Trees in Urban Environments: How Soil Quality Impacts Tree Performance
Cities around the world are increasingly investing in reforestation and afforestation efforts to mitigate impacts from climate change and population growth. However, urban soil conditions can be unfavorable for tree growth. Street trees are widely known to suffer from poor soil quality, but there has been no comprehensive review of this topic so far. Clean soils can be transported from nonurban areas to support cities’ green projects, but this approach is not sustainable. Artificial (constructed) soils can be created from various materials and have been proposed as an alternative medium for urban tree growth, but no research has been done so far to investigate the feasibility of this approach. The focus of my dissertation is to investigate the impact of urban and constructed soil parameters on tree performance. To be more specific, I tried to figure out whether it is possible to develop a soil quality assessment model that are applicable for urban tree management, which soil parameters should be included in this model, and if it is possible to construct artificial soil for urban tree planting. This dissertation includes three chapters. Chapter 1 is a comprehensive literature review of the impacts of urban soil parameters on street tree performance. This literature review found that a limited set of soil physical and chemical factors strongly influence street tree performance, and these could form the basis for a broadly applicable soil quality assessment model that may be helpful to practitioners working with urban street tree management in many areas. Chapter 2 involves assessment of soil quality and tree performance of two capped landfills in NYC - Fountain Avenue and Pennsylvania Avenue Landfills. Analysis of tree census and soil data shows that landfill soil changed in the first 12 years of restoration. Certain species planted by the city (Quercus etc.) and naturally occurring species (Salix etc.) dominate the landfill in 2018. In addition, correlation analysis between tree density and soil parameters show that plant-available Fe and Mg might be important for tree survival. In Chapter 3, an innovative soil constructed from clean glacial outwash sediment - Clean Soil Bank (CSB) was tested as a medium for urban tree planting. This study found that CSB sediment mixed with compost can be an effective replacement for purchased topsoil for tree growth. There is a clear need for further research on approaches to mitigate soil physical and chemical factors affected by urbanization, and the development of biological solutions (e.g., trees adapted to urban conditions). This research should be a high priority as street trees provide many ecosystem services that benefit urban populations around the world.
Soil Science, Sustainability, urban soil, street tree, soil quality, tree performance, tree management
City University of New York - Graduate Center
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