Date of Degree

9-2022

Document Type

Dissertation

Degree Name

Ph.D.

Program

Earth & Environmental Sciences

Advisor

Peter Groffman

Committee Members

Karin Block

Andrew Reinmann

Morgan Grove

Subject Categories

Biodiversity | Biogeochemistry | Environmental Sciences | Forest Management | Sustainability

Keywords

Macrosystems ecology, Urban ecology, Nitrogen cycling, Carbon cycling, Novel ecosystems

Abstract

Urban growth and expansion are a major component of global environmental change, with impacts on climate, air and water quality, biodiversity, and human well-being. Forests embedded in urban landscapes are critical in mitigating these impacts at local, regional, and continental scales. However, assessing urban forests is difficult because cities are heterogenous in physical, chemical, biological, and social dimensions. This heterogeneity has constrained how urban forests are defined, and therefore, how they are studied. The objective of this dissertation is to determine how these biophysical and social factors drive ecological processes in urban forests and will address three outstanding challenges in urban ecology: 1) how do soil factors control plant community development and soil nutrient cycling in urban afforestation (New York City’s MillionTrees initiative)? 2) What are the factors that drive composition and functions of novel community assembles at the ecosystem, landscape, and regional scales? 3) What is an urban forest? Our results showed that: 1) afforestation success appears to be driven by interactions between initial site conditions that facilitate plant community establishment and development that in turn enable N accumulation and cycling, creating positive feedbacks for success 2) there are marked differences in tree community composition between interstitial and references sites in most cities, which are likely driven by the expanded species pool – native and exotic, cultivated and spontaneous – in urban areas and natural variability of inherent Nitrate availability 3) differences in species composition and plant traits characteristics between urban forest literature, residential yards, and interstitial sites, suggesting that different assessments provide different results of urban forests. These results provide a better understanding of plant community development and soil nutrient cycling in urban afforestation, the composition and functions of novel community assembles at the ecosystem, landscape, and regional scales, and how different assessments characterize urban forests within and across cities.

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