SIMULATING THE DYNAMICS OF A VEGETATION MOSAIC - A SPATIALIZED FUNCTIONAL-MODEL

Space needs to be taken into account in vegetation dynamics models whi ch deal with heterogeneous systems. Most landscapes, at a given scale, are mosaics of relatively homogeneous patches. Some patches act as so urces of energy, matter or individuals, others as sinks. The dynamics of each patch depends partly on the flows which relate it to its neigh bours. Simulating the functioning of these systems lead to combine, in the same model, within-patch dynamics, ecotone dynamics, and the inte ractions between patches and flows. The model TLALOC uses these princi ples to simulate the dynamics of a two-patch system from an arid zone which clearly depend on surface water flows. In each m(2) of a transec t perpendicular to an ecotone, both functional (water and carbon budge ts) and dynamics processes (recruitment and survival) were simulated. Despite the simplifications, it satisfactorily modelled the functionin g of the studied vegetation. It highlighted the importance of consider ing various temporal and spatial scales and the possible consequences of including the studied transect in an even larger landscape.