Restoration and seasonal effects on seed bank composition and diversity in urban meadows

Seed bank monitoring of planted urban greenspaces is a powerful tool to evaluate restoration efforts aimed at enhancing native biodiversity. By tracking native seed persistence and non-target species reduction, seed banks offer insight into resilience against future biological invasions. Using soil seed banks, we investigated how above-ground restoration management throughout a 16 km infrastructure corridor in Toronto (Canada) impacts seedling recruitment of native seed mix species and invasive species colonization. Soil cores were taken in spring and fall from 80 plots across nine meadow locations at two restoration stages: (1) newly-established sites receiving preparatory rototilling, cover crop and native seed application; and (2) restored sites alternating between maintenance mowing treatments. In 100 days following transplantation into greenhouse trays, a total of 11 373 seedlings representing 93 taxa of forbs, grasses, and woody plants were surveyed. Restored meadows showed 30% more species, 3 times more seeds, and 9 times the proportion of targeted native seed mix species than newly-established habitats. Spring sampling of restored plots had 0.8 times more seedlings and 1.5 times higher proportion of invasive species compared to fall. Through soil preparation and native seeding, restored sites build up native seed banks, reducing spontaneous colonization opportunities for invasive species.