EUCALYPTUS GLOBULUS LABILL.REGENERATION FROM SEEDS IN PORTUGUESE MAINLAND

Publications

Fire effects on capsules and encapsulated seeds from Eucalyptus globulus in Portugal

Publication . 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.

2015-11-19Journal article

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Assessing the extent and the environmental drivers of Eucalyptus globulus wildling establishment in Portugal: results from a countrywide survey

Publication . Catry, F. X.; Moreira, F.; Deus, E.; Silva, J. S.; Águas, Ana

Tasmanian blue gum (Eucalyptus globulus) has been increasingly used in forestry outside its native range, and is nowadays one of the most important pulpwood species in the world. E. globulus has great economic importance in many countries, and in Portugal it has recently become the most widespread tree species. However, there is also an increasing concern about the potential ability of eucalypts to naturally establish from seed (wildling establishment), because of negative ecological and economic impacts this could cause. The natural establishment of this fast-growing exotic species may have undesirable consequences, but little is known about its distribution, or which are the factors influencing its occurrence. In order to investigate these issues, we characterized wildling occurrence and abundance along 3111 roadside transects adjacent to eucalypt plantations distributed throughout continental Portugal. Eucalypt wildlings were found in 60 % of the sampled transects and across all natural regions, with densities ranging from 0 to 10,000 plants ha−1 (mean = 277 plants ha−1). The potential influence of environmental variables on wildling establishment from plantations was assessed using boosted regression trees. The abundance of wildlings was found to be primarily affected by precipitation and distance from the sea (used as a surrogate of thermal amplitude), although topography, frost occurrence and soil type also played a significant role. Plant density peaked at around 1500 mm of annual precipitation and it decreased with both decreasing and increasing precipitation, reaching the lowest values below 800 mm and above 2400 mm. Eucalypt wildlings were also more abundant in areas with milder temperatures, namely closer to the sea (with lower thermal amplitude) and with lower number of frost days. Finally, plant density also seemed to be favoured in areas with intermediate elevation, higher slope and with certain soil types (namely Cambisols and Podzols). Knowing the regions with higher wildling density and understanding the factors influencing plant establishment may help managers to establish and prioritize eventual control plans in regions with higher probability of recruitment.

2015-07-12Journal article

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Understanding the naturalization of Eucalyptus globulus in Portugal: a comparison with Australian plantations

Publication . 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.

2017-03-25Journal article

Open access