Urban domestic gardens (VII): a preliminary survey of soil seed banks

As part of a larger survey of biodiversity in private gardens in Sheffield, UK, we examined the composition and diversity of the soil seed banks in each of 56 gardens. Six soil cores from each garden revealed 2759 seedlings of 119 taxa, although the real species richness is likely to be much higher than this. By far the most abundant species were weedy natives, while the most common alien was Buddleja davidii. Seeds of perennial herbs were more abundant than hundreds of all other life forms combined. More frequent species were also more abundant, but the relationship was weak. Numbers of species in the seed bank and in the garden flora were positively but very weakly related. Seeds were quite evenly distributed between 0-5 cm and 5-10 cm soil layers, and most seeds were of species known to have persistent seed banks. Seeds of some species were largely confined to gardens in which the plant was growing, but others were not.