Five Decades of Ecosystem Model Development and Current Efforts to Address Contemporary Ecological Issues.

One of the first ecosystem models developed in the 1970’s was the ELM grassland model. Extensive field observations from the International Biological Program were used to represent almost all processes (species level plant growth, soil C and N cycling, insect and mammal predation, etc.). Unfortunately, the ELM model was too complex to use for practical management questions. However, the soil temperature, water and nutrient cycling sub models were used in later, simpler, ecosystem models including CENTURY.  During the 1980’s CENTURY was used for site level simulations while regional application was limited due to lack of climate, soils, and plant production data. Funding for model development in the 1990’s led to model improvement and allowed for coarse scale regional simulations and the first large scale ecosystem model comparisons using standard weather, soils and land use data. As interest in climate change and greenhouse gas emissions grew in the late1990’s and 2000’s, the DayCent model was developed to simulate fluxes of the full suite of biogenic GHGs (CO2, N2O, CH4, NOx). DayCent was, and continues, to be applied to estimate soil GHG fluxes for the US National GHG Inventory, to compare the impacts of conventional vs. improved land management strategies for decision support tools (e.g. COMET-FARM) and perform life cycle assessments. Availability of large, standardized data sets (e.g., GRACEnet) has facilitated model evaluation and improvement. Current research needs include software development to generate model input files and funding for organized model comparisons is needed.