Table of Contents Henrik Sjöman, Allan Gunnarsson, Stephan Pauleit, and Roland Bothmer Selection Approach of Urban Trees for Inner-city Environments: Learning from Nature ............. 194 Abstract. High diversity of species and genera and site adaptation are two important factors in achieving a healthy and sustainable urban tree popu- lation. This paper presents and discusses a selection procedure for the identification of trees adapted to inner city environments. The procedure is based on dendroecological studies of trees in natural habitats, with similarities in climate and site conditions as inner city environments. By study- ing trees in such habitats, firsthand information can be gained on the growth and performance of a wide range of species and genotypes. Two field studies were conducted, one in central China and another in northeast Romania and the adjoining Republic of Moldavia with the aim to identify tree species and genotypes adapted to inner city environments in the northern parts of central Europe and the adjoining milder parts of northern Europe. In total, 27 tree species were identified as specialists for warm and periodically dry habitats. Of these tree species, only four are currently used frequently or used to some extent in northern Europe, meaning that 23 other tree species identified in the case studies can be potential supple- ments for diversification of the urban tree population. Key Words. China; Dendroecology; Moldavia; Romania; Selection; Urban Environments; Urban Trees. Michael A. Arnold, Donita L. Bryan, Raul I. Cabrera, Geoffrey C. Denny, Jason J. Griffin, Jeffery K. Iles, Andrew R. King, Gary W. Knox, Leonardo Lombardini, Garry V. McDonald, Cynthia B. McKenney, D. Thayne Montague, Genhua Niu, H. Brent Pemberton, Adam L. Purnell, Larry J. Shoemake, Daniel K. Struve, and W. Todd Watson Provenance Experiments with Baldcypress, Live Oak, and Sycamore Illustrate the Potential for Selecting More Sustainable Urban Trees ................................................................................ 205 Abstract. Ecotypic, clonal, and racial variation present in tree species across their native ranges represent a largely untapped opportunity to select superior seed sources or clonal materials to withstand a variety of unique environmental stresses imposed in built environments and managed landscapes. This paper focuses on three important woody plant genera (Quercus L., Platanus L., and Taxodium Rich.) and researchers’ efforts to dis- cover superior genotypes with tolerances to environmental stresses, including alkaline soil conditions, moisture deficits, and temperature extremes. The study authors are also interested in exploiting geographic provenances and open-pollinated family selection to identify unique genotypes or populations having desirable ornamental attributes, rapid root regeneration potential, and/or desirable plant architecture. A discussion of current results, potential impacts on selection of urban forest trees for managed landscapes, and plans for future development and research are presented. Key Words. Built Environments; Managed Landscapes; Platanus occidentalis; Quercus fusiformis; Quercus virginiana; Seed Source; Taxodium distichum; Urban Trees. Bryant C. Scharenbroch and Michelle Catania Soil Quality Attributes as Indicators of Urban Tree Performance ................................................. 214 Abstract. Soil quality assessments are needed to improve a professional’s ability to manage urban soils and trees. This research was conducted to identify which soil properties are most useful for relating information on urban tree performance. In total, 48 soil properties were measured at 84 sites from five urban landscapes in the western suburbs of Chicago, Illinois, U.S. Key physical, chemical, and biological properties to be included in a minimum data set (MDS) for assessing urban soil quality were identified using statistical approaches and practical considerations. The MDS included: texture, bulk density, wet-aggregate stability, pH, electrical conductivity, soil organic matter (SOM), and particulate organic matter. The MDS was used to establish an urban soil quality index (USQI). The MDS and USQI were highly correlated with tree size attributes of height, trunk diameter, crown area, and age. Correlations between the MDS and USQI with trunk diameter growth rate, height growth rate, foliar N, and chlorophyll content were oſten significant, but less strong. Among the MDS parameters, SOM, pH, and texture appear to be the most informative measures for soil quality relat- ing to urban tree performance. Soil quality and tree performance increased logarithmically following site disturbance, with a plateau aſter 50 years. Key Words. Minimum Data Set; Organic Matter; pH, Texture; Tree Growth; Urban Site Index. Edward F. Gilman and Christine Wiese Root Pruning at Planting and Planting Depth in the Nursery Impact Root System Morphology and Anchorage .............................................................................................................................. 229 Abstract. Quercus virginiana Mill. Highrise® were planted into 10 L and then 57 L plastic nursery containers at two depths for a total of four depth combinations, and then root pruned in one of three different manners when planted into the landscape. Nursery planting depth had no impact on growth in the nursery or bending moment required to tilt trunks in the first two years following landscape plant- ing. Root pruning when planting into landscape by either method tested had no effect on growth the first two years. Number of roots circling inside the root ball was reduced by shaving or deep root ball slicing two growing seasons aſter planting. Root balls that were either sliced or shaved generated more roots in landscape soil one growing season aſter landscape planting than those that were not root pruned, which probably explained the greater bending moment required to pull trees out of the ground. Total cross-sectional root area one grow- ing season aſter landscape planting was greater on shaved trees than those not root pruned at planting. Bending moment at 20 degrees trunk tilt was best correlated with cross sectional area of roots growing straight across the periphery of the root ball and into landscape soil. Key Words. Anchorage; Circling Roots; Landscape Planting; Lateral Stability; Root Ball Shaving; Root Ball Slicing; Stability. ©2012 | International Society of Arboriculture | ISSN:1935-5297
September 2012
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