Composition of the soil seed bank in remnant patches of grassy woodland along an urbanization gradient in Melbourne, Australia

Abstract

Urban areas around the world are rapidly expanding, with flow-on consequences for the native plants and animals that inhabit these areas. The impacts of this urban growth are not always immediate, and in the case of the local extinction of plant species may take up to 100–150 years. Understanding how urbanization affects ecological patterns and processes may allow us to minimize the loss of species from these areas through better planning and conservation decisions. This study examined the composition of the soil seed bank in remnant patches of grassy woodland along an urbanization gradient in northern Melbourne, Australia, using an ex-situ glasshouse germination trial. A total of 108 species emerged from the soil seed bank, although a majority of the seedlings were seeds from 19 non-indigenous monocot species. Species richness per plot of emergent seedlings was best explained by average annual rainfall, rather than the degree of urbanization in the surrounding landscape. This indicates that the existing plant community may be responding to a natural productivity gradient. The persistence of 123 indigenous plant species in the existing vegetation, even when the soil seed bank is dominated by non-indigenous monocot species, suggests that these plant communities can exist within urban areas, particularly in combination with appropriate management activities that ensure the continuation of previously occurring natural processes.