The soil seed bank in range ecosystems of Psilorites mountain in Crete

The soil seed bank is considered as a genetic reserve of the populations, which helps them to recover after a disturbance (e.g. fire, erosion) or after the cessation of a pressure such a grazing. In this research, the soil seed bank of 30 sites with different fire and grazing histories was measured. From each of the 30 study sites, 20 soil cores of 5 cm deep and 5.7 cm wide (about 127 cm3) were taken. Of those 10 cores were taken under phrygana and 10 away from phrygana. In the laboratory, they were air dried for 2-4 weeks, sieved with a 4mm wire mesh; subsequently they were put in plastic containers in the greenhouse, where they were irrigated with a mist system every 2-4 days. The seedlings were counted and removed when they were identifiable or transplanted to other containers in order to be identified later. The number of seeds recorded varied from 509 seeds/m2 in a grazed forested rangeland to 47.339 seeds/m2 in a grazed grassland site. The number of seeds was significantly higher away from phryganic species than under their canopy. In burned and grazed phryganic sites, the number of seeds in the soil was significantly lower than in unburned and grazed phryganic sites for all plant categories except phrygana. In grasslands, the number of seeds was higher in grazed than in ungrazed sites. It is concluded that the soil seed bank was richer in overgrazed sites indicating a resilience of the studied ecosystems to the action of animals, while the combination of overgrazing and wildfires significantly reduced the soil seed bank.