which higher trophic levels (animals) are represented in a generally configurable ecosystem model. The animals are modelled using an individual-based approach that is sufficiently generic to allow for the representation of organisms of different types of species via the specification of appropriate sets of parameter values. Animal behaviours and physiological functions are described with simple mechanistic rules that are derived from various assumptions about, for example, growth rates, metabolic requirements, digestion and assimilation of food, or gestation. The animals interact in a detailed, spatially explicit environment that consists of a terrain, an atmosphere, and various species of primary producers. The model has been implemented in simulation to explore population dynamics in multi-species ecosystems configured with two and three trophic levels. Sample simulation results are presented, together with a discussion of the effectiveness of the approach for the representation of animals in ecosystem modelling.