ARBORICULTURE ARBORICULTU & CONTENTS URBAN FORESTRY Volume 40, Issue 2, March 2014 Formerly the Journal of Arboriculture, 1975 – 2005 (Volumes 1 – 31) ® www.isa-arbor.com G.M. Moore Wind-Thrown Trees: Storms or Management? ..............................................................................53 Abstract. Images of wind-thrown trees make for dramatic news coverage. The implied message in most coverage is that strong winds and heavy rain are the cause of the tree failure. However, is the storm the only cause of the tree falling? Many other, and often bigger, trees did not fall. This feature article reviews some of the current literature relating to windthrow of trees. The size and characteristics of tree canopies have a profound influence of the forces that winds exert on tree trunks and roots systems, while the characteristics of tree root systems often determine whether trees fail dur- ing storms. The results of a site inspection suggest that there may be other factors, such as the history of the tree and the his- tory of management practices to which the tree has been exposed, which may contribute to its failure during a storm. Site inspections of 80 wind-thrown trees from eight different genera were conducted over a period of 20 years. The inspections ® revealed that damage to exposed lateral roots (87.5%), the loss of descending roots (88.8%), and evidence of soil compaction at the base of the tree (65%) were often coincident with windthrow. Evidence of trenching near the trunk of the tree (58.8%) and waterlog- ging of the soil around the base of the tree (56.3%) were also common correlates. The literature surveyed and the results presented not only suggest where aspects of urban tree management might be improved, but may also prove helpful to arborists assessing tree haz- ards related to possible windthrow. Inspection protocol criteria should include damaged or decayed lateral roots, the loss of descend- ing roots, evidence of site or trenching work close to the trunk, and whether trees are growing in compacted and waterlogged soil. Key words. Descending Roots; Root Damage; Tree Root Systems; Tree Management; Trees and Storm Damage; Urban Trees; Windthrow. Geoffrey H. Donovan and John Mills Environmental Justice and Factors that Influence Participation in Tree Planting Programs in Portland, Oregon, U.S. .............................................................................................................70 Abstract. Many cities have policies encouraging homeowners to plant trees. For these policies to be effective, it is impor- tant to understand what motivates a homeowner’s tree-planting decision. Researchers address this question by identifying vari- ables that influence participation in a tree-planting program in Portland, Oregon, U.S. According to the study, homeowners with street trees, and those living in older homes, are more likely to participate in the local program. Homeowners who had owned their homes for longer, and those who live in census-block groups with lower high-school graduation rates, are less likely to par- ticipate in the program. Results suggest that tree-planting programs may inadvertently exacerbate environmental inequality. Key Words. Census; Demographics; Education; Environmental Justice; Income; Oregon; Portland; Race; Urban Forestry. Jonathan M. Banks and Glynn C. Percival Failure of Foliar-Applied Biostimulants to Enhance Drought and Salt Tolerance in Urban Trees ....78 Abstract. Urban environments present an array of environmental conditions detrimental to the biology of trees. Two major problems include deicing salts, a common soil pollutant, and drought. One potential option for managing these enviro men- tal disorders may be through the application of commercially available biostimulants, as these products are reported to enhance a plant's resistance to environmental stresses. Trials used containerized stock of evergreen oak (Quercus ilex), holly (Ilex aqui- folium), rowan (Sorbus able biostimulants as aucuparia), and beech (Fagus drought and salt Tolerance; Sorbus aucuparia; Tree Physiology. protectant sylvatica) to evaluate the effectiveness of compounds. Results conclude that none of biostimulants evalu- ated in this study provided any significant degree of salt or drought damage protection compared to water-treated controls. Key Words. Drought Tolerance; Environmental Stress; Fagus sylvatica; Ilex aquifolium; Landscape Disorders; Plant Health Care; Quercus ilex; Salt seven commercially avail- the ©2014 | International Society of Arboriculture | ISSN:1935-5297
March 2014
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