Urban Tree Stress in Socio-Ecological Systems

Abstract

Urban trees provide crucial ecosystem services for cities, and their health impacts how effectively they provide those ecosystem services. Urban areas present stressful conditions for trees that depend on social as well as biophysical conditions. Despite their importance, patterns of non-lethal tree stress are rarely studied in cities. Although some tree care practices are effective, the influence of the underlying socio-ecological context is poorly understood. In this dissertation, I use a literature review, field data collection, and remote sensing to assess: 1) which tree care practices are effective in mediating tree stress in urban areas and what elements of the socio-ecological context impact their effectiveness 2) how tree-level characteristics, site conditions, and tree care practices correlate to street tree stress, 3) what socio-demographic characteristics and patterns of construction are associated with street tree stress across neighborhoods, and 4) how added climatic stress from drought impacts urban trees. Analysis includes two cities (Chicago and Durham), which offer contrasts in city layout, density, climate, and historical development. When examined across neighborhoods with field data, the few tree care practices examined (mulching, pruning, landscaping) do not reduce stress for urban street trees. Despite the differences between the cities studied, urban tolerant trees consistently have lower stress. In both cities planting site type and land use can influence tree stress levels. Scaled up to a regional level, tree stress is higher in areas with more new building construction and fewer renovations or additions. Drought does not appear to differentially impact trees depending on land use or nearby construction. The relationship between tree stress and urban growing conditions is visible across scales and contexts, but some of the specific relationships, including the effectiveness of tree care practices, are more context specific.