2018 Urban Fellow
Research Topic: Land Use Planning and Management
Faculty Advisor: Mark Ashton
Forest patch size predicts seed bank composition in urban areas
As urban areas expand around the world, understanding how to restore and maintain forests within the urban environment becomes increasingly important. Given that a comprehensive understanding of regeneration dynamics is critical to designating appropriate management interventions we ask the following: how does regeneration, vis-à-vis the buried seed bank, vary in heterogenous urban forests? And, can forest patch size be used to predict regeneration and consequent management interventions?
Vacant lots and public parks throughout New Haven, CT, USA.
We sampled buried seed banks in 131 plots distributed across three forest patch sizes ranging from large intact parks (95-126 ha), to small parks (1-19 ha), and vacant lots (.05-.65 ha). We collected soil samples from the surface mineral soil and stratified them over sand in a greenhouse over a period of 5 months to record germination.
By examining seed bank floristics in a range of forest patch sizes we found that species composition and dominance of specific functional groups shifted with patch size representing a spectrum of urbanization within just one city. Seed bank floristics in large parks more closely resembled results from seed bank studies in rural forests with over 85% native germinants on average. In contrast, vacant lots were dominated by non-native germinants and more ruderal species indicative of earlier successional stages. Seed banks in small parks were variable and in some cases were more similar to large parks or vacant lots.
Our findings suggest that large parks in urban areas may be largely self-sustaining whereas smaller parks may require more intensive management for site rehabilitation, especially in early states of succession. Furthermore, our results confirm the highly heterogeneous nature of urban forest patches and call for more systematic sampling of urban areas to capture this variation and improve management prescriptions and outcomes.