A generic primary producer model for use in ecosystem simulation

This article is a description of a primary producer (plant) model that has been developed as part of a larger ecosystem modelling project in the field of biosystems engineering. Plants in the ecosystem are represented with a generic model that can be configured to represent many different types of species, including herbs, bushes and trees. Each plant, or small collection of plants, is represented by a unique “object” with attributes and functions. Population level dynamics are therefore governed by and emerge from object-level rules that describe processes such as growth and reproduction. The plant objects are distributed over a spatially explicit terrain, and their behaviour is driven by irregular climatic forcing functions. The plant canopy is modelled with three layers of vertical differentiation, which affects inter-species competition for available radiant energy. In addition to competing with other plants for essential nutrients, sunlight and water, the plant objects may also be subject to predation by herbivores. The performance of the plant model is demonstrated with simulations based on ecosystems configured with small collections of species distributed about a 500×500 m2 terrain. Results show this modelling approach to be effective in depicting phenomena at the individual, population, and ecosystem-levels, including effects of herbivory and inter-species competition on plant growth, patterns of plant population dynamics and spatial distribution, and total system biomass.