Sblogo499.gif (4312 bytes) Stable Isotope Model
> Papers & reports
> SIM model
> Newsletters
> Gallery

Please note: This research Programme is no longer active





Downloading SIM
The Modelling Team

A key output of the NERC Soil Biodiversity Programme is SIM (Stable Isotope Modelling), a Windows-based program that provides the user with the facility to design food webs and simulate 13C pulse labelling experiments over a specific duration. SIM has been developed through a contract let to a team of from the Universities of Cambridge and York. The model and the software was produced based on data and observations made during the Soil Biodiversity Programme. Programme researchers were consulted on the model and software at a number of workshops hosted by the modelling team. 

The basic food web model is based on that described in Hunt et al. (1987) and Berg et al. (2001). To this basic framework has been added the facility to simulate 13C pulse experiments through the food web, enabling the user to validate the modelís outputs against newly available stable isotope data (Fitter et al. 2005). The underlying food web model envisages the soil ecosystem as a network of connected boxes, each box corresponding to a species or functional group and the connections representing directed trophic linkages between them. The central assumption is that the biomasses in all functional groups remain constant over time (the default unit of time is one year in the software) so that, for each functional group, one can assert biomass gained = biomass lost. The implementation of this basic principle across the web uniquely defines all the carbon flows. In practice, the situation is more complicated, involving mortality, variable prey preferences, and production and assimilation efficiencies.

SIM can be downloaded from this page - see below. An user guide describing how to use the model is also available.

For further information about SIM please contact:

Jon Pitchford
Dept of Biology
The University of York
PO Box 373

Tel: +44 (0)1904 328559





Downloading SIM
Note: SIM is designed to run on IBM compatible PCs running Microsoft Windows 9x, 2000, Me, NT and XP.

SIM user guide 701 Kb Microsoft Word Document Provides information on how to use the software, as well as details of the model itself. You are advised to  read this file before using the software.
SIM installation file - executable 4.7 Mb exe file (Application) Running this application will automatically install SIM on your computer. Download it to a destination folder of your choosing on your PC. When you run the programme you will be taken through a simple series of steps to install SIM.
SIM installation file - Zip file 4.7 Mb Zip file (compressed file) This is a Zipped version of the installation executable programme and is provided as an alternative file should you experience problems downloading the exe file. You will need a copy of WinZip in order to unpack this file.

If you experience problems downloading, installing or running the software, please contact Jon Pitchford (details above) for assistance.


The modelling team

University of York University of Cambridge
Alistair Fitter Chris Gilligan
Kirsty Hollingworth Adam Kleczkowski
Jon Pitchford


Berg M, DeRuiter P, Didden W, Jansen M, Schouten T, and Verhoef H (2001) Community food web, decomposition and nitrogen mineralization in a stratified Scots pine forest soil. OIKOS 94, 130-142.

Fitter AH, Gilligan CA, Hollingworth K, Kleczkowski A, Twyman RM, Pitchford JW and the members of the NERC Soil Biodiversity Programme (2005) Biodiversity and ecosystem function in soil Func. Ecol. (in press).

Hunt HW, Coleman DC, Ingham ER, Ingham RE, Elliott ET, Moore JC, Rose SL, Reid CPP and Morley CR (1987) The detrital food web in a shortgrass prairie. Biol. Fert. Soils 3, 57-68.