16 Aspects of Demography in Post-Fire Mediterranean Plant Communities of Greece

Fire is a major ecological factor in many biomes of the world (Rundel 1981). In the Mediterranean ecosystems fire acts as an integral part of their evolutionary history, having shaped their adaptive traits (Naveh 1975). It is beyond any doubt that the specific characteristics of fire regimes have a profound effect on these ecosystems (Mooney and Conrad 1977), the most important of which is related to community and population structure. These are critical issues for any conservation attempt. In this perspective, the biological features that are mostly influenced by fire are reproductive and demographic characteristics which assure a rapid reestablishment by resprouting andlor seed germination (Keeley and Zedler 1978; Arianoutsou and Margaris 1981a). The specific regeneration behaviour of the plants is closely related to their physiological traits and is strongly influenced by fire regime (fire season, intensity, interval). Resprouting occurs from dormant buds or lignotubers effectively protected by the soil. It starts almost immediately after fire in the evergreen sclerophyllous species, while it takes several months, until the onset of the rainy season for the seasonal dimorphic (phryganic) species. This difference has been attributed to the different depths of their root systems. The resprouting ability of the plants is determined by their developmental phase. Many shrubby taxa are successful resprouters, either obligate or facultative. In several Mediterranean ecosystems, fire has been shown to trigger a flush of germination (Purdie 1977; Trabaud 1980; Arianoutsou and Margaris 1981b). Post-fire seed germination is an adaptation of the species which form permanent soil seed banks of hard-coated seeds (Cistaceae, Leguminosae) and of those with a canopy seed bank (Proteaceae, Pinaceae). Seed germination has been attributed to several factors such as mechanical rupture of the hard seed coat induced by the increased temperatures developing during fire (Arianoutsou and Margaris 1981b; review