Why Acacia melanoxylon (Australian scent/blackwood)
has become one of Chile's most troublesome tree invaders ?
Rapid expansion from plantations to wildlands
Introduced for timber and ornamental uses in 1923, A. melanoxylon has already naturalised from Coquimbo to Aysén and its climatically suitable range is still growing, making large areas of central–southern Chile vulnerable to new invasions PMC. Within protected areas such as Parque Nacional Nonguén, current densities reach 5 000–13 000 stems ha-1, forming nearly monospecific stands that dominate the canopy.
Biological traits that drive invasion
The species combines prolific sexual and vegetative reproduction. Each mature tree can release hundreds of thousands of hard-coated seeds every year; soil seed banks of ≥44 000 seeds m-2 remain >95 % viable and dormant for up to five decades, while stumps resprout vigorously after cutting or fire BioMed Central. Heat from wildfires breaks dormancy and triggers mass germination, giving A. melanoxylon a post-fire advantage over native trees and shrubs . As a nitrogen-fixing legume it enriches otherwise nutrient-poor Andisol and Ultisol forest soils, altering competitive balances and facilitating its own seedlings while discouraging the shade-tolerant native flora .
Ecological impacts
Dense aromo thickets intercept light, water and nutrients, suppressing regeneration of key canopy species such as Nothofagus obliqua and fragmenting habitat for under-storey ferns, epiphytes and fauna. Shifts in litter chemistry and accelerated nutrient cycling have been linked to changes in soil microbial communities and increased fuel loads that can modify local fire regimes . Landscape homogenisation, loss of native biodiversity and reduced ecosystem resilience are repeatedly documented consequences in the Biobío and Los Ríos regions
Dense aromo thickets intercept light, water and nutrients, suppressing regeneration of key canopy species such as Nothofagus obliqua and fragmenting habitat for under-storey ferns, epiphytes and fauna. Shifts in litter chemistry and accelerated nutrient cycling have been linked to changes in soil microbial communities and increased fuel loads that can modify local fire regimes . Landscape homogenisation, loss of native biodiversity and reduced ecosystem resilience are repeatedly documented consequences in the Biobío and Los Ríos regions
Conclusion
The combination of broad climatic tolerance, extraordinary seed longevity, vigorous vegetative regrowth, soil-altering nitrogen fixation and high stand densities means Acacia melanoxylon not only spreads quickly but also changes the very processes that allow native temperate forests to recover. These attributes—documented in Chilean field manuals and recent peer-reviewed studies—explain why the species is now classed among the country's priority invasive plants and why eradication or containment must be planned as a decades-long effort rather than a one-off intervention.