In arid and semi-arid regions where few if any trees are native, urban forests are largely human-created. Thus, we hypothesize that societal drivers, such as residents’ preferences, nursery offerings, and neighborhood socioeconomic characteristics are potentially larger drivers of urban tree community composition and diversity than environmental drivers, such as precipitation and temperature. Further, cultural norms and societal pressures may result in neighborhood cohesion that influences the structure and composition of vegetation. However, the role of neighborhoods in structuring urban vegetation patterns remains largely unstudied. We investigated patterns of urban forest structure in the Salt Lake Valley, Utah, across nine neighborhoods that varied in average household income and age of homes. To sample the urban forest, we surveyed street and residential trees as well as trees available at garden stores, including both local nurseries and national mass-merchandisers. For each species, we also looked at ecosystem service-based traits. Additionally, to better understand social drivers, we conducted social surveys and interviews of residents’ preferences for trees and their attributes, services, and disservices. Using the social and ecological datasets we tested theories about urban community assembly.
We found more tree species were offered in local nurseries compared with mass merchandiser stores, and residential trees showed more species diversity than street trees. There were significant differences among neighborhoods in street and residential tree community composition. Street tree species composition and trait diversity differed with neighborhood age, while residential tree composition, but not traits, differed with neighborhood affluence. Species richness of residential trees was positively correlated with neighborhood average household income, while species richness of street trees was negatively correlated with average age of neighborhood residences. Traits of trees differed across neighborhoods of varying age, suggesting different availability and preferences over time. Lastly, there was a positive correlation between the preferences of residents for tree attributes with the number of trees that had those attributes both in residential yards and in nursery offerings. Study results identified correlations between social variables and the structure, diversity, and attributes of the urban forest in Salt Lake Valley, demonstrating the need to better understand residents’ preferences and nursery offerings in order to understand patterns of urban forest diversity.