| Resum: |
Fire is one of the main disturbances in Mediterranenan ecosystems. In the recent decades, in Catalonia (NE Spain), the number of fires has decreased while burnt area has increased. This is related to changes in land use, climate and fire suppression policies which influenced horizontal and vertical fuel continuity. From all the factors influencing fire risk only fuel load is manageable by humans. For this reason it is important to understand the role of different land covers and forest structure in fire occurrence. This study aimed to understand the determinants of large fire occurrence at two different scales, 500m and 2000m around the ignition point (local and landscape scale, respectively). A binary logistic regression model was built using ignition points from the period 1989-2012 and considering 1000 control points. Forest structure variables obtained through interpolation techniques throughout Catalonia and land cover types were established as the independent variables at the two considered scales. A risk map for large fire occurrence in Catalonia was also built. Mediterranean pine forests and shrublands were the main variables influencing positively large fire occurrence. Specifically, Mediterranean pine forests with intermediate values of basal area and high understory increased the risk of large fires. Although large fires do not usually start in mixed forests, these forests were important at the scale at the landscape scale (2000m) probably because of their vertical continuity. Results showed that a multiscale management would be necessary which should focus on the landscape mosaic of different land cover types and less fire prone forest structures, particularly considering the uncertainty associated with global change and the large fires' risk increase throughout Catalonia. |
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