Post-fire regeneration of Quercus sp. ecosystems in Alto Alentejo after 2003 wildfires

Abstract

Fire is an ecological constant in the Mediterranean ecosystems and plays an important role in ecosystems dynamics. In Portugal we can distinguish different fire regimes, and thus it’s important to study these different areas independently. However it’s difficult to establish the regeneration patterns because they are influenced by local biophysical characteristics, land use, fire behaviour and other disturbance factors. In other hand there was lack of information about post-fire in southern Portugal, particularly where fire is an infrequent phenomenon. Alto Alentejo was one of disaster zones after the great wildfires in 2003. In addition to high severity and extent of them, the fires have burned ecosystems that weren’t as susceptible to this disturbance factor. This paper aims to determine post-fire dynamics in three Quercus sp. ecosystems, dominated by Q. pyrenaica, Q. suber and Q. rotundifolia. Sampling has been carried out in Alto Alentejo (Southern Portugal). The floristical analysis, performed by applying phytosociological protocols, can comprise species composition and richness, species abundance and community diversity. We sampled phytosociologic inventories on plots that burned in 2003. These results were compared with inventories plots in well conserved areas that characterize the natural vegetation in the study area (reference area). All plants species were listed and given a double coefficient of abundance-dominance and sociability, and the plant taxa were characterized according its regeneration mode and life form. Phytosociologic relevés allows establishing the regressive or progressive successions of the plant communities. The results suggest that not all areas tends to recover next to the reference vegetation, particularly in Q. pyrenaica ecosystems. Shrublands of the associations Phillyreo angustifoliae-Arbutetum unedonis or Genisto falcatae-Adenocarpetum anisochili typical of these ecosystems were not found in the burnt area. In its place there is high invasion of Cytisus multiforus belonging to the association Cytisetum multifloro-eriocarpi. This is probably related to the cumulative effect of other disturbance factors such as overgrazing and fire use to promote pastures.