Published by the International Society of Arboriculture.
Select a title from the list below to see an abstract of the article. For information about ordering reprints of complete articles, contact ISA at (217) 355-9411 or isa@isa-arbor.com.
By Jon C. Cooper
Abstract. As the density of development has increased in New York City and its northern suburbs over the past two decades, there has been increased concern about the preservation of trees on private land. This paper presents a snapshot of how these ordinances have developed, the present situation, and the future of this area of regulation. Many of the 41 town or villages in Westchester County, New York, have some form of tree preservation ordinance. (Westchester County is an affluent suburban area imediately north of New York City, and has seen its population more than double in the past 20 years.) Important features of these ordinances include the types of private property or subdivisions covered by the regulations, use of the concept of clear cutting protection, tree classification and coverage, tree density, and enforcement mechanisms. Three types of ordinance can be differentiated. In the first type, large lot sizes are regulated, while in the second type, there are a variety of concerns about tree size and type. These ordinances are generally too weak to substantially protect private trees. The third type of ordinance, more recent in passage (or amendment), contain sufficient detail for strong enforcement in the areas of concern. A set of model regulations that are recommended for all ordinances that control trees on private land.
By Deborah K. Kennard, Francis E. Putz, and Meg Niederhofer
Abstract. A field study was conducted to measure the predictability of tree decay based on visual assessments. Predictions made by individual arborists, tree surgeons, and forest ecologists were compared with the actual amounts and distributions of decay in ten hazardous laurel oaks (Quercus hemisphaerica) that were dissected. The mean deviations of predicted area of decay and predicted loss in strength from actual values were 0.4% and 2%, respectively. The interquartile range for predicted decay area was +12 to -15%; for strength loss it was +8 to -8%. Accuracy of the predictions improved with feedback. The results of this study suggest visual assessment can be a reliable means of predicting the internal extent of decay and hollow in potentially hazardous urban trees.
By Douglas A. Findley, Gary J. Keever, Arthur H. Chappelka, D. Joseph Eakes, and Charles H. Gilliam
Abstract Five red maple (Acer rubrum L.) cultivars 'Autumn Flame', 'Fairview Flame', 'Franksred' (Red SunsetTM), 'Northfire' and 'October Glory', and 1 Freeman maple cultivar (Acer x freemanii E. Murray 'Autumn Blaze', an interspecific cross between red maple and silver maple) were exposed to 0, 100, 200, or 300 ppb ozone for 4 hours on 2 consecutive days. Visible foliar injury, characterized as a stipple on the upper leaf surface, was observed in all ozone treatments except the control, and occurred on the oldest leaves only. 'Autumn Flame' had the least visible injury (less than 1% of the leaves injured) while 'Northfire' had the most (4% of the leaves injured). In a chronic ozone exposure experiment 3 red maple cultivars ('Autumn Flame', 'Fairview Flame', and 'October Glory'), and 1 Freeman maple cultivar ('Autumn Blaze') were exposed to sub-ambient, ambient, or twice-ambient ozone levels for 9 weeks. No visible foliar injury developed in any of the ozone treatments. No differences for plants in the 3 ozone treatments occurred for height, caliper, leaf, shoot, or root dry weight. Photosynthesis was lower for sub-ambient plants and similar for twice-ambient and ambient plants 4 weeks after treatment initiation, while at 8 weeks no differences occurred. These data indicate that red maple cultivars are relatively tolerant to elevated acute and chronic ozone exposures.
By Jason Grabosky and Nina Bassuk
Abstract. Quercus robur L. seedlings were grown in compacted stone-soil mixes known to meet engineering standards for pavement base compaction and strength. Root penetration into these materials was greatly increased in comparison to an equally compacted clay loam which was also one component of the test material. Oak root penetration in a clay loam decreased 50 % from 6 grams to 3 grams dry root weight, as the bulk density increased from 1.24 to 1.55 Mg/m3. Severe root impedance was observed when clay loam bulk densities exceeded 1.5 Mg/m3 (90 % standard AASHTO peak density), a situation produced after 20 % of the standard compaction effort was imposed on the soil profile. At the standard AASHTO peak density for the clay loam (1.67 Mg/m3), which would be the norm in a sidewalk installation, root growth was entirely stopped. In contrast, structured stone-soil mixes compacted to 100 % of their respective standard AASHTO peak densities (between 1.85 and 2.07 Mg/m3) did not restrict root penetration with mean root dry weights between 4 and 6 grams and demonstrated satisfactory bearing strength (California bearing ratios between 40 and 80).
By Larry McGillivary, Steven Wiest, and David Hensley
Abstract. Electric utilities require stringent pruning guidelines in order to deliver uninterrupted electrical service to customers, and for the safety of personnel and the public. Utility pruning operations are costly, reaching approximately one billion dollars annually in the U.S. (1). The objective of this study was to document operational aspects and needs of Kansas utility pruning programs.
By Gary W. Hickman and Ed Perry
Abstract. The multiple benefits of organic mulches in landscape environments are well documented. The few problems associated with mulch use can be minimized or avoided with proper management. For example, development of nitrogen deficiency can be reduced by the addition of small amounts of nitrogen fertilizer to the mulch. Rates of 2-3 lbs nitrogen per 100 sq ft of mulch are recommended. Another problem, particularly in the West with dry summer months, is the fire potential. Several California cities and highway departments report regular mulch fires, particularly where located near traffic, from discarded cigarettes. An inexpensive method of reducing organic mulch inflammability, by the addition of fertilizer-grade ammonium sulfate, (NH4)2SO4, has been suggested in the literature. In the 1930s, this chemical was reported by the U.S. Department of Agriculture, Forest Products Laboratory, as the least expensive flame retardant of 136 chemicals tested. The purpose of this paper is to report the results of trials to test the fire retardant abilities of various ammonium sulfate applications to organic mulches used in the landscape.