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A Grasshopper Model for a Grassland Ecosystem

Rodell, Charles F.
Ecology 1977 v.58 no.2 pp. 227-245
age structure, air temperature, carbon, death, diet, ecosystems, energy flow, equations, feces, grasshoppers, grasslands, herbivores, models, population dynamics, predation
A state variable, process—oriented model is presented that considers the effect of grasshoppers on a grassland ecosystem. The model considers that interactions with producer, decomposer, and other consumer components via the mechanistically implemented flow of carbon through the system. The primary driving variables that influence the grasshopper model are air temperature and precipitation. Grassphopper have a direct effect on producers through diet selection, herbivory, and damage as the result of feeding. Interactions with the decomposers are the result of death and feces production. Grasshoppers interact with other consumers as the result of competition for food and predation on the grasshooper population. The major objectives addressed in the model are estimates of the grasshopper population dynamics, the effects grasshoppers have on the total grassland system, and the amount of energy flow through the grasshopper population. The age structure of the grasshopper population is considered only where information exists to indicate that age groups are functionally different and can be represented within the resolution of the model. The model is formulated in first—order difference equations in the simulation language SIMCOMP. Simulation results of the model are presented and discussed.