Investigating the Effects of Urbanization on Residual Forest Soils in Knox Co., Tennessee

As the process of urbanization advances across the country, so does the importance of urban forests, which include both trees and the soils in which they grow. Soil microbial biomass, which plays a critical role in nutrient transformation in urban ecosystems, is affected by factors such as soil type and the availability of water, carbon, and nitrogen. However, the microbial dynamics of urban forest soils remain largely unknown. A key mechanistic link between plant species diversity and ecosystem function is heterotrophic microbial communities that inhabit the soil and mediate principal processes that control ecosystem carbon (C) and nitrogen (N) cycling.

The aim of this study was to characterize residual forest patches and open fields in residential areas in the City of Knoxville. A field study was conducted along an urban-to-rural gradient in order to address the three objectives: 1.The first objective was to investigate tree species diversity and soil characteristics along an urban-to-rural gradient in residual forest patches and open fields. 2. The second objective was to investigate spatial and temporal differences in chemical, physical and biological soil characteristics along urban-to-rural gradient in residual forest patches and open fields. 3. The third objective was to utilize the chemical, physical and biological soil characteristics and tree diversity in study plots to predict residual forest patches or open field based on urban or rural location.

Determining tree species diversity and soil composition along an urban-to-rural gradient in residual forest patches and open fields it was found that tree diversity did not differ significantly for residential urban and rural plots in Knoxville, Tennessee. Biologically, there was no indication that soils were affected by tree diversity, in terms of soil microbial biomass C/N along an urban-to-rural gradient in Knoxville residential plots. Rural soils did differ physically from urban soils, cation exchange capacity (CEC) and soil moisture content (GSM). Similarly, physical soil properties such as bulk density, both urban and rural sites were negatively correlated with tree diversity. Results indicate that although the urban-rural gradient is subject to urban environmental stressors, the urban ecosystem is resilient in maintaining the ecosystem functions of more natural systems.