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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. Summary1 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 × 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 ° C. 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 ° C) 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.

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Changes in leaf size, specific leaf area (SLA), transpiration and tissue water relations were studied in leaves of rooted cuttings of selected clones of Eucalyptus globulus Labill. subjected to well-watered or drought conditions in a greenhouse. Significant differences between clones were found in leaf expansion and transpiration. There was a significant clone x treatment interaction on SLA. Water stress significantly reduced osmotic potential at the turgor loss point (Pi0) and at full turgor (Pi100), and significantly increased relative water content at the turgor loss point and maximum bulk elastic modulus. Differences in tissue water relations between clones were significant only in the mild drought treatment. Among clones in the drought treatments, the highest leaf expansion and the highest increase in transpiration during the experiment were measured in those clones that showed an early and large decrease in Pi0 and Pi100.