Investigating the Invasion Mechanisms of Ailanthus altissima (Mill.) Swingle by Means of Remote Sensing, Stable Isotopes, and Soil Metagenomic Sequencing Techniques

Ailanthus altissima is a fast-growing species, originating in Asia, introduced in Europe for ornamental purposes since the second half of the 18th century. The tree of heaven is currently considered as one of the most dangerous and widespread invasive woody plant species in the Mediterranean, so as to be included in the list of invasive alien species (IAS) of European Union concern. This species shows a strong pioneering character, easily adapting to a wide range of urban, rural and forest ecosystems, and it has widely spread in temperate and Mediterranean regions of the world. The dispersal of its winged seeds at considerable distances, the ability of its root system to generate numerous suckers and progeny plants, as well as its adaptability to different soil types and water regimes, has favored the spread of the species, especially in disturbed areas and along roads. However, A. altissima threatens biodiversity in natural ecosystems through competition, native species populations reduction and local extinction, habitat modification and ecosystem degradation. Effective management and control of such IAS is needed to reduce its pressure on ecosystems biodiversity. To achieve this goal, in the frame of the CNR funded USEit project (Use of operational synergies for the integrated management of IAS in Italy), we used a multidisciplinary approach for investigating and monitoring A. altissima. We selected several pilot experimental sites across central and southern Italy, with the following aims: i) detecting and mapping the spatial distribution of this species by GIS and remote sensing; ii) investigating the mutualistic relationships between the IAS and associated mycorrhizae by means of stable isotope techniques; iii) understanding the role of microbiomes in the Evolution of Increased Competitive Capacity (EICA) of A. altissima by metagenomic sequencing analysis of bacterial and fungal communities colonizing the root system of the species. The original, although partial, results of USEit will be discussed in the frame of the current knowledge on A. altissima mechanisms of invasiveness.