Assistant Professor of Environmental Studies Dartmouth College Hanover, NH, United States
Abstract: If the adage, “one year’s seeding–seven years’ wedding” is any indication, gardeners have long understood the implications for management of soil seed banks. Persistent soil seed banks reflect long-term vegetation history, and play an important role in determining future vegetation composition, especially following perturbations. More recently, ecologists have begun to recognize the potential of buried seed banks to elucidate trends of population and community dynamics as well as system resilience across vegetation and land use types. However, seed banks in urban systems have long been neglected in the purview of the growing field despite urban green spaces providing considerable ecological, social, and economic benefits. We sought to better understand the composition of buried seed banks in urban gardens and the relative importance of management, landscape, and demographics factors in predicting composition at the neighborhood, garden, and plot levels to elucidate implications for system resilience in urban gardens with various management regimes and objectives. To investigate seed bank composition in urban gardens, we set up a study in collaboration with the Boston Community Gardens owned by the Trustees of Reservations, non-profit land conservation and historic preservation organization in Massachusetts, and stewarded by hundreds of Bostonians across the city. We collected soil samples in late fall of 2021 from ten plots, across thirty six gardens within seven different neighborhoods (n=355). We utilized the seedling emergence method to collect seedling data at the plot level over 16 months. We found significant differences in species diversity and count data at the neighborhood, garden, and plot levels. The results of our study were largely dominated by herbaceous species, aligning with findings of other urban seed bank studies on vacant urban lots and forest patches despite major differences in management levels, size, and dominant plant communities. Our findings indicate support for the urban homogenization hypothesis as sampled urban gardens showed evidence of homogenization of composition and structure. Differences in species diversity and count are best explained by management factors, although certain landscape factors, namely garden size, also showed significant relationships with count and diversity data. Variables relating to the size, number, and diversity of trees show a relationship with count data, indicating that environmental filtering of trees may be an important variable for heliophyte herbaceous species. Our results confirm the importance of management factors in urban garden design with implications for socio-ecological resilience in urban gardens.
