Natural Resource Ecology Laboratory
Colorado State University

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. CENTURY 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 sulfur through the model's compartments. The minimum configuration of elements is C and N for all the model compartments. The organic matter structure for C, N, P and S are identical, the inorganic components are computed for the specific inorganic compound. The timestep is or monthly and the model requires the following driving variables as input:

- Monthly average maximum and minimum air temperature
- Monthly precipitation
- Soil texture
- Plant nitrogen, phosphorus, and sulfur content
- Lignin content of plant material
- Atmospheric and soil nitrogen inputs
- Initial soil carbon, nitrogen (phosphorus and sulfur 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.

CENTURY was originally developed as a project of the U.S. National Science Foundation Ecosystem Studies Research Projects. Additional support for model enhancement has been provided by

Tallgrass Ecosystem Fire Project
Central Plains Experimental Range - LTER
NASA-EOS Project
Agricultural Research Service USDA

Link to the CENTURY webpage.


Metherall, A.K. (1992)
Simulation of soil organic matter dynamics and nutrient cycling in agroecosystems, Ph.D. Dissertation, Colo State University, Ft. Collins.
Metherall, A.K., L.A. Harding, C.V. Cole, W.J. Parton (1993)
CENTURY Soil Organic Matter Model Environment Technical Documentation, Agroecosystem Version 4.0, Great Plains System Research Unit, Technical Report No. 4. USDA-ARS, Ft. Collins.
Parton, W.J., D.W. Anderson, C.V. Cole, J.W.B. Stewart (1983)
Simulation of soil organic matter formation and mineralization in semiarid agroecosystems. In: Nutrient cycling in agricultural ecosystems, R.R. Lowrance, R.L. Todd, L.E. Asmussen and R.A. Leonard (eds.). The Univ. of Georgia, College of Agriculture Experiment Stations, Special Publ. No. 23. Athens, Georgia.
Parton, W.J., D.S. Schimel, C.V. Cole, D.S. Ojima (1987)
Analysis of factors controlling soil organic levels of grasslands in the Great Plains. Soil Science Society of America Journal. 51:1173-1179.
Parton, W.J., R. McKeown, V. Kirchner, D. Ojima (1992)
CENTURY Users' Manual, Natural Resource Ecology Laboratory, Colorado State University, Ft. Collins.
Hurricane effects on soil organic matter dynamics and forest production in the Luquillo Experimental Forest, Puerto Rico: Results of simulation modeling, Biotropica 23:364-372.

CENTURY Contacts:

Dr. William Parton
Natural Resource Ecology Laboratory
Colorado State University
Fort Collins, CO 80523

FAX: (303) 491-1965

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