Fire effects on the seed bank of three Mediterranean shrubs: implications for fire management

To evaluate fire effects on the soil seed bank of a Mediterranean heathland, soil and litter samples were collected under the three dominant shrub species (Erica australis L., Erica umbellata Loefl. ex L., and Pterospartum tridentatum (L.) Willk) before and after an experimental fire. Target plants were selected near to 12 points regularly spaced in a grid layout in a 50 × 50 m plot. Soil heating by the fire was estimated using thermocouples installed at 1.5 cm depth. The soil seed bank was dominated by E. australis and E. umbellata. Erica australis having statistically significantly higher germination densities under their conspecific shrubs. Pterospartum tridentatum was extremely underrepresented in the viable seed bank, despite being the dominant species in the vegetation. Fire did not produce significant differences in the overall germination, but post-fire germination density of E. australis was related to maximum temperatures recorded at 1.5 cm depth. Special focus was given to the seed bank of the obligate seeder E. umbellata and its possible implications in population regeneration after recurrent fires. There was, however, no evidence that current fire frequency would imply a risk of population decline, since E. umbellata seed bank is abundant despite the scarcity of adult shrubs.Paula Maia and Ana Vasques were funded through individual Ph.D. fellowships granted by FCT (Portuguese Foundation for Science and Technology) (SFRH/BD/42168/2007, SFRH/BD/47522/2008) and through individual research grants by the CASCADE project.Peer Reviewe