RHESSys: Regional Hydro-Ecologic Simulation System--An Object-Oriented Approach to Spatially Distributed Modeling of Carbon, Water, and Nutrient Cycling.

Process-based models that can represent multiple and interacting processes provide a framework for combining field-based measurements with evolving science-based models of specific hydroecological processes. Use of these models, however, requires that the representation of processes and key assumptions involved be understood by the user community. This paper provides a full description of process implementation in the most recent version of the Regional Hydro-Ecological Simulation System (RHESSys), a model that has been applied in a wide variety of research settings. An overview of the underlying (Geographic Information System) GIS-based model framework is given followed by a description of the mathematical models used to represent various biogeochemical cycling and hydrologic processes including vertical and lateral hydrologic fluxes, microclimate variability, canopy radiation transfer, vegetation and soil microbial carbon and nitrogen cycling. An example application of RHESSys for a small forested watershed as part of the Baltimore Long-Term Ecological Research site is included to illustrate use of the model in exploring spatial-temporal dynamics and the coupling between hydrology and biogeochemical cycling. [ABSTRACT FROM AUTHOR]