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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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-Acorn production by Quercus ilex L. ssp. ballota (Desf.) Samp. in SW Spain was assessed, and variations between years and the influence of pruning on it were examined. To this end, an experimental study was conducted at two different sites (Calañas and San Bartolomé, in the province of Huelva) where trees were subjected to traditional (light, moderate or heavy) pruning and also to a new (crown-regeneration) pruning method. Acorn yield was quantified over a period of 5 years in the Calañas plot and 4 in the San Bartolomé plot, and found to average at 95.61 ± 0.76 g DM/m 2 , which is equivalent to 6.5 ± 0.05 kg DM/tree; however, yield figures varied markedly between years depending on the particular climatic conditions. The average acorn production was correlated with the water potential in mid summer (end of July); the annual, spring and autumn rainfall; and the actual evapotranspiration for the period from September (previous year) to August. No significant differences in acorn production between traditional pruning intensities were detected; in fact, there were only hints that heavy pruning might result in decreased acorn yields. The new pruning method used, crown-regeneration, seems promising with a view to increasing acorn yield; however, it should be tested on larger sample sizes before any final conclusions can be drawn in this respect. Based on the results, the present health status of holm oaks in southwestern Spain (a result of sustained decline) and the low value of firewood -which used to be a very important source of income from pruning a few decades ago -, the authors recommend reducing the frequency and intensity of pruning in the dehesas of the study area.holm oak / acorn production / pruning / masting Résumé -Influence de la taille et des conditions climatiques sur la production de glands par le chêne vert (Quercus ilex L.) en dehesas dans le sud ouest de l'Espagne. La production de glands par Quercus ilex L. ssp. ballota (Desf.) Samp. dans le sud ouest de l'Espagne a été mesurée, et l'influence de la taille sur les variations interannuelles a été examinée. Dans ce but, une étude expérimentales a été conduite dans deux sites (Calañas et San Bartolomé dans la province de Huelva) où des arbres ont été soumis à une taille traditionnelle (légère, modérée ou forte) et aussi à une nouvelle méthode de taille (régénération de couronne). La production de glands a été quantifiée sur une période de 5 ans sur le site de Calañas et de 4 ans sur celui de San Bartolomé et était en moyenne de 95,61 ± 0,76 g de matière sèche/m 2 , ce qui équivaut à 6,5 ± 0,05 kg de matière sèche/arbre. Cependant la production a varié de façon marquée entre années en relation avec les particularités climatiques. La moyenne de production de glands était corrélée avec le potentiel hydrique au milieu de l'été (fin juillet) ; avec les précipitations annuelles, du printemps et de l'automne, et avec l'évapotranspiration pour les périodes allant de septembre (année précédente) à août. Aucune différence significative de productio...

Acorn production patterns and the annual evolution of water relations parameters of Quercus ilex ssp. ballota (Desf.) Samp. in a dehesa (an open woodland forest) subject to various soil treatments (ploughing, ploughing ? sowing, control) were studied in southwest Spain from June 2006 to December 2008. The effects of soil water holding capacity and effective soil depth on soil and plant water status and acorn production were also investigated. Water parameters showed significant differences between the ploughing treatment and the control, and there were also significant temporal differences. Xylem water potential ranged from -3.4 ± 0.1 to -0.7 ± 0.2 MPa, and cuticular transpiration was 62.4-192.9 mmol H 2 O kg -1 s -1 . Acorn production did not differ significantly according to soil treatment, and showed large intra-specific variability. Individual values ranged from 0 to 1,220 g m -2 (fresh weight). Positive relationships were found between xylem water potential, cuticular transpiration and relative water content measured at midsummer, and acorn production during the three studied years. These results suggest that climatic conditions and soil water availability have a strong influence on plant water status, and therefore on acorn development during summer. The results also reflect the ability of this species to adapt to the Mediterranean climate by preserving water during dry periods, which to a large extent can be attributed to stomatal closure at high relative water content levels, and low cuticular transpiration during these periods.

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-Eucalyptus globulus is widely used in productive exotic plantations but the expansion of these plantations is limited by low temperatures, as its cold hardening capacity is limited (0.5 to 3.0 • C). It is not well understood how nursery fertilisation affects the field performance of plants. This led us to study the effect of three mineral nutrients (N, P and K) on both plant quality and frost tolerance. The experiment comprised eight growth treatments in which a high dose (H-) or a low dose (L-) of each nutrient was applied. Nitrogen was the nutrient that determined shoot growth, new root growth after transplanting (root egress), frost tolerance and field performance. Performance was better with treatment H-N than with treatment L-N, leaf nitrogen contents being 1.53 and 0.89% respectively. The effects of phosphorus and potassium were not significant between treatments for any parameter. The exception was P which, when interacting with N, favoured root egress for the H-N treatment. It was concluded that nursery fertilisation offers a management tool for eucalyptus growers concerned with plant stock quality.field performance / frost tolerance / mineral nutrients / non-structural carbohydrates / root egress Résumé -La fertilisation en pépinière affecte la tolérance au froid et la qualité des plants bouturés d'Eucalyptus globulus Labill. Eucalyptus globulus est largement utilisé dans des plantations exotiques productives, mais l'expansion de ces plantations est limitée par les basses températures, étant donné que l'endurcissement potentiel au froid de cette espèce est limité (0,5 à 3,0 • C). On ne comprenait pas bien comment la fertilisation en pépinière pouvait affecter la performance en plantation des plants. Ceci nous a amené à étudier l'effet de trois nutriments minéraux (N, P et K) sur la qualité des plants et la résistance au froid. L'expérimentation a comporté huit traitements pour l'étude de la croissance pour lesquels une forte dose (H-) ou une faible dose (L-) de chaque nutriment a été apportée. L'azote a été le nutriment qui a déterminé la croissance de la pousse, la croissance de nouvelles racines après transplantation (émission de racines), la résistance au froid et la performance en plantation. Les performances étaient meilleures avec le traitement H-N que avec le traitement L-N, la teneur en azote des feuilles atteignant respectivement 1,53 et 0,89 %. Les effets du phosphore et du potassium n'ont été significatifs pour aucun des paramètres. L'exception a concerné le phosphore qui lorsqu'il était en interaction avec l'azote a favorisé l'émission de racines dans le traitement H-N. On conclut de cette étude que la fertilisation en pépinière offre un outil de gestion pour les producteurs d'eucalyptus confrontés au problème de la qualité des plants.performance en plantation / tolérance au froid / nutriments minéraux / hydrates de carbones non structuraux / émission de racines