Several eucalypt species are known for their capacity to massively regenerate through seeds in recently burned areas, becoming an ecological problem in regions where the species is not native. Here we study the demography and the development of highly dense Eucalyptus globulus wildling populations established one year after a fire and test two methods to control these populations. We monitored five mixed E. globulus stands across one year, in Central Portugal. We established a set of plots in each stand, with three treatments: mechanical cutting, herbicide spraying and no disturbance (control plots). Herbicide was applied in four concentrations. We tagged randomly selected plants in the control plots to monitor their growth. The initial mean wildling density was 322,000 plants ha⁻¹, the highest ever recorded in the introduced range. Wildling density was significantly dependent on the density of surrounding adult E. globulus trees. Wildling density in control plots decreased 30% in one year, although showing positive variations over time because of new recruitment. Despite seasonal growth differences, wildlings showed a high growth rate throughout the year, reaching 15.6 cm month⁻¹ in the summer. The growth rate of tagged wildings was positively affected by solar radiation and negatively affected by evapotranspiration and maximum temperature. Mechanical cutting reduced wildling density by 97% while herbicide treatment reduced density between 80% (for the lowest concentration) and 99% (for the highest concentration). Herbicide-treated plants were more likely to resprout than cut plants. Regardless of the control method adopted (cutting or herbicide), management strategies should include the follow-up of the treated areas, to detect the establishment of new recruits and resprouting.

Eucalyptus globulus Labill. stands have been expanding in protected areas (sites) of the Natura 2000 network in the Iberian Peninsula (Iberia). This expansion is mostly human-driven, but there is increasing evidence of plant recruitment and escape from cultivation areas. Therefore, it is important to assess the recruitment and invasion potential of sites and associated habitats and how future climate may change this potential. Here, we use SDMs to project current and future climatic suitability for E. globulus recruitment in Iberia and combine this suitability with local factors to rate the current recruitment potential of eucalypt stands. This potential is then extrapolated to neighbour areas in Natura 2000 sites to assess the invasion potential. The results show a wide recruitment range along coastal regions of western and northern Iberia (83,275 km²) and a northward contraction under climate change, similar to the trend projected for plantation suitability. Recruitment potential of any level was identified in 989 km², while invasion potential was identified in 878 km² across 176 Natura 2000 sites. Heathlands and riparian forests were associated with the largest recruitment and invasion potential areas. This study may help in preventing further negative impacts in protected areas and habitats already affected by E. globulus expansion.

Eucalyptus globulus Labill. is a widespread forest tree species, reported as naturalized across the introduced range, often showing abundant natural regeneration after wildfires. This paper studies a post-fire cohort of seedlings derived from a small, isolated E. globulus stand in central Portugal. The aim is to better understand the genetic dynamics and dispersal mechanisms of naturally established E. globulus populations in the introduced range. The seedling density at 55 m from adult trees was 12,000 ha⁻¹, the farthest seedling being registered at 101 m. Post-fire expansion occurred in a southward direction, in accordance with predominant wind. Seedlings had significantly lower levels of genetic diversity (Ae = 5.8.; He = 0.8) than adult trees (Ae = 6.5; He = 0.8). Crossings were strongly unbalanced, with only eight trees contributing to the sampled seedlings, and one single tree contributing to 52% of these seedlings. Moreover, the co-ancestry amongst seedlings more than doubled (from θ = 0.03 to 0.076), and the population status number was around one third of the value registered for the adult population (from Ns = 16.2 to 6.6). Despite its isolation, external pollen was detected in the stand, and appears to have travelled at least 700 m, contributing to 22% of the offspring. Overall, the seedling cohort is much less diverse than the parent trees, with expected lower resilience and persistence to environmental stresses.