The invasion of riparian forests (trees and shrubs on the banks of rivers) by species of exotic trees can be a threat to the functioning of the streams. The conclusion is from a study led by Verónica Ferreira, from the University of Coimbra (UC).
[dropcap]A[/dropcap]ccording to the research, whose results are already published in the journal Biological Reviews, acacias, which are among the most aggressive invasive species in the world, can affect streams by altering the characteristics of organic matter, the amount of water and the concentration of nutrients in the water, with consequences for communities and aquatic processes, among others.
To reach these conclusions, the team, which involved researchers from the Center for Marine and Environmental Sciences (MARE) and the Center for Functional Ecology (CFE), the Faculty of Science and Technology (FCTUC), and the Center for Studies on Geography and Spatial Planning (CEGOT), from the Faculty of Letters (FLUC), developed a model to forecast the impacts of the invasion of the hardwood forest by nitrogen-fixing species in the streams, based on the invasion of deciduous temperate forests of the Centro de Portugal by species of the genus Acacia, such as mimosa (Acacia dealbata) and Australia (Acacia melanoxylon), which are among the most aggressive invasive species in the Portuguese forest.
This model allowed us to observe that the predicted effects of invasions of nitrogen-fixing species (especially acacia trees) “include changes in the quality and quantity of water and changes in the characteristics of the entry of organic matter, for example, a decrease in the diversity of leaves entering the streams. by replacing a diverse native forest with stands of the invasive species, which in advanced stages of the invasion can completely replace the native vegetation”, points out the study’s coordinator, Verónica Ferreira.
The severity of these changes, he stresses, “will depend on the magnitude of the differences in the characteristics of native and invasive species, the extent and duration of the invasion, with stronger changes expected when the invasive species are markedly different from the native ones, and invade large areas for a long period, which can make the possibility of reversing the effects more difficult”.
The full article entitled “Invasion of temperate deciduous broadleaf forests by N-fixing tree species – consequences for stream ecosystems. Biological Reviews” can be consulted here.
