Canopy seed banks in Mediterranean pines of southeastern Spain:: a comparison between Pinus halepensis Mill., P. pinaster Ait., P. nigra Arn. and P. pinea L.

1 Canopy seed banks were analysed in post-fire stands of Pinus halepensis, P. pinaster, P. nigra, and P. pinea. We determined age when flowering begins, age of first cone bearing, presence of serotinous cones and cone-opening temperatures. 2 By 15 years after the fire, P. halepensis had developed a large canopy seed bank (3-100 x 10(4) seeds ha(-1)). Fruiting started at 5 years of age. More than 86% of the cones were serotinous and had opening temperatures from 49.3 to 51.3 degreesC. Cones from adult trees opened at lower temperatures than those from young trees. 3 A 16-year-old P. pinaster stand had a smaller seed bank (12 000 viable seeds ha(-1)) and a lower percentage of serotinous cones (66.7%), with lower cone-opening temperature (45.8 0.8 degreesC) and later first fruiting (12 years) than any of our three P halepensis populations. 4 Populations of P. nigra and P. pinea did not show any fire adaptations: flowering was insignificant even 15 years after fire, and none of the cones produced were serotinous. 5 Serotinous cones represent a fire-survival strategy for P. halepensis and P. pinaster. Early flowering is also necessary for successful post-fire colonization in species or populations where crown fires are frequent. Late flowering and non-serotinous cones of P. nigra and P. pinea suggest that they may have evolved where ignition leads only to low intensity ground fires.