Urban forested areas are subject to the pressures of urbanization; pressures manifest as altered disturbance regimes, novel landscape structure, and increased physiological stressors which in turn can threaten the persistence and regenerative potential of urban forested areas. The soil seed bank is a potentially important mechanism for the regeneration and persistence of many ecosystems by functioning to retain species and genetic diversity in addition to having the potential to regenerate a plant community after a disturbance. However, there have been few studies that examine the role of the soil seed banks for maintaining plant communities in urban environments, and even fewer in natural forests in urban areas. If seed dynamics, such as the production of seeds, incorporation of seeds into the seed bank, or germination of seeds from the seed bank, were affected by urbanization then we would expect to see differences between the urban and rural forested areas sampled. We assessed and compared the composition of the soil seed bank, via seedling emergence, and aboveground vegetation, including all woody and herbaceous species, in three urban and three rural oak-hickory natural forested areas within the greater New York City metropolitan area. We then determined the relatedness of the soil seed bank to the aboveground vegetation to assess the role of the soil seed bank in the context of seed dynamics in urban forest systems.
Results/Conclusions
We found significant differences between the urban and rural plant community composition and abundance (p= 0.001) as well as between the above and belowground plant community composition and abundance (p= 0.001). Further, the plant community present in the soil seed bank of the urban forested areas was not similar to that of the rural forested areas, nor was it similar to the aboveground vegetation found in either the urban or rural forested areas (p= 0.001). The divergence between above and belowground species composition was expected as it has been observed in previous studies in forested natural areas of similar age. However, the divergence between both the above and belowground species composition between the urban and rural forested areas is perhaps indicative of shifting species composition of urban forested systems. Thus, there should be limited reliance on the soil seed bank for regeneration of the dominant canopy species as well as for the regeneration of the associated native understory and herbaceous species by managers of urban, natural forested areas.