Impacts of Ailanthus altissima in Mediterranean grasslands
Ailanthus altissima (Simaroubaceae - EPPO List of Invasive Alien Plants) commonly known as the tree of heaven is an invasive alien plant species in the EPPO region and native to Asia. It can invade a variety of habitats including managed and unmanaged grasslands, forests, riverbanks/canal-sides, rail/roadsides, wasteland and urban areas. Within Europe, A. altissima preferentially colonises natural Mediterranean and sub-Mediterranean areas. Further north, it colonises urban and ruderal habitats. In a study conducted in the Alta Murgia National Park (South-East Italy), the impact of the species on biodiversity in grassland was studied by comparing 17 vegetation quadrats from invaded areas with nine quadrats in nearby uninvaded areas. In six of the invaded sites, A. altissima was removed and the vegetation composition was sampled for two consecutive years. The results showed that A. altissima negatively impacted on the species composition of invaded sites, where species richness and diversity were decreased compared to the uninvaded sites. In the invaded stands, there were more ruderal and common taxa, and fewer endemic and Mediterranean specific species compared to those present in the uninvaded sites. The difference between the community composition of invaded and uninvaded quadrats was most prominent when A. altissima plants exceeded 1 m in height and 50 % coverage. Following the removal of A. altissima, the recovery of the grassland community was not completely achieved after two years, suggesting lasting impacts on the habitat. The control of A. altissima caused a change in environmental conditions as well as an increase of species richness and diversity one year after removal. However, the community composition was still different from that of uninvaded grasslands. The invasion of A. altissima into the Alta Murgia dry grasslands has resulted in a large change in the plant community and management practices should take into account the age of the invasion and restoration practices.
Sources
Terzi M, Fontaneto D, Casella F (2021) Effects of Ailanthus altissima invasion and removal on high-biodiversity Mediterranean grasslands. Environmental Management. https://doi.org/10.1007/s00267-021-01522-6