Seedling survival of Prunus serotina Ehrh., Quercus rubra L. and Robinia pseudoacacia L. in temperate forests of Western Poland

Abstract

Although invasive trees species spread effectively across different habitats, data on survival of their seedlings are scarce. We compared seedling survival after the first year from germination for the three most invasive tree species in temperate Europe. We also assessed the impact of light availability, parental tree stands and intra- and inter-specific competition. We studied seedlings of three invasive species: Prunus serotina Ehrh., Quercus rubra L. and Robinia pseudoacacia L., in a set of 186 study plots in W Poland over three years (2015–2018). In total, we labelled 11,135 seedlings. We assessed importance of variables using machine learning techniques. Mean seedling survival was 3.9 ± 1.2%, 12.5 ± 2.2% and 0.1 ± 0.1% for P. serotina, Q. rubra and R. pseudoacacia respectively, and was higher than for native species. Survival of Q. rubra seedlings depended mostly on intraspecific competition in understory, light availability and parental trees availability. Survival of P. serotina seedlings depended mostly on intra- and inter-specific competition, germination year (precipitation seasonality) and light availability. Our study explained that despite the high seedling densities of invasive species beneath parental tree canopies, their survival was lower than in surrounding forests. These two aspects of the establishment process (seedling abundance and survival) contribute to the dynamic equilibrium between limiting (low survival beneath maternal tree canopies) and facilitating (high seedling densities beneath maternal trees canopies) the growth of young generations of invasive tree species.