Soil seed banks in Mediterranean Aleppo pine forests: the effect of heat, cover and ash on seedling emergence

1 East Mediterranean Aleppo pine (Pinus halepensis) forests are subjected to periodic stand-replacing fires. We simulated two of the effects of fire on the germinable soil seed bank in four pine stands on Mt. Carmel, Israel, that differed in their postfire ages. Soil samples were heated to 100 degrees C, or covered by pine ash. Vermiculite was used to simulate litter cover. 2 Heat exposure increased overall seedling density, richness and taxon diversity in all stands, but density of annual taxa (e.g. grasses and legumes) were not clearly affected. 3 Ash cover dramatically decreased germination of all taxa and highest germination was achieved with heating and no cover. Vermiculite cover resulted in intermediate germination levels. 4 The combined effect of heat exposure and ash cover, simulating a post-fire situation under a canopy of pine, reduced the germination level of all taxa in the soil seed bank. However, it also creates conditions that facilitate the establishment of pine seedlings from the canopy stored seed bank.