The CENTURY model is a general model of plant-soil nutrient cycling which has been used to simulate carbon and nutrient dynamics for different types of ecosystems including grasslands, agricultural lands, forests and savannas.
The model is composed of a soil organic matter/decomposition submodel, a water budget model, a grassland/crop submodel, a forest production submodel, and management and events scheduling functions. It computes the flow of carbon, nitrogen, phosphorus, and sulphur through the model's compartments. The minimum configuration of elements is C and N for all the model compartments. The organic matter structure for carbon(C), nitrogen(N), phosphorus(P) and sulphur(S) are identical; the inorganic components are computed for the specific inorganic compound. The timestep is monthly and the model requires the following driving variables as input:
- Monthly average max and min air temperature
- Monthly precipitation
- Soil texture
- Plant nitrogen, phosphorus, and sulphur content
- Lignin content of plant material
- Atmospheric and soil nitrogen inputs
- Initial soil carbon, nitrogen (phosphorus and sulphur optional)
These variables are available for most natural and agricultural ecosystems. The soil organic matter submodel includes three soil organic matter pools (active, slow, and passive) with different potential decomposition rates, above and below ground litter pools and a surface microbial pool which is associated with decomposing surface litter. The simplified water budget model calculates monthly evaporation, transpiration, the water content of the soil layers, snow water content, and saturated flow of water between soil layers. As mentioned above, CENTURY contains two plant production submodels: a grassland/crop submodel and a forest production submodel. Both plant production models assume that the monthly maximum plant production is controlled by moisture and temperature, and that maximum plant production rates are decreased if there are insufficient nutrient supplies.
The grassland/crop production model simulates plant production for different herbaceous crops and plant communities (e.g. warm or cool season grasslands, wheat, and corn). The forest model simulates the growth of deciduous or evergreen forests in juvenile and mature phases. To simulate a savanna or shrubland, CENTURY uses both of these submodels with some additional code to simulate nutrient competition and shading effects. Disturbances such as fire, havest, grazing and cultivation can be simulated via the management and events scheduling functions.