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

The tree of heaven (Ailanthus altissima), a pioneer plant native of Asia, was spread through the old continent since the middle of the eighteenth century. A. altissima is currently considered as one of the most dangerous and widespread alien trees in the Mediterranean region. In fact, it is listed among the invasive alien species (IAS) introduced in the European Union. A. altissima shows a pronounced adaptability to many warm-temperate envi- ronments. The dispersal of its winged seeds at consider- able distances, the ability of its root system to generate numerous suckers and progeny plants together with the capacity to cope with a number of pedological and climate conditions, fostered the species, particularly following anthropic disturbance. A. altissima constitutes a rele- vant threat for natural ecosystems because of compe- tition, reduction or local extinction of native species, habitat modification and ecosystem degradation. Effec- tive management and control of A. altissima should be addressed to preserve the ecosystems’ biodiversity. To achieve this goal, the Italian project USEit adopted a multi- disciplinary strategy of investigation and monitoring of A. altissima invasion dynamics. The project focused 17 invasion locations in order to compare the center to the south of Italy, pursuing several aims: (i) to define the inva- sion geography; (ii) to investigate possible mycorrhizal mutualisms by means of isotope ratio mass spectrom- etry (IRMS); (iii) to understand the microbiota role in the specific evolution of increased competitive ability (EICA) by using metagenomic sequencing analysis of fungal and bacterial soil biocenoses. Partial findings from USEit are shown and compared to what is currently known on A. altissima mechanisms of invasiveness.