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Eucalyptus globulus Labill. regeneration from seeds in Portugal´s mainland
Publication . Águas, Ana Sofia Nunes do Carmo; Rego, Francisco Castro; Silva, Joaquim Sande
Eucalyptus globulus Labill. is a plant species native to SE Australia, Tasmania and
adjacent islands. It was introduced in Portugal in the mid-19th century. In 2005/06, it was the
most abundant tree species in 23% of the afforested area in Portugal’s mainland. Forests
dominated by this species are one of the most fire-prone forest types in Portugal. This thesis
was aimed to contribute to a better understanding of the naturalization process in Portugal’s
mainland, with a special focus on the role of fire in this process. A multiscale approach was
used to address the problem. Natural regeneration of E. globulus from seeds occurs in every
natural region of the territory and may reach high densities in some locations. Spatial
distribution of both wildling occurrence and density is not uniform on national (mainland),
regional, local, and stand scales. The existence of seed sources (reproductive trees) is of
primary importance. Climatic and soil conditions affect the broad scale distribution of this
regeneration and its performance. Site quality and forest management are fundamental on a
local scale. Fire clearly plays a relevant role, inducing seed release from burnt trees, providing
safe microsites for plant recruitment and development, and allowing for the establishment of
plants in the mid-term. Moreover, litter charring enables the early development of E. globulus in
otherwise toxic conditions. Maximum wildling densities observed were 0.3 plants m-2 and
9.9 plants m-2 inside unburnt and burnt plantations, respectively. Portuguese plantations, from a
region with nationally moderate levels of seminal regeneration, had mean wildling densities
3.1 times higher than Australian plantations, from seven regions either inside or outside the
native range. In summary, cultivated trees are able to produce offspring, which grows,
establishes and may produce seeds next to parent trees, in many parts of Portugal’s mainland.
Therefore, naturalization is in progress and widespread in this territory, and fire does facilitate it
Microsite Drivers of Natural Seed Regeneration of Eucalyptus globulus Labill. in Burnt Plantations
Publication . Águas, Ana; Matias, Hugo; Rodrigues, Abel; Bailey, Tanya; Silva, Joaquim; Rego, Francisco Castro
Fire regimes are changing in several regions of the world. In those regions, some exotic
species may be better adapted to new regimes than the native species. This study focused on identifying
the microsite characteristics associated with the occurrence of post-fire Eucalyptus globulus
regeneration from seeds, outside the species native-range. This information is important in helping
to assess the naturalization status of the species, to understand its invasion risk, and to manage
wildlings in plantations. To characterize the establishment niche, pairs of microsites (sapling presence/
absence) were sampled in four salvage-logged plantations of E. globulus two years after fire
(20 pairs/plantation). Microsites of wildlings from three size classes and control microsites were
established in one of these plantations (20 quartets) in order to characterize the recruitment niche and
to assess ontogenic niche shifts. Two post-fire wildling cohorts were identified. The first emerged
just after fire and was abundant. The second emerged after logging and was scarce, probably due to
seed limitation. First-cohort wildlings were observed in microsites characterized by a high incidence
of fire-related variables (charcoal, ash, increased soil pH and K). The aggregated distribution of
these wildlings and their association with other species may indicate the existence of facilitative
relationships and/or the exploitation of resource-rich patches. All these factors were relevant for
first-cohort persistence and likely also for its establishment and recruitment. Second-cohort wildlings
occurred in microsites where salvage-logging disturbance was evident, showing the importance of
this disturbance for its emergence. Wildling size diversity was explained by the two recruitment
events and by the asymmetrical competition between wildlings and adults. No niche shifts were
detected. The high densities of E. globulus wildlings found established in burnt plantations indicated
naturalization was in progress. The timing of major recruitment events and the phenology of the
species should be considered for monitoring this regeneration and scheduling control interventions,
if required
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Fundação para a Ciência e a Tecnologia
Programa de financiamento
3599-PPCDT
Número da atribuição
PTDC/AGR-FOR/2471/2012