Widely-spread invasive alien tree species and their effects on plant biodiversity

Invasive alien species (IAS) are well-known for their threat to biodiversity in natural and semi-natural habitats. In the European Union a new regulation on IAS entered in force on 1 January 2015 and, therefore, this calls for awareness on such topic. Many IAS are tree species of possible concern in Europe, such as black locust (Robinia pseudoacacia L.), tree of heaven (Ailanthus altissima), as well as black cherry (Prunus serotina), and silver wattle (Acacia dealbata). These tree species invade different landscapes, mainly ranging from urban to hills and piedmont areas, and are a threat to several habitats, many of which important for biodiversity conservation. Their spread has been favored by human activities for several purposes as they can provide an array of goods and several ecosystem services. We present an overview of the invaded habitats, of the contrasting effects of invasion to plant biodiversity, and of the related management measures.