Invasions of alien woody plant taxa across a cluster of villages neighbouring the Mlyňany Arboretum (SW Slovakia)

Ornamental plantations in cities and particularly botanical gardens and arboreta are rich sources of alien flora. Mlyňany Arboretum, established in 1892, cultivates 1049 non-native woody plant species on the area of 67 ha. In this work we answered following questions: 1. How many taxa are spontaneously spreading in the arboretum and how is the spreading intensity related to their ecological demands and reproduction traits? 2. How many taxa appear behind the fence? 3. How far from the arboretum they can get? 4. Do private gardens and historical aristocratic park in the studied village cluster contribute to species escapes from culture? 5. Which from the widely spread taxa can represent future risk of invasiveness on the national level? We found that about one tenth of taxa spread across the arboretum (particularly Cotoneaster spp., Prunus laurocerasus, P. serotina and Quercus rubra) and number of their seedlings corresponded only with the mother plant number. Almost one third of these species left the arboretum and their seedlings were observed in distance up to 500 m from the village (mainly Mahonia aquifolium, P. serotina). Private gardens were a large source of Juglans regia seedlings, frequency of which decreased with the distance from villages (no species escaped from the historical park). Weed risk assessment revealed potential invasion danger only for Amorpha fruticosa.