Negative impacts of invasive Acacia species in fragmented forests
The impact of Acacia dealbata (Fabaceae: EPPO List of Invasive Alien Plants) and Acacia melanoxylon in a fragmented forest landscape was evaluated with varying invasion levels in central Portugal. In 2023, surveys and sampling were conducted for both species in 25 sampling points. Of the 25 sampling points, nine were invaded (with a varying cover of Acacia, including A. dealbata and/or A. melanoxylon) and the remaining 16 showed no signs of invasion. An invaded site had between 5 % to 100 % cover of Acacia. At each point, data on vegetation structure, leaf litter and soil quality, and springtail (Collembola) functional structure were gathered. High levels of Acacia invasion were associated with reduced plant cover and plant species richness. As Acacia invasion intensified (higher percentage cover), there was a significant decrease in the leaf litter C/N ratio, and an increase in soil organic carbon. These Acacia induced impacts triggered cascading effects on the relationships between shrub cover, leaf litter and soil quality, and springtail functional structure. These findings showed that even low levels of Acacia invasion can alter above- and belowground dynamics. Prioritizing early intervention in areas with smaller infestations (i.e., especially in fragmented landscapes like those in central Portugal) can help prevent further spread and impacts of both A. dealbata and A. melanoxylon.
Sources
Juan-Ovejero R, Reis F, Martins da Silva P, Marchante E, Garcia F, Dias MC, Covelo F, Alves da Silva A, Freitas H, Sousa JP, Alves J (2025) Acacia invasion triggers cascading effects above- and belowground in fragmented forests. Neobiota 100, 345-369.