CARAIB (CARbon Assimilation In the Biosphere) is a state-of-the-art dynamic vegetation module. It includes various modules describing (1) the soil water budget, (2) photosynthesis and stomatal regulation, (3) autotrophic respiration and allocation of photosynthetic products to a metabolic (leaves) and a structural (roots, stem, branches) reservoir, (4) heterotrophic respiration, litter and soil organic carbon budgets, (5) establishment competition and mortality of plant types, (6) vegetation fires, (7) ecosystem management and land use dynamics.
The model can be run with plant functional types (PFTs) or species. In ISIMIP, PFTs were used.
There are 6 land use categories: natural ecosystems, croplands, pastures, cities, water bodies and unfertile soils (or rocks). Only the first three categories can contain vegetation. In the natural ecosystem category, two vegetation storeys are defined. The understorey contains herbs and shrubs, while the overstorey include trees. Only one storey is defined in croplands and pastures. Forests are included in the natural ecosystem land use category, even if they are planted.
Indeed, a module allows the user to define management of natural ecosystems (planting, thinning, clearcut).
The global classification of plant types used in ISIMIP contains 44 PFTs, of which 26 in natural ecosystems (3 herbs, 8 shrubs and 15 trees), 16 in croplands, 2 in pastures.
