Alien plant invasions in Astroni crater, a decades-long unmanaged forest in southern Italy

Alien plant invasions in Astroni crater, a decades-long unmanaged forest in southern Italy. In this work, we studied the alien vascular flora of the forest of the Astroni crater. The mixed hardwood forest of deciduous species at the crater base have been withdrawn from management for some decades but that have not achieved yet the characteristics of a true old-growth forest. The floristic list based on field investigation and reference data comprises 20 neophytes, representing 5.4% of the whole vascular flora of the Nature Reserve. Data analysis shows that the exotic flora comprises casual (25%), naturalized (50%) and invasive (25%) aliens. The share of invasive species is related both to a low disturbance level and to good conditions of naturalness in the Astroni forest. The invasive aliens are Ailanthus altissima (Mill.) Swingle, Erigeron sumatrensis Retz., Oxalis pes-caprae L., Phytolacca americana L. and Robinia pseudoacacia L. Interfering with native plant communities, these species could alter the delicate environmental balance and affect its evolutionary dynamics.