Plantation of coniferous trees modifies risk and size of Padus serotina (Ehrh.) Borkh. invasion - Evidence from a Rogów Arboretum case study

Density of natural regeneration of black cherry (Padus serotina) depends on distance from the propagule source. Ecological success of this species is higher in coniferous than deciduous forests. The main aim of this study was to assess the interaction between the distance from propagule source and tree stand type (coniferous, deciduous and mixed) on occurrence and density of natural regeneration of black cherry. The study was conducted on 202 experimental plots in Rogów Arboretum (Central Poland), consisting of plantations of alien and native tree species, growing on potential habitats of fertile deciduous forest. The density of natural regeneration was measured in four height classes: 0-0.5 m, 0.5-2 m, 2-5 m and over 5 m. Natural regeneration of black cherry occurred on 79 of the 202 plots, and its density varied from 0 to 25,660 ind. ha−1. The mean density of black cherry was statistically significantly higher (p < 0.001) in coniferous (1275.8 ± 374.2 ind. ha−1) than in deciduous (138.3 ± 48.3 ind. ha−1) and mixed (29.3 ± 12.3 ind. ha−1) stands. There was also a negative relationship between distance from propagule source (stand of P. serotina established in 1932 in the central part of the Arboretum) and density of natural black cherry regeneration (R2 = 0.19, p < 0.001). Tree stand type modified the relationship between distance from propagule source and probability of natural black cherry regeneration occurrence (p < 0.001), as well as density of natural regeneration (p < 0.001). The study proved that effects of propagule pressure were strongly modified by habitat features, which confirms that plantation of conifers on sites suited for deciduous forests increases the risk of P. serotina invasion.