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O conhecimento do comportamento do fogo é essencial quando se quer organizar uma estratégia de controle de incêndios. A grande diversidade de elementos dos quais o fogo depende, torna a sua predição muito difícil, conduzindo muitas vezes a situações em que qualquer tentativa de extinção é fracassada. O sistema BEHAVE consiste numa série interactiva de programas de computador em linguagem Fortran VII, que permite prever o comportamento do fogo mediante a análise dos combustíveis da área em estudo. Este sistema é por sua vez dividido em dois outros sub-sistemas; o FUEL, que é responsável pela modelação dos combustíveis e o BURN que faz a previsão do comportamento do fogo. Na execução deste trabalho criaram- se novos modelos com base no sistema referido, sendo aplicáveis a quatro tipos de ecossistemas presentes no Parque Natural da Serra de S. Mamede.

The S. Mamede Natural Park includes a mountain area, distributed along S. Salvador de Aramenha (Marvão municipality) and S. Julião (Portalegre municipality) regions. Contrasting with the population evolution in Portugal for the last 20 years (+4%) the population decreased 27% in Marvão and 6% in Portalegre. The number of people in farming business in both municipalities decreased around 34% (1989-1999). In S. Salvador the evolution was similar; however in S. Julião the decrease was just 13%. Did that land abandonment induce significant landscape changes? The land use was mapped in two different moments (1967 and 2001) and compared using ArcView GIS software. Official statistical data was used to complement the spatial analysis (population and agricultural census). In 1967, the intensive forest in S. Julião represented 20% from total area (4223 ha) as comparing with 9% from S. Salvador total area (4972 ha). The olive grove area was 18% in S. Julião and 29% in S. Salvador. Open fields represented 21% and 25% in S. Julião and S. Salvador respectively. The increase in intensive forest use (1967-2001) was more than 120% for both regions; however, these changes had different origins. In S. Salvador the increase was due to areas being occupied for several uses, namely shrublands, olive groves and orchards; in S. Julião the change resulted from the open field areas being replaced. The open fields area decreased 70%, representing only 6% of the total area of S. Julião at the present. Perhaps reflecting these changes, at S. Julião region the stock number did not change significantly as comparing with S. Salvador, where the number of heads increased (1972-1999) with emphasis on sheep (119 to 4377 ewes). Most likely, farming in open fields changed from cereals to pastures production supporting this livestock increase. New land uses emerging in S. Salvador (golf courses, water bodies and fabric) might be qualitatively important and reflect the establishment of other economic activities, absorbing people from farming business.