Table of Contents H.A. Catton, S. St. George, and W.R. Remphrey An Evaluation of Bur Oak (Quercus macrocarpa) Decline in the Urban Forest of Winnipeg, Manitoba, Canada .............................................................................22 Abstract. Winnipeg, Manitoba, Canada, has a large, indigenous population of bur oak (Quercus macrocarpa Michx.). In the 1980s, many of these trees were showing signs of decline, a disease caused by a complex of abiotic and secondary biotic stressing agents. Potential causal fac- tors were investigated by comparing various aspects of 120 bur oaks visually rated as healthy or declined based on crown dieback levels. The results indicated that many selected bur oak trees predated surrounding urban development and that declined trees were significantly older with more severe stem wounds and competition from surrounding trees than healthy specimens. Average annual growth ring widths of healthy and declined trees were similar in the early part of the 20th century. However, decline actually began decades before symptoms were noticed, coinciding with a period of intense city-wide urban development, as growth of declined trees was slower than that of healthy trees begin- ning sporadically in the 1940s and consistently from 1974 to 2001. During the early years of decline, the year-by-year separation in ring width between the two categories was significantly positively related to precipitation levels. This suggested that in wet years, declined trees may have been surrounded by unfavo able water-logged soils, possibly as a result of natural drainage patterns being impeded by urban development. Key Words. Dendrochronology; Tree Decline; Urban Development. Brian C. Kane Friction Coefficients for Arborist Ropes Passing Through Cambium Saver Rings ................................................. 31 Abstract. Friction is important in tree care operations; climbers encounter friction when ascending into, working in, and descend- ing out of a tree. Twelve commonly used climbing ropes were tested on cambium saver rings made of three different materials to deter- mine rope on ring static and kinetic friction coefficients. All ropes were tested before any field use. In addition, two ropes were tested aſter they had been used in the field for 2 years and were evaluated to determine the effect of rope wear on friction. Friction coeffi- cients varied among ropes and ring materials, and surface roughness of ring material was the best predictor of friction coefficient. Used ropes exhibited higher friction coefficients than new ropes and, in most cases, superseded the influence of surface roughness of cam- bium saver rings. Simple physical models were developed to illustrate how friction coefficients can affect different aspects of tree climb- ing. There are important implications of these results for further studies on rope friction as it relates to reducing climber fatigue. Key Words. Climbing; Friction Coefficient; Rope Friction. Patrick J. Weicherding, Chad P. Giblin, Jeffrey H. Gillman, David L. Hanson, and Gary R. Johnson Mechanical Root-Disruption Practices and Their Effect on Circling Roots of Pot-Bound Tilia Cordata Mill. and Salix Alba L. ‘Niobe’ .............................................................. 43 Abstract. Pot-bound Tilia cordata Mill. and Salix alba L. ‘Niobe’ were planted in a Waukegan silt loam soil in June 2003 at the University of Mi nesota TREE nursery in St. Paul, Minnesota. Before planting, the root balls of the container-grown plants were mechanically disrupted using one of three standard root pruning practices recommended to correct circling roots: scoring (slicing), butterfly pruning, or teasing. Root balls on the controls were leſt undisturbed. The trees were harvested in October 2004. Roots growing beyond the original root ball were counted and me sured for diameter growth to assess the effectiveness of the root pruning techniques in encouraging root growth outside of the original root ball. All root disruption treat- ments resulted in increased fibrous root growth, but no mechanical root disruption method was significantly better than root balls leſt undisturbed. Key Words. Butterfly Pruning; Circling Roots; Girdling Roots; Mechanical Root Disruption; Pot-Bound; Root Pruning; Scoring; Slicing; Teas- ing. T. Davis Sydnor, Matthew Bumgardner, and Andrew Todd The Potential Economic Impacts of Emerald Ash Borer (Agrilus planipennis) on Ohio, U.S., Communities .................................................................. 48 Abstract. A survey of 200 communities with individuals such as urban foresters who have assigned responsibilities for their urban tree resource was conducted to provide baseline data on ash density within Ohio communities. Sixty-seven communities responded, includ- ing the five largest cities in Ohio. Data represent 25% of the population of Ohio and 33% of communities surveyed. Losses in landscape value for ash trees within community boundaries were estimated to be between $0.8 (median-based) and $3.4 billion (mean-based) assum- ing the complete loss of ash resulting from the emerald ash borer (EAB), a recently introduced exotic pest of native ash species in the United States. Tree removal costs would be somewhat smaller and range between $0.7 and $2.9 billion based on reported medians and means, respectively. Tree replacement costs in Ohio communities, including streets, parks, and private properties, would range between $0.3 and $1.3 billion. In aggregate, the total losses for Ohio communities, including ash landscape losses, tree removal and replacements, are estimated to range between $1.8 and $7.6 billion for a single insect pest in a single state. The potential total costs in Ohio are esti- mated to be between $157,000 and $665,000 per 1000 residents. Communities can use these figures to begin developing contingency plans. Key Words. Agrilus planipennis; Economic Impact; Emerald Ash Borer; Fraxinus; Green Ash; White Ash. ©2007 | International Society of Arboriculture | ISSN:1935-5297
January 2007
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