ARBORICULTURE ARBORICULTU & CONTENTS URBAN FORESTRY Volume 38, Issue 5, September 2012 Formerly the Journal of Arboriculture, 1975 – 2005 (Volumes 1 – 31) ® www.isa-arbor.com E. Gregory McPherson and Bryant C. Scharenbroch Urban Tree Growth & Longevity: Introduction .............................................................................. 171 This special issue of Arboriculture & Urban Forestry contains a series of papers related to urban tree growth and longevity. Research and new information on urban tree growth and longevity is important for improved management of our urban trees and forests, as well as assessing their function and value. The papers in this issue were presented at the Urban Tree Growth & Longevity Conference held on September 12–13, 2011 at The Morton Arboretum (Lisle, Illinois, U.S.). This international conference brought together researchers and practitioners to discuss the current state of knowledge concerning urban tree growth and longevity. The conference covered four topic areas: 1) Descriptive studies of tree growth, longevity, and mortality, 2) Roles of tree production and sales on tree growth and longevity, 3) Roles of site design and tree selection on tree growth and longevity, and 4) Roles of tree and site management on tree growth and longevity. The objectives of the conference and these papers are to: develop collaboration among professionals and researchers to help identify important gaps in our knowledge, foster discussions about promising new methodologies, prioritize research and education needs, and outline a course of action for future research and outreach on urban tree growth and longevity. A few additional papers from the conference will be published in a special section of a future issue of this journal. ® E. Gregory McPherson and Paula J. Peper Urban Tree Growth Modeling ........................................................................................................ 172 Abstract. Selecting, locating, and managing trees to provide ecosystem services are becoming increasingly important facets of municipal and consulting forestry. The science of urban tree growth modeling is fundamental to quantifying these services. This paper describes three long- term tree growth studies conducted to evaluate tree performance because repeated measurements of the same trees produce critical data for growth model calibration and validation. Several empirical and process-based approaches to modeling tree growth are reviewed. Modeling is more advanced in the fields of forestry and pomology than in urban forestry. The USDA Forest Service’s reference city research has devel- oped over 1,800 growth equations from measurements on more than 17,000 trees in 16 cities. The database is a valuable source of informa- tion that reflects regional differences in species composition, climate, soils, site conditions, and management practices. Several examples illus- trate how differences in local climate and management practices can influence growth of a single species and the resulting value of services. Further advances in urban tree growth modeling are needed to inform the design, management, and modeling of high performing landscapes. Key Words: Allometry; Ecosystem Services; Predictive Equations; Tree Growth; Urban Forest. Robert T. Fahey, Marlin L. Bowles, and Jeanette L. McBride Origins of the Chicago Urban Forest: Composition and Structure in Relation to Presettlement Vegetation and Modern Land Use ................................................................................................ 181 Abstract. Urban forests provide important ecosystem services, but species composition and canopy structure influence provisioning of these ser- vices and long-term stability of the urban canopy. Two landscape-scale data sets (presettlement land surveys and an urban tree census) were used to explore relationships among modern land use, presettlement vegetation, and urban forest canopy structure, size structure, and composition in the Chicago, Illinois, U.S., metropolitan region. Presettlement vegetation and modern land use combined to influence urban forest composition and structure. Modern forested areas with high native species dominance, canopy cover, and structural complexity were associated with forest (rather than prairie) vegetation in the presettlement landscape. Oaks (Quercus spp.), which dominated presettlement forests and provide high ecosystem service value because of their large stature and wildlife value, were strongly associated with presettlement forest areas and modern natural areas. The Chicago region is in a transitional state where composition and structure of larger size classes is heavily tied to pre-urban vegetation. In the future, this land- scape is likely to experience a shiſt in dominance from oaks to smaller-statured, shorter-lived non-native and opportunistic species. This shiſt, along with climatic change and introduction of exotic pests, may result in an urban forest with reduced potential to provide important ecosystem services. Key Words. Canopy Structure; Chicago; Ecosystem Services; Land Use; Oak; Presettlement; Quercus; Urban Forest. ©2012 | International Society of Arboriculture | ISSN:1935-5297
September 2012
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