Quoted from: https://daac.ornl.gov/cgi-bin/dsviewer.pl?ds_id=808 

The Integrated Biosphere Simulator (or IBIS) is designed to be a comprehensive model of the terrestrial biosphere. The model represents a wide range of processes, including land surface physics, canopy physiology, plant phenology, vegetation dynamics and competition, and carbon and nutrient cycling. The model generates global simulations of the surface water balance (e.g., runoff), the terrestrial carbon balance (e.g., net primary production, net ecosystem exchange, soil carbon, aboveground and belowground litter, and soil CO2 fluxes), and vegetation structure (e.g., biomass, leaf area index, and vegetation composition). IBIS was developed by Center for Sustainability and the Global Environment (SAGE) researchers as a first step toward gaining an improved understanding of global biospheric processes and studying their potential response to human activity [Foley et al. 1996]. IBIS was constructed to explicitly link land surface and hydrological processes, terrestrial biogeochemical cycles, and vegetation dynamics within a single, physically consistent framework. Furthermore, IBIS was one of a new generation of global biosphere models, termed Dynamic Global Vegetation Models (or DGVMs), that consider transient changes in vegetation composition and structure in response to environmental change. Previous global ecosystem models have typically focused on the equilibrium state of vegetation and could not allow vegetation patterns to change over time. Version 2.5 of IBIS includes several major improvements and additions [Kucharik et al. 2000]. SAGE continues to test the performance of the model, assembling a wide range of continental- and global-scale data, including measurements of river discharge, net primary production, vegetation structure, root biomass, soil carbon, litter carbon, and soil CO2 flux. Using these field data and model results for the contemporary biosphere (1965-1994), their evaluation shows that simulated patterns of runoff, NPP, biomass, leaf area index, soil carbon, and total soil CO2 flux agreed reasonably well with measurements that have been compiled from numerous ecosystems. These results also compare favorably to other global model results [Kucharik et al. 2000].

Below are quoted from: http://nelson.wisc.edu/sage/data-and-models/model-code.php 

The Earth's terrestrial (land-based) ecosystems are critically important to the welfare of humankind. Food, fiber, fresh water, medicines, and forest products are all derived from our terrestrial ecosystems. In addition, terrestrial ecosystems play a central role in regulating the biogeochemical and climate systems of this planet.

To better understand ecological processes, and to evaluate their response to human activity, our research team developed IBIS (the Integrated BIosphere Simulator) - a comprehensive computer model of the Earth's terrestrial ecosystems.

IBIS simulates a wide variety of ecosystem processes, including:

• energy, water, and carbon dioxide exchange between plants, the atmosphere, and the soil
• physiological processes of plants and soil organisms, including photosynthesis and respiration
• seasonal changes of vegetation, including spring budburst, fall senescence, and winter dormancy
• plant growth and plant competition
• nutrient cycling and soil processes

IBIS is one of the few computer models to incorporate this range of processes in a single framework.

We have used the model to study how ecosystems respond to changes in land use and climate. The IBIS model was tested against detailed field measurements collected from ecosystems around the world.

IBIS is described in

Kucharik, C.J., J.A. Foley, C. Delire, V.A. Fisher, M.T. Coe, J. Lenters, C. Young-Molling, N. Ramankutty, J.M. Norman, and S.T. Gower (2000). Testing the performance of a dynamic global ecosystem model: Water balance, carbon balance and vegetation structure. Global Biogeochemical Cycles 14(3), 795-825.

and

Foley, J.A., I.C. Prentice, N. Ramankutty, S. Levis, D. Pollard, S. Sitch, and A. Haxeltine (1996). An integrated biosphere model of land surface processes, terrestrial carbon balance, and vegetation dynamics. Global Biogeochemical Cycles 10(4), 603-628.

Downloads
IBIS 2.6b4 Code
Params Files
Input Files

PLEASE NOTE: This code is available only to check the model as it was used in our research papers. Due to funding constraints, we cannot offer technical help on an individual basis, but consider joining the IBIS yahoo group for current user discussion and about running IBIS.