nutria readme

(I) AUTHORSHIP
DATE: March 5 1998
TITLE: Nutria-Marsh Biomass-Marsh Area Loss ModelAUTHORS: Jacoby Carter, A. Lee Foote, and Lori A. JohnsonAFFILIATION: U.S. Geological Survey-National Wetlands Research CenterADDRESS: 700 Cajundome Blvd. Lafayette, LA 70506PHONE: 337-266-8620FAX: 337-266-8586E-MAIL: jacoby_carter@usgs.gov

(II) NOTES

(A) Running the Model

This version of the model has been translated from STELLA Research Version 4.0 to 5.0. There are no functions included in this version that will prevent it from being run using STELLA Standard Version 5.0. This model will run on either Macintosh or Windows platforms. To download the model click Nutria.stm.hqx.

If you either don't have STELLA or have an earlier version of STELLA you can download a runtime version of STELLA to run the model from the High Performance Systems Inc. web site: STELLA

(B) Abstract

We created a model to study nutria the process in which nutria (Myocastor coypus) feeding activities lead to erosion and loss of marsh area. This model ties together data on nutria population dynamics and feeding behavior from the literature with data from field studies on the phenology of Scirpus americanus and Spartina patens conducted in the Barataria basin, Louisiana, USA, in 1992. The complete model consists of three linked models: a model of nutria population dynamics (nutria model), a model of the annual marsh biomass cycle of Scirpus americanus and Spartina patens (biomass model), and a plant-biomass density-dependent marsh area model (area model). When all three models are linked together they form the "nutria-biomass-area model."

Analysis of the models indicated the following: (1) Highest population densities and survivorship rates reported in the literature are incompatible. Either survivorship is higher than reported, or population densities are lower than reported. (2) The nutria model is sensitive to adult and juvenile survivorship, and to a lesser extent young born per female. It is not particularly sensitive to gestation periods, impregnation rates, or time to maturity. (3) The marsh area model is not sensitive to the marsh loss equation or to the density at which loss of marsh area begins, but is sensitive to the amount of biomass destroyed per nutria. (4) Nutria numbers do not significantly decline in the nutria-biomass-area model until the total marsh area approaches zero because marsh loss occurs only during winter when marsh biomass is at its annual low. (from: Carter, Foote, and Johnson 1998, in prep)

You are free to use the model for educational and research purposes but not for commercial purposes. You are free to distribute the model as long as you (1) include this text file with the model, (2) document any modifications you have made in the model, and (3) full and proper attribution of our authorship is maintained. If you wish to use the model for commercial purposes you need to contact the first author.

(III) DISCLAIMERS

(A) Use of STELLA in this model does not constitute an endorsement of this product.

(B) This model is distributed "as is" and only for educational and research purposes. We make no claims for its suitability for any particular purpose.

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