ARBORICULTURE & CONTENTS URBAN FORESTRY Volume 45, No. 4, July 2019 Formerly the Journal of Arboriculture, 1975 – 2005 (Volumes 1 – 31) Shaik M.Y. Hossain, H. Christoph Stuhlinger, Matthew Olson, and Benjamin A. Babst A Comparison of Indirect Watering Devices for Benefiting Newly Transplanted Urban Trees ..... 109 Abstract. Three types of indirect watering devices were compared to evaluate their performance and to determine their benefits to newly transplanted river birch (Betula nigra) trees grown in containers with well drained compost in a controlled greenhouse experiment. Two examples of each device type were used to water trees in this study: upright bags, ring bags, and open tubs. Watering device characteristics, including purchase cost, weight, capacity, and drainage times, were measured prior to installing the devices around the trees. Tree stem heights and calipers, along with leaf coverage and leaf water potential, were measured to determine any growth or water stress differences associated with watering treatments. There was substantial vari- ation in costs and drainage times among watering devices, with ring bags being the least expensive and draining water completely during the drainage test. However, there was no evidence that watering devices benefited tree growth, leaf rating, or water stress in comparison with direct watering, with the possible exception of Treegator ring bags, which may have reduced water stress marginally. Although water release from some of the indirect water- ing devices was much slower than direct watering, water release from all of the devices was completed within ten hours, which is too rapid to reduce the frequency of watering in our experiment. The major benefits of these devices are slower release of water to the soil, with reduced operator time required, and more infiltration into the soil and root zone, which avoids the surface runoff caused by quick hose (direct) watering. Key Words. Betula nigra; Greenhouse; Indirect Watering Device; Leaf Water Potential; River Birch; Slow-Release Watering Device; Transplant- ing; Tree Growth; Urban Landscape; Water Stress. Barbora Vojáčková, Jan Tippner, Petr Horáček, Luděk Praus,Václav Sebera, and Martin Brabec Numerical Analysis of Branch Mechanical Response to Loading ................................................... 120 Abstract. Failure of a tree can be caused by a stem breakage, tree uprooting, or branch failure. While the pulling test is used for assessing the first two cases, there is no device-supported method to assess branch failure. A combination of the optical technique, pulling test, and deflection curve analysis could provide a device-supported tool for this kind of assessment. The aim of the work was to perform a structural analysis of branch response to static mechanical loading. The analyses were carried out by finite element simulations in ANSYS using beam tapered elements of elliptical cross-sections. The numerical analyses were verified by the pulling test combined with a sophisticated optical assessment of deflection evaluation. The Probabilistic Design System was used to find the parameters that influence branch mechanical response to loading considering the use of cantilever beam deflection for stability analysis. The difference in the branch’s deflection between the simulation and the experiment is 0.5% to 26%. The high variability may be explained by the variable modulus of the elasticity of branches. The finite element (FE) sensitivity analysis showed a higher significance of geometry parameters (diameter, length, tapering, elliptical cross-section) than material properties (elastic moduli). The anchorage rotation was found to be signif- icant, implying that this parameter may affect the outcome in mechanical analysis of branch behavior. The branch anchorage can influence the deflec- tion of the whole branch, which should be considered in stability assessment. Key Words. Arboriculture; Deflection Curve; Digital Image Correlation; Finite Element Analysis; Pulling Test. Ryan P. Hanavan and Molly Heuss Physiological Response of Ash Trees, spp., Infested with Emerald Ash Borer, Agrilus planipennis Fairmaire (Coleoptera: Buprestidae), to Emamectin Benzoate (Tree-Äge) Stem Injections ............................................................................................................................................ 132 Abstract. Street- and park-planted ash (Fraxinus spp.) trees infested with emerald ash borer (Agrilus planipennis Fairmaire) ranging in size from 30 to 55 cm (11.8 to 21.7 in) dbh and 10 to 20 m (32.8 to 65.6 feet) in height were measured over two sites. The first group was treated with an emamectin benzoate stem injection at 10 ml/2.54 cm dbh (0.4 g ai) in June 2014, and the second group was left as an untreated control. Chlorophyll concentration and fluorescence was measured to assess plant fitness and vitality over three summers. Trees treated with emamectin benzoate showed improvements in chlorophyll concentration and plant fitness and vitality over the course of the study with peak improvement occurring in the second year. The ©2019 International Society of Arboriculture F r axinus
July 2019
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