Understanding variation in street tree health: an examination of urban form, socioeconomic context, and management factors

Authors: Michelle Johnson*, U.S. Forest Service, Northern Research Station, NYC Urban Field Station, Rich Hallett, U.S. Forest Service, Northern Research Station, NYC Urban Field Station, Rachel Holmes, The Nature Conservancy, Healthy Trees, Healthy Cities Program, Ben Mertz, The Nature Conservancy, Healthy Trees, Healthy Cities Program
Topics: Urban Geography, Spatial Analysis & Modeling
Keywords: tree health, urban forestry, urban form, stewardship
Session Type: Paper
Day: 4/3/2019
Start / End Time: 9:55 AM / 11:35 AM
Room: Congressional A, Omni, West
Presentation File: No File Uploaded

Urban tree canopy distribution has been widely analyzed in relation to social, environmental, and built factors, with both urban form and neighborhood-level social context affecting the amount and distribution of canopy. Less examined is which factors are associated with variation in the condition of urban trees. Tree health data are critical to understanding how best to select species to plant and to effectively manage existing trees. Here, we examine the crown health of street trees in New York, NY. Crown health data were collected for street trees along randomized 0.5-mile street segments in 2015 (Manhattan and the Bronx) and 2016 (Brooklyn); street segments were spatially stratified by overlaying a grid on the city extent. We combined measures of discoloration, defoliation, dieback, and transparency into a single stress index, through a z-score calculation (Pontius and Hallett 2014). Using GIS, we aligned stress index measures of street trees with urban form (building height, building age, sidewalk width, street width, land use), socioeconomic (race, income, education), and management factors (presence of tree guard, signs of stewardship, presence of street tree stewardship groups). Species-specific multi-level spatial models were then applied to examine the relationship between tree health and these urban form, socioeconomic, and management factors. We present the results of this analysis and discuss their implications for street tree management and urban planning.

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