Fire intensity and serotiny: response of germination and enzymatic activity in seeds of Pinus halepensis Mill. from southern Italy

The Mediterranean Basin is a fire-prone area. Pinus halepensis Mill. is a naturally growing conifer which is frequently used for reforestation and restoration as it displays some degree of adaption to fire. One of the traits conferring tolerance to fire is the frequent presence of serotinous cones that are thought to protect seeds from fire damage. We checked for the physiological responses of seeds to different intensities of fire and related them to the degree of serotiny of the cones. Germination percentage, mean germination rate and enzymatic activity (alpha-amylase and protease) were recorded for seeds burned either free or enclosed in cones. We included as experimental factors the following: fire intensity, serotiny and time during which seeds were stored in cones after harvesting and germination stage. Burned seeds (released and enclosed) developed in serotinous cones exhibited higher heat insulation. In released seeds, germination was decreasing according to increasing fire intensity, although we found differences depending on site, serotiny and time stored after harvesting. The enzymatic activity was also found to be related to serotiny and fire intensity. Serotiny is an adaptive trait increasing the tolerance to fire which should be promoted in natural and restored populations.