Modular ecosystem modeling

The modular ecosystem modeling approach was used to create a flexible landscape model structure that is easy to modify and extend for particular case studies and applications. The Library of Hydro Ecological Modules (LHEM; http://iee.umces.edu/LHEM) includes modules that describe hydrologic processes, nutrient cycling, vegetation growth, decomposition, etc., both locally and spatially. LHEM is implemented within the framework of the Spatial Modeling Environment (SME; http://iee.umces.edu/SME3) that integrates modules and places local simulation models into a spatial context. The LHEM was used to build the Patuxent Landscape Model (PLM) as well as models of several subwatersheds of the Patuxent. Local ecosystem dynamics are replicated across a grid of cells that compose the rasterized landscape. Different habitats and land use types translate into different parameter sets that drive the modules chosen. Spatial hydrologic modules define horizontal fluxes of material and information and link the cells together. Results show good agreement with data for several components of the model at several scales. The modular structure was essential to refocus the model on several problems associated with different management decisions that were to be made.