1. General Model Information

Name: Simulation of a Semi-Arid Grazing System

Acronym: SIMSAGS

Main medium: terrestrial
Main subject: wildlife and livestock, other, agriculture, population dynamics
Organization level: Landscape, Ecosystem
Type of model: mechanisms of animal-plant interactions, other, rule based, not specified (3D)
Main application: decision support/expert system, simulation/optimisation tool, research
Keywords: semi-arid, grazing, ungulate, ruminant, wildlife, livestock, Africa, Mongolia, resource-poor farming, optimal solutions


Dr. J.F. Derry
Institute of Evolutionary Biology, School of Biological Sciences,
University of Edinburgh, Ashworth Labs,
Kings Buildings, West Mains Rd.,
Edinburgh, EH9 3JT, Scotland, UK.
Phone: +44 (0)131 651 3631
email: j.derry@ed.ac.uk
Homepage: http://sags.bio.ed.ac.uk/


A.W.Illius, J.F.Derry, I.J.Gordon


The model runs on a daily iteration interval and uses daily rainfall data to calculate vegetation growth and its allocation to plant parts, the selection and intake of these by animals, the animals' consequent energy and protein balances, body growth, reproduction and mortality. It therefore simulates animal population dynamics mechanistically, i.e. by coupling them to vegetation biomass dynamics. The model can be run without animal sales, in which case the ecological carrying capacity of the system is expressed (as the size of the animal population maintained by intake-dependent birth and mortality, without offtake), or with a range of animal sales policies. A detailed description of the animal component of the model has been presented by Illius and Gordon (1998), with an outline of the plant component. They also presented results showing that the model gives reasonable predictions of the relationship between the long-term mean ecological carrying capacity and mean annual rainfall (Fritz and Duncan, 1994). The model structure is addressed by Derry (1998), with a more detailed description in Derry (2004) and in preparation. Spatial aspects of the model include topography, soil nutrient distribution, surface water dynamics, plant distribution, drinking water location and animal spatial foraging behaviour.

II. Technical Information

II.1 Executables:

Operating System(s): Windows 98, 2000, XP

II.2 Source-code:

Programming Language(s): Borland C++

II.3 Manuals:

published literature

II.4 Data:

III. Mathematical Information

III.1 Mathematics

see website

III.2 Quantities

III.2.1 Input

III.2.2 Output

IV. References

see website

V. Further information in the World-Wide-Web

VI. Additional remarks

successfully applied to contexts in South Africa, Zimbabwe, Botswana, Namibia, Kenya and Mongolia. Part of LPP Project R6984 "Environmental variability and productivity of semi-arid grazing systems" Help system in development Further model applications under review
Last review of this document by: : Mon Nov 1 16:46:43 2004
Status of the document: Contributed by J.F.Derry
last modified by Joachim Benz Mon Feb 13 08:45:49 CET 2006

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