Germination behaviour of 14 Mediterranean species in relation to fire factors: smoke and heat

Fire is an ecological factor that has been present in the ecosystems of the Mediterranean region for thousands of years. Our study was undertaken to acquire knowledge of the effect of fire on the germination of Mediterranean species. We used high temperatures (up to 60°C) and smoke to determine the effect of these factors on the germination of species from the Mediterranean region. The species selected are characteristic of the central Mediterranean basin and are representative of both woody and herbaceous species: Rhamnus alaternus L., Cistus albidus L., Cistus monspeliensis L., Fumana ericoides (Cav.) Gand., Rosmarinus officinalis L., Melica ciliata L., Avena sterilis L., Bituminaria bituminosa (L.) C.H. Stirt., Anthyllis vulneraria L., Coronilla glauca L., Argyrolobium zanonii (Turra) P.W. Balland, Emerus major Mill., Genista scorpius (L.) D.C. and Spartium junceum L. The seeds were collected in Mediterranean shrubland (8) and woodland (6) ecosystems, around Montpellier, France (24°45′N and 3°50′E). Ten treatments were tested: a control, three smoke treatments and six heat treatments. The average germination level (germination percentage) and the average T₅₀ rates (time taken to reach 50% of germination) were calculated. The smoke and heat act in a different way on each of the species. The smoke enhanced the germination of two species, whilst moderate heat increased germination in all of the species excepting R. officinalis, F. ericoides, A. sterilis, A. vulneraria, and G. scorpius. Germination was fastest in M. ciliata and S. junceum and slowest in A. sterilis, E. major and C. albidus. The cues did not significantly affect the rate of germination. Fire modified the germination response of 12 of the 14 species studied.