Browsing by Author "Matias, Hugo"
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- Fire effects on capsules and encapsulated seeds from Eucalyptus globulus in PortugalPublication . Santos, Patrícia dos; Matias, Hugo; Deus, Ernesto; Águas, Ana; Silva, Joaquim S.Eucalyptus globulus is native to Australia and currently one of the most cultivated hardwood species worldwide. The adaptation of E. globulus to fire-prone habitats has been linked to fire as a driver for regeneration and subsequent naturalization in Mediterranean-type regions. We studied the effect of fire on capsules and encapsulated seeds of E. globulus Labill. in the canopy and on the ground, aiming to assess the role of fire in plant recruitment in Portugal. Seed shed and capsule abscission through time were compared between scorched and non-scorched branches of living trees. Additionally, we assessed the number of capsules on the ground and the viability of encapsulated seeds in burned and unburned areas of E. globulus plantations. A complementary experiment comparing the viability of seeds from different positions in the capsule (surface vs. inner) was also carried out. Our study suggests that fire promotes the dehiscence of viable seeds from capsules in the canopy, whereas it has a destructive effect on ground capsules and seeds. We obtained an average germination of 43 % in encapsulated seeds from unburned areas, suggesting that these seeds may represent a potential propagule source for plant recruitment. This study provides experimental confirmation of the reported role of fire on seedling recruitment in E. globulus and provides new insights into the potential role of ground capsules in this process.
- Understanding the naturalization of Eucalyptus globulus in Portugal: a comparison with Australian plantationsPublication . Águas, Ana; Larcombe, Matthew J.; Matias, Hugo; Deus, Ernesto; Potts, Brad M.; Rego, Francisco C.; Silva, Joaquim S.Despite the potential utility of a biogeographical approach to understanding the naturalization of exotic species, studies using this approach are scarce. Eucalyptus globulus is an economically important Australian tree species that has become naturalized in a number of countries where it was introduced. Portugal is an ideal territory to study the naturalization of E. globulus owing to: a long introduction history, the antipodal location compared to Australia and the large cultivated area. Wildling density was assessed in 116 E. globulus plantations in central Portugal through 213 transects established along plantation borders. Boosted regression trees were used to model the influence of plantation-scale variables. Results from this survey were compared with data obtained in plantations from seven Australian regions, where a similar sampling protocol had been used. In Portugal, wildlings were more abundant in plantations that were: located in moist aspects, coppiced, with older tree stems and corresponding to intermediate site growth indexes. The overall density (127 plants ha-1) was 14.9 times higher than in the Australian estate, but this ratio was reduced to 3.1 in a more comparable subset of unburnt, first rotation plantations. A generalized linear model fitted using a dataset combining the two surveys showed that country influenced wildling density, together with plantation rotation and stem age. These results provide insights into the naturalization of a widely cultivated tree species, pointing to a fundamental role of the introduction history, possibly acting along with the biogeographical characteristics of the introduced range.