We studied the regeneration dynamics of the semi-shade-tolerant invasive tree species Prunus serotina in the understory of 7 pine stands in its introduced range for 4 y, focusing on temporal, spatial, and spatiotemporal patterns. In each 20- × 40-m study plot, we inventoried all trees and shrubs taller than 1 m, counted seedlings in 3 age-height classes (224 subplots), trapped P. serotina seed rain (84 subplots), and identified the P. serotina seed trees. The seed set, seed rain density, and seedling densities of P. serotina all varied between the years and between the study plots, but the temporal stability of the spatial regeneration patterns increased with regeneration stage. There was a clear distinction between (1) seedlings smaller than 20 cm, younger than 6 y, occurring in very high densities and (2) seedlings between 20 cm and 1 m tall, older than 6 y, showing high spatiotemporal stability. Notwithstanding the large year-to-year variation in seed input, P. serotina maintained its regeneration potential in the forest understory by building up a short-lived seedling bank. The seedling bank strategy might represent an efficient way towards site occupancy of shade-tolerant non-native species in forest understories with few shade-tolerant native species.

Nomenclature: Kartesz (1994) for the American species and Lambinon et al. (1998) for the European species.