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The multiple element limitation (MBL MEL) model is a process based ecosystem model describing the plot scale dynamics of plants and soils. It is quantitative synthesis of the Mooney-Bloom-Chapin Resource-Optimization hypothesis of plant nutrition (Mooney 1972, Bloom et al. 1985, Chapin et al 1987; also called the "functional equilibrium hypothesis," Farrar and Jones 2000) within a whole-ecosystem context (Rastetter et al. 1997a). The resource-optimization hypothesis predicts how plants should allocate their internal assets (biomass, proteins, carbohydrate...) to acquire resources from the environment (CO2, NH4, NO3, water, light...). In an environment where resource concentrations do not change, the optimum allocation of internal assets is one where all resources in the environment equally limit production (Chapin et al. 1987); otherwise too many assets would be expended toward acquiring a non-limiting resource and a reallocation of those assets toward limiting resources would therefore increase production. Changes in resource availability and in metabolic requirements through time complicate this picture, but the overall concept still applies: plants should constantly adjust the distribution of their internal assets to approach a more balanced rate of resource uptake from the environment (e.g., shifts in root-shoot ratios, allocation of N). Selective pressure should strongly favor species that maintain a near optimum allocation pattern. We use an analogous approach to simulate soil microbial processes. However, because changes in microbial community composition and acclimation of microorganisms to changes in the environment are much faster than acclimation in vegetation, we treat the reallocation of effort for soil processes as instantaneous.

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Source Code

The full MBL-MEL source code, plus a windows executable and sample input files, is available for noncommercial use. See the download page for available versions.

Publications

Herbert, D. A., E. B. Rastetter, G. R. Shaver, G. I. Ågren. 1999. Effects of plant growth characteristics on biogeochemistry and community composition in a changing climate. Ecosystems 2:367-382. doi:

Herbert, D. A., M. Williams, and E. B. Rastetter. 2003. A modeled analysis of N and P limitation on carbon accumulation in an Amazonian forest site after alternate land-use abandonment. Biogeochemistry 65: 121-150. doi:

Herbert, D. A., E. B. Rastetter, L. Gough and G. R. Shaver. 2004. Species diversity across nutrient gradients: An analysis of resource competition in model ecosystems. Ecosystems 7: 296-310. doi:

Rastetter, E. B., G. I. Ågren and G. R. Shaver. 1997. Responses of N-limited ecosystems to increased CO₂: A balanced-nutrition, coupled-element-cycles model. Ecological Applications 7:444-460. doi:

Rastetter, E. B., and G. R. Shaver. 1992. A model of multiple element limitation for acclimating vegetation. Ecology 73:1157-1174. doi:10.2307/1940666.��

Rastetter, E. B., and G. R. Shaver. 1995. Functional redundancy and process aggregation: Linking ecosystems to species. In: C. G. Jones and J. H. Lawton (eds.) Linking Species and Ecosystems. Chapman and Hall, New York, pp. 215-223.

Rastetter, E. B., S. S. Perakis, G. R. Shaver, and G. I. Ågren. 2005. Carbon Sequestration in Terrestrial Ecosystems Under Elevated CO₂��and Temperature: Role of Dissolved Organic N Loss. Ecological Applications 15:71-86. doi:

Rastetter, E.B., P.M. Vitousek, C. Field, G.R. Shaver, D. Herbert, G.I. Ågren. 2001. Resource Optimization and Symbiotic N Fixation. Ecosystems 4:369-388. doi:

Rastetter, E.B., R.D. Yanai, R.Q. Thomas, M.A. Vadeboncoeur, T.J. Fahey, M.C. Fisk, B.L. Kwiatkowski, and S.P. Hamburg. 2013. Recovery from disturbance requires resynchronization of ecosystem nutrient cycles. Ecological Applications. 23:621-642. doi:

A zip file containing the model description, model executable, parameter and driver files for all figures is available��here.

Rastetter, E.B., R.D. Yanai, T.J. Fahey, M.C. Fisk, B.L. Kwiatkowski, G.R. Shaver, and M.C. Mack. In preparation. A biogeochemical theory of primary and secondary succession.

This material is based upon work supported by the National Science Foundation under grants #OPP-9318529, OPP-9732281, DEB-9509613, DEB 0716067 (OPUS), DEB-0108960, ARC-0806329, EF-1065587, ARC-0856853, and DEB-0949420 and the Environmental Protection Agency under grants RFQ-RT-00-00107 and QT-RT-00-001667. Any opinions, findings, conclusions, or recommendations expressed in the material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation or the Environmental Protection Agency.