Abstract
Although interactions between alien and native plant species are well studied, data on interactions between two co-existing alien species with respect to their invasibility are scarce. The aims of this study were (1) to evaluate three factors shaping abundance of the alien shrub species Cornus alternifolia: abundance of another alien (invasive) shrub species (Prunus serotina), type of tree stand (coniferous vs. broadleaved) and distance to propagule sources and (2) to assess the potential dispersal distance of the species studied. Densities of both species were assessed within 194 experimental plots (located in experimental plantations of trees) in Rogów Arboretum (Central Poland). P. serotina occurred on 79 and C. alternifolia on 33 of the 194 plots. The furthest distance of C. alternifolia from the propagule source was 338 m. C. alternifolia reached higher densities in coniferous than broadleaved tree stands. Density of C. alternifolia depended on tree stand type and distance from the propagule source, but did not depend on density of P. serotina. Density of C. alternifolia decreased with increasing distance from the propagule source; however, this relationship was modified by the type of tree stand: densities were lower in broadleaved than in coniferous stands. The presence of the invasive species seems to neither facilitate nor limit the dispersal distance of C. alternifolia, as these two species differ in shade tolerance. The study also provided the first information about C. alternifolia potential invasiveness, because earlier this species was noticed only as casually escaping from cultivation in Slovakia.
Highlights
Invasive species cause harmful consequences for biodiversity conservation and difficulties for management
The presence of the invasive species seems to neither facilitate nor limit the dispersal distance of C. alternifolia, as these two species differ in shade tolerance
Density of C. alternifolia decreased with the increasing distance from the propagule source, and in broadleaved stands, it was lower than in coniferous stands
Summary
Invasive species cause harmful consequences for biodiversity conservation and difficulties for management. Habitat invasibility depends on propagule pressure (Lonsdale 1999; Lockwood et al 2005; Krivanek et al 2006) This term describes availability of propagules, for example expressed as quantity of mature plants (Vanhellemont et al 2009), cultivation intensity (Pysek et al 2009, 2015), distance to the nearest fruiting plant (Jagodzinski et al 2015), or propagule quality (Sinclair and Arnott 2015). Behavior of dispersal agents may influence spread of some species—for example presence of coniferous tree stands as places for perching and defecation (Z_ ywiec et al 2013)
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