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

Abstract

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 Electronic supplementary material The online version of this article (

Planted forests and invasive alien trees in Europe: A Code for managing existing and future plantings to mitigate the risk of negative impacts from invasions

“…plentiful seed, low herbivores/ pathogens, good germination and seedling establishment conditions), arrival of suitable symbionts (notably mycorrhizae) to aid early establishment, and climatic change to conditions more suited to the planted alien trees (Despain 2001;Engelmark et al 2001). Widespread natural establishment of Eucalyptus globulus plants in Portugal was recently documented by Águas et al (2014) and Catry et al (2015).…”

“…Fire stimulates regeneration (Gill 1997) and could increase dispersal distances, so that additional measures would probably be needed to control E. globulus spread after fires. In addition, Catry et al (2015) suggest planting sterile Eucalyptus trees and prioritizing control in regions with the highest probabilities of recruitment.…”

The ongoing naturalisation of Eucalyptus spp. in the Mediterranean Basin: new threats to native species and habitats

“…In the investigated habitats, E. camaldulensis is actively replacing native tree species, significantly altering the local plant communities and ecosystem functioning (Richardson et al 2007;Tererai et al 2013). Riparian habitats, with each flood event providing new ecological niches, appear to benefit invasive alien species over native species (Hood & Naiman 2000;Catry et al 2015). Eucalyptus camaldulensis shows a great ability to exploit disturbed areas through Flores et al (2002Flores et al ( ) 1999Flores et al ( -2001 Militello in Val di Catania (CT) Roadsides Gueli and Lo Giudice (2004) 2003 Palermo (PA) Host tree (Epiphyte) Raimondo et al (2004) 2008 Salina, Vulcano and Stromboli (ME) n.s.…”

“…Cremer 1977), there are few quantitative studies of dispersal ability and the establishment of seedlings in the secondary range. Systematic surveys of E. globulus under natural conditions have only recently shown that the species has a limited ability to invade new areas, despite possessing an outstanding resistance to wildfires and human disturbance (Catry et al 2015;Fernandes et al 2016).…”

Managing Australia’s eucalypt gene pools: assessing the risk of exotic gene flow

“…wildling establishment - Figure 5). Wildling spread from Eucalyptus plantations is receiving growing attention internationally (Ritter & Yost 2009;Silva & Marchante 2012;Calviño-Cancela & Rubido-Bará 2013;Catry et al 2015;dos Santos et al 2015). In Australia, the spread of E. globulus wildlings can be viewed as a biological invasion problem per se, but it could also lead to exotic gene flow and introgression if the established wildlings reach reproductive maturity.…”