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- A combined structural and seasonal approach to assess wildfire susceptibility and hazard in summertimePublication . Bergonse, Rafaello; Oliveira, Sandra; Gonçalves, Ana; Nunes, Sílvia; da Câmara, Carlos; Zêzere, JoséWildfre susceptibility and hazard models based on drivers that change only on a multiyear timescale are considered of a structural nature. They ignore specifc short-term conditions in any year and period within the year, especially summer, when most wildfre damage occurs in southern Europe. We investigate whether the predictive capacity of structural wildfre susceptibility and hazard models can be improved by integrating a seasonal dimension, expressed by three variables with yearly to seasonal timescales: (1) a meteorological index rating fuel fammability at the onset of summer; (2) the scarcity of fuel associated with the burned areas of the previous year, and (3) the excessive abundance of fuel in especially fre-prone areas that have not been burned in the previous ten years. We describe a new methodology for combining the structural maps with the seasonal variables, producing year-specifc seasonal susceptibility and hazard maps. We then compare the structural and seasonal maps as to their capacity to predict burnt areas during the summer period in a set of eight independent years. The seasonal maps revealed a higher predictive capacity in 75% of the validation period, both for susceptibility and hazard, when only the highest class was considered. This percentage was reduced to 50% when the two highest classes were considered together. In some years, structural factors and other unconsidered variables probably exert a strong infuence over the spatial pattern of wildfre incidence. These fndings can complement existing structural data and improve the mapping tools used to defne wildfre prevention and mitigation actions.
- Recent trends in fire regimes and associated territorial features in a fire-prone Mediterranean regionPublication . Moreira, Francisco; Leal, Miguel; Bergonse, Rafaello; Canadas, Maria João; Novais, Ana; Oliveira, Sandra; Ribeiro, Paulo Flores; Zêzere, José; Santos, José LimaFire regimes in Mediterranean countries have been shifting in recent decades, including changes in wildfire size and frequency. We sought to describe changes in fire regimes across two periods (1975–1995 and 1996–2018) in a fire-prone region of central Portugal, explore the relationships between these regimes and territorial features, and check whether these associations persisted across periods. Two independent indicators of fire regimes were determined at parish level: fire incidence and burn concentration. Most parishes presented higher values of both indicators in the second period. Higher values of fire incidence were associated with lower population densities, lower proportions of farmland areas and higher proportions of natural vegetation. Higher levels of burn concentration were associated with smaller areas of farmland and natural vegetation. These associations differed across periods, reflecting contrasting climatic and socio-economic contexts. Keeping 40% of a parish territory covered by farmland was effective to buffer the increased wildfire risks associated with different management and climate contexts. The effectiveness of higher population densities in keeping fire incidence low decreased in the last decades. The results can improve the knowledge on the temporal evolution of fire regimes and their conditioning factors, providing contributions for spatial planning and forest/wildfire management policies.