ALEPPO PINE (PINUS-HALEPENSIS) POSTFIRE REGENERATION - THE ROLE OF CANOPY AND SOIL SEED BANKS

Pinus halepensis (Aleppo pine), is the dominant tree of a large fracti on (26%) of the Greek coniferous forests; this species is an endemic p ine of the Mediterranean Rim and well adapted to fire. Its regeneratio n is accomplished exclusively through seeds, thus its soil and canopy seed banks are of paramount importance for postfire resilience. Cone o pening and seed dispersal were investigated in unburned forests of Att ica (Greece) and it was found that Pinus halepensis trees maintain a s ignificant percentage of the yearly cone crop (40-80%) closed, thus cr eating a persistent, canopy seed bank. Full viability of enclosed seed s was maintained for at least three years in canopy storage; moreover, preliminary results concerning the viability of seeds enclosed within the cones for four to more than 50 years showed a gradual reduction o f both final percentage and rate of germination. Nevertheless, cones o f up to 20 years of age contained a considerable fraction of germinabl e seeds. On the other hand, Aleppo pine forms only a short-lived (tran sient) soil seed bank; this bank was particularly abundant after a fir e, as a result of the fire-induced cone opening. The germinable seed p ortion, although quite important prior to the start of the rainy seaso n, was rapidly depleted, and at the end of the rainy season it was vir tually absent in both burned and unburned forests. It is therefore con cluded that postfire Aleppo pine seedling recruitment takes place almo st exclusively during the first year after the fire and depends upon t he germination of seeds in a transient soil bank which is produced by the postfire dispersal of pine seeds stored in the canopy seed bank.