Strategy for a fire module in dynamic global vegetation models
Résumé
Disturbance plays a major role in shaping and main-
taining many of the Earth’s terrestrial ecosystems. In
fact, many ecosystems depend on fire for their very
existence. Global Change is expected to result in
changed distribution of current ecosystems, changed
composition of those ecosystems, and in creation of
new ecosystems. The International Geosphere
Biosphere Program (IGBP), through the Core Projects
Biospheric Aspects of the Hydrological Cycle,
International Global Atmospheric Chemistry, Global
Change and Terrestrial Ecosystems and International
Global Atmospheric Chemistry, Biomass Burning
Working Group, recognized that disturbances need to
be included in the modeling efforts of each project.
Disturbance from fire. land use and other factors may be as important as climate change in shaping future landscapes (Weber and Flannigan 1998). Three main themes were recognized: impact of disturbance on carbon pools, vegetation change, and feedbacks to the atmosphere. In June 1998, a workshop was held in Potsdam, Germany to develop a strategy to introduce disturbance into dynamic global vegetation models. This strategy was based on the fact that vegetation burning influences atmospheric chemistry, that feedbacks of energy, water and trace gases to the atmosphere are influenced by vegetation, and that changes in the composition of ecosystems have direct impact on the carbon pool, on biodiversity, and on health and productivity of the land. Disturbance includes fire, insect, disease, drought and flooding, land conversion, land use, air pollution, and introduction of exotic species. While it will be necessary to ultimately include all disturbances, the Potsdam workshop limited itself to fire. This strategy is based on the fact that there are no process driven models for all disturbances, and that fire has a number of reliable models with which to begin the process of introducing disturbance into dynamic global vegetation models. While this workshop limited itself to fire, a great deal of consideration was given to the fact that the model shell must be able to include other disturbances in the future. As a result, the strategy was to focus on a hazard function which would lead to effects of disturbance. The hazard function is basically a probability statement of risk of effects. This approach seems equally valid for all forms of disturbance.
