The impact of Sorbaria sorbifolia invasions on soil seed banks in the southern taiga of Eurasia

This study aimed to assess how the invasion of the shrub Sorbaria sorbifolia affects the soil seed bank in the urban forests of Ekaterinburg (Middle Urals, Russia). We compared species composition and abundance in the above-ground vegetation and seed banks across three forest vegetation types: those dominated by the invasive shrub S. sorbifolia, those dominated by the native shrub Rubus idaeus, and those without either species. In the presence of S. sorbifolia, the total cover of plants in the herb-dwarf shrub layer decreased by two orders of magnitude, the species richness decreased by 4-6 times, and the number of above-ground vegetation species decreased by 3-4 times. The species composition of the seed banks differed qualitatively from that of the above-ground vegetation and showed little relationship with the different vegetation types. While the species composition and richness of the seed bank remained unaltered by the S. sorbifolia invasion, its size was significantly decreased by 2.0-2.4 times. The ability to negatively affect the abundance of soil seed banks demonstrates that S. sorbifolia can be reasonably categorized as a transformer species. Therefore, this invasive plant requires special attention, as its further dispersal could have major consequences for native vegetation.