Negative impacts of Ailanthus altissima in the EPPO region
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. The present study was conducted in the sub-Mediterranean region of Central Italy at altitudes between 10 and 500 m above sea level. The study set out to assess the impacts of A. altissima on the environment by comparing 19 paired sites of native forests to invaded forests. Native sites were forest habitat dominated by Quercus pubescens, Pinus nigra, and Ulmus minor and were all within 500 m of the paired invasive site. Invaded sites had A. altissima present for at least 20 years. Vegetation surveys were conducted in each site including the number of species, abundance, vegetation structure and the cover of each species. Additionally, environmental variables were collected at each site, and included soil parameters, and light penetration inside the site. A. altissima had an impact on the associated plant community where invaded stands had a higher number of annual ruderal plant species and an absence of herbaceous species commonly found in forest environments. Invaded stands had lower total nitrogen and carbon and a lower carbon/nitrogen ratio. This effect demonstrates that plant litter in the invaded stands can accelerate the nutrient cycling process which can have negative effects for understory plants. Invaded stands also altered light conditions compared to native stands, due to the dense layer of young A. altissima saplings. This effect can also have negative impacts on native plant species of forest habitats.
Montecchiari S, Tesei G, Allegrezza M (2020) Ailanthus altissima forests determine a shift in herbaceous layer richness: a paired comparison with hardwood native forest in sub-Mediterranean Europe. Plants 9(10), 1404. https://doi.org/10.3390/plants9101404