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Publication Date

1981

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A conceptual model was developed using a modified-state variable approach, which involved the recognition and suitable description of specific objectives, processes, and situations considered relevant to the simulation of ecosystem dynamics. Six primary ecosystem subsystems were selected: terrestrial abiotic, floral and fauna, aquatic abiotic and biotic, and topographic land use. These subsystems are embodied by a geographic structure defined as an ecological response unit (ERU). Subsystem characteristics of an ERU are considered homogenous, but between ER Us the characteristics may differ greatly. A set of ER Us may be arranged into any mosaic pattern, a quality that affords a unique response behavior to both the individual ERUs and the mosaic pattern. Discrete management events, such as controlled burning or livestock stocking, and continuous events, such as oil-shale mining, may be scheduled for a complex of ERUs. As the model operates "mechanistically," the results are tractable, and they provide a framework for interpretation and discussion among resource managers. A computer-based simulation model of the conceptual model, named An Ecosystem Simulation of Perturbations (AESOP), has been developed to provide resource managers with a methodology for analyzing the future consequences of multiple-use management scenarios. The computer model provides pseudoquantitative ecosystem responses as a consequence of various management strategies. AESOP allows a user to specify many types of scenarios involving both ecosystem characteristics and management practices, which may vary in location, timing, and magnitude. AESOP was programed in the general-purpose computer language PASCAL because of the superior data-typing and program­structuring capabilities of the language, which allow model flexibility not possible with most models reported in the ecological literature. AESOP closely imitates the conceptual model through data-structuring techniques and derived mathematical func­tions representing ecosystem relationships. The block structure of the computer program provides ease in understanding and evaluation by the user and change or interchange of simulation procedures. AESOP generates time-series data of the components and processes of the ERUs and indices of subsystem conditions. A separate analysis program summarizes the voluminous output into statistical tables and graphs. The model is currently being tested by evaluating ecosystem response to multiple-use resource management of the sagebrush­grass areas in northwestern Colorado. This region is unique in its richness of energy-producing resources, its abundance of wild herbivoJ"es, and its livestock and agricultural practices. Through analysis of the results from various management-policy scenario simulations, "hindsight" is available to the resource manager at the time of decision-making.

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Spatial Simulation Modeling as a Tool in Multiple-Use Management of Renewable-Resource Systems

A conceptual model was developed using a modified-state variable approach, which involved the recognition and suitable description of specific objectives, processes, and situations considered relevant to the simulation of ecosystem dynamics. Six primary ecosystem subsystems were selected: terrestrial abiotic, floral and fauna, aquatic abiotic and biotic, and topographic land use. These subsystems are embodied by a geographic structure defined as an ecological response unit (ERU). Subsystem characteristics of an ERU are considered homogenous, but between ER Us the characteristics may differ greatly. A set of ER Us may be arranged into any mosaic pattern, a quality that affords a unique response behavior to both the individual ERUs and the mosaic pattern. Discrete management events, such as controlled burning or livestock stocking, and continuous events, such as oil-shale mining, may be scheduled for a complex of ERUs. As the model operates "mechanistically," the results are tractable, and they provide a framework for interpretation and discussion among resource managers. A computer-based simulation model of the conceptual model, named An Ecosystem Simulation of Perturbations (AESOP), has been developed to provide resource managers with a methodology for analyzing the future consequences of multiple-use management scenarios. The computer model provides pseudoquantitative ecosystem responses as a consequence of various management strategies. AESOP allows a user to specify many types of scenarios involving both ecosystem characteristics and management practices, which may vary in location, timing, and magnitude. AESOP was programed in the general-purpose computer language PASCAL because of the superior data-typing and program­structuring capabilities of the language, which allow model flexibility not possible with most models reported in the ecological literature. AESOP closely imitates the conceptual model through data-structuring techniques and derived mathematical func­tions representing ecosystem relationships. The block structure of the computer program provides ease in understanding and evaluation by the user and change or interchange of simulation procedures. AESOP generates time-series data of the components and processes of the ERUs and indices of subsystem conditions. A separate analysis program summarizes the voluminous output into statistical tables and graphs. The model is currently being tested by evaluating ecosystem response to multiple-use resource management of the sagebrush­grass areas in northwestern Colorado. This region is unique in its richness of energy-producing resources, its abundance of wild herbivoJ"es, and its livestock and agricultural practices. Through analysis of the results from various management-policy scenario simulations, "hindsight" is available to the resource manager at the time of decision-making.