Non-spatial calibrations of a general unit model for ecosystem simulations

General Unit Models simulate system interactions aggregated within one spatial unit of resolution. For unit models to be applicable to spatial computer simulations, they must be formulated generally enough to simulate all habitat elements within the landscape. We present the development and testing of a unit model for the Patuxent River landscape in the state of Maryland, USA. The Patuxent Landscape Model (PLM) is designed to simulate the interactions among physical and biological dynamics in the context of regional socioeconomic behavior. The PLM is a tool for evaluating landscape change within the Patuxent watershed through simulation of ecological systems. A companion economic model estimates land development patterns and effects on human decisions from site characteristics, ecosystem properties, and regulatory paradigms. Landscape elements that are linked within the PLM are forest, agriculture and open water systems, and three levels of urban development. Urban developments are low and medium density residential areas (14.07% of the total watershed), and commercial, industrial and institutional area (5.7%). Forests are mixed populations of deciduous and evergreen species (45.11%). Agricultural areas (28.02%) are simulated through rotating crops of corn, winter wheat and soybeans within a cycle of two years. Open water (6.84%) represents the ecosystems within the rivers and streams where phytoplankton are the primary producers. In this paper we illustrate, how we gathered and formalized working models used within the Patuxent watershed for forests, agriculture urban settings and wetlands. Further, we show how we tested and merged the variety of models employed by scientific disciplines and created a general unit model to be used in the Patuxent Landscape Model (Pat – GEM). The Patuxent Landscape Model is built under the Spatial Modeling Environment. © 2001 Elsevier Science B.V. All rights reserved.

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