ARBORICULTURE ARBORICULTU & CONTENTS URBAN FORESTRY Volume 38, Issue 4, July 2012 Formerly the Journal of Arboriculture, 1975 – 2005 (Volumes 1 – 31) ® www.isa-arbor.com Daniel W. McKenney and John H. Pedlar To Treat or Remove: An Economic Model to Assist in Deciding the Fate of Ash Trees Threatened by Emerald Ash Borer ................................................................................................ 121 Abstract. A model is presented to assist in deciding the fate of ash trees (Fraxinus spp.) threatened by the arrival of emerald ash borer (Agrilus planipennis Fairmaire) in North America. The model tracks ongoing treatment costs versus one-time costs associated with removal and replace- ment. All future values are discounted following standard economic practice. For each year over a period of interest, the net treatment gain/loss is calculated, indicating the period of time over which a homeowner would be financially ahead/behind by treating the existing ash tree. The model was populated, with values that may be expected in Canadian conditions, where treatment options are more limited than in the United States. Optional model features include property value premiums, energy savings, runoff and pollution benefits, and ongoing maintenance costs. When these extended benefits and costs are included, positive treatment gains for a medium-sized ash persist for about 17 years. Negative values can be interpreted as a “break-even existence value,” an amount a homeowner would be required to pay in order to protect their ash if various other benefit flows fail to compensate the costs. An interactive version of the model is available online (http://gmaps.nrcan.gc.ca/apm/index.php). Key Words. Agrilus planipennis; Canadian Forest Service Ash Protection Model: CFS-APM; Cost-benefit Analysis; Emerald Ash Borer; Insec- ticide Treatments; Urban Forest Management ® M.A. Grande-Ortiz, E. Ayuga-Téllez, and M.L. Contato-Carol Methods of Tree Appraisal: A Review of Their Features and Application Possibilities ................. 130 Abstract. Urban trees perform a number of basic functions related to the environment and the welfare of city dwellers (ecological, recre- ational, psychological), although their benefits are not readily quantifiable. However, in certain situations, it is essential to assign an economic value to the trees. There are currently various methods for valuing the benefits of trees and greenspaces in human settlements, including statisti- cal methods, the travel cost method, contingent valuation, the hedonic pricing method, and integrated methods. However, these methods are not used in official valuations of urban trees; in these cases, appraisal methods are used. The aim of this paper is to study the appraisal meth- ods used for their detailed features and the possibilities of their application. The main conclusion of this review is that there are a number of methods with different types of application. The best method is selected according to tree location, type of land ownership, and the availabil- ity of data. Methods with a higher degree of applicability are CTLA, a parametric method of low difficulty, and Contato, a mixed method of medium difficulty. In any case, it is advisable to increase efforts to objectify the correction index in the case of parametric and mixed methods. Key Words. Appraisal; Parametric Indexes; Urban Trees; Valuation. Gregory A. Dahle and Jason C. Grabosky Determining if Lateral Imbalance Exists in First-order Branches Leading to a Potential Development of Torsional Stress .................................................................................................. 141 Abstract. The management of urban trees requires an ability to appraise the stability of trees to select where and when a maintenance task is required to increase the functionally useful period of the tree. Torsion is oſten ignored during static bending trials and the goal of this study was to determine if first-order branches on open grown trees are laterally balanced. It is not known if lateral branch develop- ment leads to a parent branch that is evenly balanced. Second-order branch mass and center of gravity were measured and used to estimate the load acting on first-order branches. It appears that development can lead to imbalance in branches, because more than 60% of the first- order branches were imbalanced. Furthermore, 80% of the first-order branches in this specific study had more loading to the leſt side of the branch. Researchers should consider whether it is appropriate to ignore torsion when predicting how branches will behave during load- ing exercises. Additionally, the data suggests that it is possible to develop a strong predictive equation between branch length and the cen- ter of gravity (r2 = 95%) which, tied with predicted branch mass, could be useful when modeling self-loading and later balance in branches. Key Words. Biomechanics; Branches; Center of Gravity; Mass; Stress, Tilia cordata; Torsion. ©2012 | International Society of Arboriculture | ISSN:1935-5297
July 2012
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