Jan Pergl, Martin Vojík, Petr Petřík, Jiří Sádlo, Matěj Man and Petr Pyšek
Institute of Botany, Czech Academy of Sciences, Zámek 1, 252 43 Průhonice, Czech Republic
Ornamental plants and human made habitats are traditionally studied separately from natural or semi-natural sites. Chateau parks act as sources of new alien plants recruiting from introduced ornamentals escaping from cultivation, but these habitats can also be threatened by invasive plants. To assess the role that chateau parks play in the invasion process, we studied parks as sources of new neophytes and as an environment providing protection for already present alien species.
We present results of a survey in 98 parks in the Czech Republic, that were located in urban areas, chateaus, palace gardens and countryside parks, in various landscape and socioeconomic contexts. Our study aims at (i) providing comprehensive information on spontaneously spreading alien taxa planted in parks or arriving from their surroundings, (ii) analysing their diversity, status, frequency and abundance, (iii) correlating the species data with socioeconomic factors and management practices used in the parks, and (iv) assessing the invasion potential of the taxa.
Our results show that (i) the number of escaping invaders and their population sizes are not as high as we expected, with many cultivated taxa in the parks; (ii) the parks are threatened by many invasive plants arriving from the surrounding urban landscapes; and (iii) many parks are refugia for threatened native species and vegetation. We found 242 alien taxa spreading from ornamental plantings in the parks, seven of them were cultivars of native taxa, 21 were new spreading alien taxa for the Czech Republic, and 26 were native taxa that were part of the garden planting out of their natural area. The most abundant species was the native Hedera helix, which often also behaves expansively in its natural habitats. The most abundant alien species were the invasive neophytes, Impatiens parviflora and Robinia pseudoacacia. The most common aliens recorded in the parks comprise naturalized and invasive species, which spread from the planting in almost 70% of cases, while the corresponding figure for casual aliens was only 18%.