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

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Abstract
Summary: 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. By 15 years after the fire, P. halepensis had developed a large canopy seed bank (3–100 × 104 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 °C. Cones from adult trees opened at lower temperatures than those from young trees. 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 °C) and later first fruiting (12 years) than any of our three P. halepensis populations. 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. 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.