Post-fire regeneration of Calicotome villosa (Poiret) Link. and vegetation analysis.

Calicotome villosa (Poiret) Link. is a leguminous deciduous shrub that is often associated with disturbance processes, such as fires. This species is characterised by a primary dormancy imposed by its water-impermeable seed coat. In the present study, the germination rate of untreated seeds was low (10%), whereas high germination rates were achieved with different scarification techniques. Germination tests demonstrated that seeds of C. villosa do not require exposure to high temperatures to germinate. Indeed the highest germination rate (97%) was obtained with mechanical scarification, by chipping the seed coat with a scalpel. Therefore, the effects of fire on dormancy breakage only arises from the scarification of the seed coat that is necessary for germination of the majority of seeds. This suggests that under natural conditions, few seeds germinate during non-fire years. This will contribute to maintenance of the population, whereas most of the seeds accumulate in the soil seed bank and can then germinate when a fire occurs and they are released from dormancy. This vegetation analysis leads to better definition of the environment and geographic context in which plant communities dominated by C. villosa develop. The phytosociological study focused primarily on the formations in the Gargano area, where relevés were carried out 4 years and 8 years after the widespread fires. The seeds for the study of seed germination were collected in this area. These unpublished relevés were compared with other relevés attributed to several Italian localities, such as the association Pistacio lentisci–Calicotometum villosae described for north-west Sardinia, and with relevés of the Sardinian association Phagnalo saxatili–Calicotometum villosae. This analysis led to recognition of some new associations: Spartio juncei–Calicotometum villosae; Teucrio fruticantis–Calicotometum villosae; Euphorbio dendroidis–Calicotometum villosae; Phagnalo saxatili–Calicotometum villosae typicum and asparagetosum stipularis. The relevés from Gargano were attributed to the new association Pino halepensis–Calicotometum villosae. The syntaxonomic attribution to the higher hierarchical levels refers the Tyrrhenian community to the new suballiance Pistacio lentisci-Calicotomenion villosae of the alliance Ericion arboreae (Pistacio lentisci–Rhamnetalia alaterni and Quercetea ilicis). The new Adriatic association Pino halepensis–Calicotometum villosae is related to the Balcanic alliance Cisto cretici–Ericion manipuliflorae, of the order Cisto cretici–Ericetalia manipuliflorae, and of the class Cisto cretici–Micromerietea julianae. The conclusions thus highlight the dissimilarities between the two vegetation classification systems. The suballiance Pistacio lentisci-Calicotomenion villosae is important in order to complete the western Mediterranean hierarchical system. Indeed, the communities belonging to the new suballiance are formed by both fast resprouting species (Pistacia lentiscus, Erica arborea, Myrtus communis and Arbutus unedo) and regenerative species by seed (Calicotome villosa, C. spinosa, Cistus sp. pl., Pinus halepensis etc.).