Reproductive Possibilities of Alien Species Fraxinus pennsylvanica Marsh. in the Forest Stands of the City of Bryansk

Abstract

The invasive North American species Fraxinus pennsylvanica Marsh. has a high reproductive potential in natural and urban habitats. The species is characterized by intense seed reproduction and the active distribution of seeds. However, their germination requires quite specific conditions, which are found mainly in floodplain ecosystems and occasionally in mesophytic and xerophytic urban habitats. Intense vegetative renewal allows ash trees to linger in their habitats for a long time, including after disturbances, but it is ineffective for the rapid spread of the species and occupation of new territories. F. pennsylvanica actively penetrates into natural and seminatural communities, acts as an edifier and dominant, displaces, and (or) prevents the regeneration of species of natural flora. However, these features are not pronounced in all habitats, but mainly in river valleys, including forest cultures with a simplified structure. The possible spread of F. pennsylvanica diaspores into the river floodplains by birds and humans (randomly) is of concern, because it can lead to the mass distribution of the species with a subsequent threat to the biodiversity of river valleys.