Woody Vegetation and Soil Characteristics of Residential Forest Patches and Open Spaces along an Urban-to-Rural Gradient

Jennifer Franklin,Sharon R Jean-Philippe,Christopher Oswalt,Benjamin L Reichert,Mark Radosevich

doi:10.4236/ojf.2015.51010

Abstract

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. 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 to investigate tree species diversity and determine spatial and temporal soil characteristics along an urban-to-rural gradient. 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.

Highlights

IntroductionVarious non-FIA inventories such as city tree inventories have been periodically conducted almost exclusively within city limits of urban areas, but inventories on residential areas (i.e. backyard trees, small woodlots in the middle of developments, or patches of residual forest lands) are limited as is the impact these “non-forested areas” as defined by FIA standards have on cycling of elements, tree diversity and soil microbial biomass. Dwyer et al (2000) reported, from the first national assessment of urban forests within the conterminous United States, urban areas (metropolitan counties) cover 24.5% of the land and contain 74.4 billion trees
Various non-FIA inventories such as city tree inventories have been periodically conducted almost exclusively within city limits of urban areas, but inventories on residential areas are limited as is the impact these “non-forested areas” as defined by FIA standards have on cycling of elements, tree diversity and soil microbial biomass
Urban areas have doubled in size over the past 20 - 25 years; urban tree cover declined across the United States at an annual rate of about 4 million trees annually from 2001-2009 (Nowak & Greenfield, 2012)

Summary

Introduction

Various non-FIA inventories such as city tree inventories have been periodically conducted almost exclusively within city limits of urban areas, but inventories on residential areas (i.e. backyard trees, small woodlots in the middle of developments, or patches of residual forest lands) are limited as is the impact these “non-forested areas” as defined by FIA standards have on cycling of elements, tree diversity and soil microbial biomass. Dwyer et al (2000) reported, from the first national assessment of urban forests within the conterminous United States, urban areas (metropolitan counties) cover 24.5% of the land and contain 74.4 billion trees. Dwyer et al (2000) reported, from the first national assessment of urban forests within the conterminous United States, urban areas (metropolitan counties) cover 24.5% of the land and contain 74.4 billion trees. Urban areas have doubled in size over the past 20 - 25 years; urban tree cover declined across the United States at an annual rate of about 4 million trees annually from 2001-2009 (Nowak & Greenfield, 2012). Tree cover across the United States within urban areas is dynamic due to natural and anthropogenic causes. Tennessee’s urban areas have an estimated 284.1 million trees as compared 8 billion trees in forests outside urban areas across the State

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