A diachronic approach to assess alien plant invasion: The case study of Friuli Venezia Giulia (NE Italy)

Direct experimental methods for measuring plant invasiveness based on generative vs. vegetative reproductive mechanisms have already been proposed in the literature. In the present work, an indirect method to measure plant species invasion using historical and current data from various sources is described. This method involves a diachronic approach whereby the speed of plant invasion can be measured as the rate of new site colonisation by species over time. The study was conducted in Friuli Venezia Giulia (NE Italy). Field data, herbarium collections and data from the literature since the late 19th century were used to gather information on the presence or absence of some alien species through time, and a simple index to measure the invasion rate in the territory was developed. Results show that the diachronic approach allowed the identification of species that are generally recognised as more invasive already in other studies.