Flexible and fast, computer simulations now play an important role in the study of ecology. This book gives a complete account of one such simulation, the Hurley Pasture Model, a dynamic, deterministic, mechanistic model for grassland, developed by the author and his colleagues over the last twenty years. The book presents the rationale and theoretical elements of this type of model, followed by an overview of the Hurley grassland simulator and the derivation and construction of its plant, animal, soil and litter, water, and environment and management components. The model is then evaluated by a series of long- and short-term dynamic simulations and steady state responses, which demonstrate how predictions can be made about the effects of, for example, climate change or particular regimes of fertilizer application, grazing or cutting. This book will be of great value to grassland agronomists and modelers, crop physiologists and plant ecologists, and to students of ecology as a case study of a plant ecosystem model. It will also be of interest to other ecologists and environmental scientists pursuing computer modeling and its applications.