About GAIA GAIA Case Studies Global GIS Agenda 21 Country Data Model Database

olor Icon

Zimbabwe: Landuse in Dry Tropical Savannas

Savanna - Landscape and Regional Ecosystem Model

Model structure

The spatial structure

The model has a three scaled hierachical spatial structure.
  1. Landscape scale
  2. Subareas
  3. Facets
It is spatially explicit at the landscape scale. In other words, it is sensitive to spatial location at this scale.Grid cells cover landscapes or regional-scale ecosystems. Grid-cell is scaled to the spatial extent of the simulated ecosystem. It is spatially inexplicit at the subarea or patch scales. Within grid-cells the model is sensitive to the proportions of grid cell covered with subareas which correspond to fixed distributions of the physical factors like topography and soils. Within subareas the model simulates vegetation patches or "facets". These are defined by covers of herbaciouous plants, shrubs and trees. Therefore facet cover is a dynamic outcome of vegetation growth and mortality. Facet locations are not modeled, only frations of subareas that are covered by the facets.

Within subareas and facets, plant growth and soil and water budgets are modeled. The results are scaled up by multiplying by the fraction of the grid cell covered by each patch type (herbaciouous plants, shrubs and trees).

Modular structure

Savanna is made of several interacting sub-models, these are;
  1. Soil water sub-model
  2. Light sub-model
  3. Net primary production sub-model
  4. Plant population dynamics sub-models
  5. Plant fire responses
  6. Herbivory sub-model
  7. Ungulate population dynamics sub-model
  8. Ungulate distribution dynamics sub-model
  9. Predator sub-model
  10. Snow sub-model

The snow sub-model is not relevant for this particular case study.

Copyright 1995-2002 by:   ESS   Environmental Software and Services GmbH AUSTRIA