1,721,022 research outputs found
Anatomic basis and insulation of serotinous cones in Pinus halepensis Mill.
No full textPinus halepensis Mill., a widespread, low elevation conifer common in Mediterranean Basin, shows a dual reproductive strategy: post-fire obligate seeder (from serotinous cones) and an early coloniser (from non-serotinous cones). Release of seeds encased in serotinous cones is induced either by fire (pyriscence, serotiny or bradychory) or by drying (xeriscence). Morphological differences in serotinous and non-serotinous cones in natural populations of P. halepensis in Southeastern Italy were analyzed. Relationships between tree size (diameter class) and serotiny were checked by counting and sampling serotinous and non-serotinous cones. The macro and microscopic characteristics that could affect cones’ opening were measured in sampled cones. Protection against high temperatures offered by wood scales was also evaluated by applying different temperatures and time exposures, and following the inner thermal raise. Results showed that non serotinous cones had bigger resin ducts and more separate scales. Also it was highlighted that ovuliferous scales of serotinous cones were bigger and thicker. These scales had more lamellated (multilayered) sclereid cells, and were significantly thinner with a shorter lumen diameter. Continuous temperature-monitoring heat tests inside cones showed that temperatures close to the cone axis were rather low, so seed germination was not influenced. Results confirm that serotinous cones are more compact, rigid and consistent than non-serotinous cones. These characteristics explain the lower insulation, seed protection and the ease opening of non-serotinous cones as well. In conclusion, opening mechanism of pine cone scales under the effect of fire or dry conditions seem related to anatomic differences and it provides seeds with an efficient protection against heat
Influencia de tratamientos térmicos sobre la germinación de semillas de conos serotinos y no serotinos de Pinus halepensis en el tiempo
No full textCome influiscono le alte temperature sviluppate in un incendio sui coni e sui semi di Pinus halepensis Mill.?
No full text¿CÓMO AFECTAN LAS ALTAS TEMPERATURAS A LAS PIÑAS DE PINO CARRASCO? CONSIDERACIONES PARA UNA ADECUADA GESTIÓN POST-INCENDIO
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Chapter 11 Management of threatened, high conservation value, forest hotspots under changing fire regimes.
No full textSerotiny in the Mediterranean Basin: Are Pinus halepensis Mill. cones really adapted to fire?
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Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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