The composition of urban seedbanks differed considerably from that of the established vegetation. Annuals were more abundant in the seedbank than in the vegetation, while perennials were more abundant in the vegetation. Many species were present in the seedpools and not in the vegetation, and the converse was also true. Seed dispersal and/or longevity was demonstrated by the presence of ten species, not growing in the vegetation, that emerged from the seedbanks of five or more of the six sites. In the vegetation, as in the seedbanks, introduced rather than native plants were the most common, including: bluegrass (Poa pratensis), dandelion (Taraxacum officinale), plantain (Plantago spp.), clover (Trifolium spp.), knotweeds (Polygonum spp.), and various mustards (Cruciferae). The proportion of native species varied with the degree of disturbance of the site. More native species were present in the less disturbed areas. Accessibility of seed to the sites apparently varied, although access was difficult to measure. It is clear that seedbanks are a significant factor in the early development of urban vegetation and that the resulting vegetation reduces erosion and helps to create suitable habitat for closed turf species and for taller herbs and woody plants.
Janik, L.Y. and F. Stearns. 1987. Seedbanks and vegetation of disturbed urban soils. Field Station Bulletin 20(1): 3-14.