Importance of Habitat Context in Modelling Risk Maps for Two Established Invasive Alien Plant Species: The Case of Ailanthus altissima and Phytolacca americana in Slovenia (Europe)

• Published in: Plants (Basel) 2024-03, Vol.13 (6), p.883
• Main Authors: de Groot, Maarten, Kozamernik, Erika, Kermavnar, Janez, Kolšek, Marija, Marinšek, Aleksander, Nève Repe, Andreja, Kutnar, Lado
• Format: Article
• Language: English
• Subjects: Ailanthus altissima; Altitude; American pokeweed; Biodiversity; Climate change; Disturbances; Extreme weather; Flowers & plants; forest disturbance; Forests; habitat suitability; Habitats; Introduced species; Invasive plants; Invasive species; Land use; Monoculture; Native species; Natural disturbance; Nonnative species; Phytolacca americana; Pine trees; Plant species; Railways; Risk levels; Sanitation; Seeds; species distribution modelling; tree of heaven; Trees; Weather
• ISSN: 2223-7747; 2223-7747
• DOI: 10.3390/plants13060883

Forests are important ecosystems that face threats from climate change and global environmental shifts, with invasive alien plant species being a significant concern. Some of these invasive species have already become established, while others are in the process of naturalisation. Although forests are a relatively stable ecosystem, extreme weather events increase their vulnerability to change, and clearings left after natural disturbances are particularly susceptible to invasion by alien plant species (IAPS). We created risk maps of two species that have spread rapidly in the last decade: American pokeweed ( ) and the tree of heaven ( ). We prepared a generalised linear model based on the occurrence data collected within the LIFE ARTEMIS project. Eleven environmental variables were used to determine habitat characteristics. We constructed two models for each species: one covering the entirety of Slovenia and the other specifically for the forested areas in Slovenia, with the latter incorporating forest-specific variables (such as forest sanitation felling and monocultures). We observed the presence of both species at lower altitudes and in close proximity to water sources. American pokeweed tends to occur nearer to railways, while the presence of the tree of heaven is associated with areas lacking carbonate parent material and influenced by land use patterns. In forested areas, the occurrence of American pokeweed is influenced by forest habitat characteristics, such as disturbances caused by extreme weather events or the prevalence of Norway spruce monocultures. In contrast, the occurrence of the tree of heaven is influenced by more general environmental variables, such as altitude and proximity to railways. Consequently, we have generated risk maps for the entirety of Slovenia and separately for forested areas, both of which indicate similar levels of risk, particularly for the tree of heaven. The risk map for American pokeweed highlights numerous vulnerable areas, especially forest edges, which are highly susceptible to invasion. Furthermore, there is a higher likelihood of this species occurring in areas that have undergone sanitation felling. This study suggests that the production of risk maps of IAPS could be improved by focussing on habitat types and taking into account habitat-specific variables. This approach could enhance the early detection and management of these invasive species.