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Daniel Moya Antonio Saracino Rossella Salvatore Raffaella Lovreglio Jorge de Las Heras Vittorio Leone 《Trees - Structure and Function》2008,22(4):511-519
Pinus 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 pinecone scales under the effect of fire or dry
conditions seem related to anatomic differences and it provides seeds with an efficient protection against heat. 相似文献
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Mark Borchert Matthew Johnson David S. Schreiner Stephen B. Vander Wall 《Plant Ecology》2003,168(2):207-220
Seedling recruitment in many highly serotinous populations of Pinus coulteri on California's central coast depends almost entirely on periodic, stand-replacing fire. Compared to serotinous pines of the Mediterranean Basin, little detailed information is available on the postfire demography of California closed-cone pines, including P. coulteri. In September 1996 a wildfire burned the 760-ha American Canyon Research Natural Area (RNA). Using aerial photography, we mapped burn severity of P. coulteri-chaparral woodlands and forests within the RNA. From May to September of 1997, we also quantified seedling establishment and mortality in relation to biophysical site characteristics including fire severity. Seventy-six percent of P. coulteri forests and woodlands experienced high-severity burns, 9% moderate-severity burns, and 15% low-severity or unburned. Of the 53 plots used for seedling counts, 70% were high-severity, 26% moderate-severity, and 4% low-severity. Seedling densities 13 months postfire were low (0.21 m–2), but seedling mortality also was low (8.4%). Aerial seed bank size increased from north-facing to south-facing slopes and from high-severity to low-severity burns. Seedling recruitment was unrelated to burn severity and increased with the size of the canopy seed bank (cone density). Many seedlings established from rodent seed caches; 23% of the seedlings established in clumps from seeds cached by Dipodomys agilis, Chaetodipus californicus and Peromyscus maniculatus. Pinus coulteri seeds have low potential for dispersal by wind, but secondary dispersal by rodents moves seeds away from source trees and into neighboring chaparral. We discuss the potential importance of rodent seed caching to postfire demography of California and Mediterranean serotinous pines. 相似文献
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