A generic process-based SImulator for meditERRanean landscApes (SIERRA): design and validation exercises

Understanding the interrelationship that exists between landscape patterns and fire history requires a great range of case studies to reduce the effects of substrate and climate. The lack of such data has led to an increasing need for spatially explicit models dealing with vegetation dynamics. The challenge is to find a compromise between process complexity, realism and landscape applications. In this paper, we describe a simulation approach (SIERRA) focussed on the particular case of Mediterranean-type communities subjected to large recurrent fires. Firstly, disturbance response strategies used in vital attributes models are used to simulate the influence of fire on vegetation dynamics, focussing in particular on the integration of specific regeneration abilities of Mediterranean species. Next, the model takes a functional approach towards carbon and water budgets to drive competition and simulate the seasonal vegetation water status to estimate fire risk. Spatial processes of seed dispersal, surface water fluxes depending on topographic convergence, and fire spread are used to accurately simulate landscape heterogeneity. The model offers a spatial representation of the annual course of vertical structure of biomass and carbon fluxes coupled with the weekly soil water budget and evapotranspiration rates. Some simulation and validation exercises are presented to illustrate both the functional properties on a Quercus ilex stand, and the fire-prone community dynamics of a maquis shrubland. These initial results will form a strong basis for using the model to test hypotheses about fire-prone landscape patterns. (C) 2001 Elsevier Science B.V. All rights reserved.