Spatial heterogeneity of fire spread and behaviour in a Sardinian wooded pasture

About the fifty per cent of the Sardinian island is covered by herbaceous vegetation mainly represented by grasses, open wooded pastures and not irrigated herbaceous crops. Except for the herbaceous crops, mainly concentrated in the agricultural plains of the western side, the other areas covered by herbaceous vegetation are embedded in a complex matrix together with shrubland vegetation and broadleaf forests; this fragmented landscape was produced by different anthropogenic disturbances, such as deforestation, grazing, forest fires, and other modifications of land use. Such landscape structure widely affects the fire spread and behaviour, as fire propagation is a combined effect of the involved environmental components: vegetation, weather, and terrain. In addition, the areas covered by herbaceous vegetation are characterised by a considerable frequency of ignitions, due to arson, causalities derived from the agricultural activities, and use of fire as agronomic practice to obtain the terrain free from shrubs and old grasses; the latter practice is typical of the traditional Sardinian agropastoralism. The aims of this study were (i) to use a fire spread simulator for estimating the probability of burning in a Mediterranean area predominantly covered by grasses and open wooded pastures, and (ii) to estimate the effects of the grazing pressure on the fire behaviour and severity, in relation to the different weather conditions observables in the experimental area. The study, conducted in the Central highland area of Sardinia, provided useful data in order to identify the areas with high probability of fire, high level of danger, and therefore, high potential fire risk. Fuel reduction strategies were tested by the simulator in order to plan the fire prevention and fire management practices.