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.
Laurence R. Costello, Amy Peters, and Gregory Giusti
Abstract. A 4-year study was conducted to evaluate the effects of treeshelters on the growth and survival of 3 oak species and Douglas fir growing in a Mediterranean climate. Trees were planted in irrigated and nonirrigated plots,enclosed in treeshelters or tree guards, and measured annually for height and diameter growth. In nonirrigated plots, both treeshelters and tree guards improved oak survival, but generally did not produce significant height or diameter growth increases over unprotected controls. In irrigated plots, plant growth and survival was substantially greater than that in nonirrigated plots. Irrigated trees with protection (shelters or guards) showed substantially greater survival levels than did unprotected trees. Height growth was greatest in treeshelters, and diameter growth was roughly equivalent for all irrigated treatments. Irrigated trees continued to grow when irrigation was discontinued after 3 years, and treeshelter trees exhibited little or no lean when shelters were removed. Trees without irrigation in Mediterranean climates should not be expected to exhibit growth enhancement effects from treeshelters equivalent to those found in temperate climates.
James R. Simpson and E. Gregory McPherson
Abstract. Electric utilities in California currently sponsor the planting of approximately 75,000 yard trees annually as an energy conservation measure. In this study, we evaluated the potential effects of tree shade on residential air-conditioning and heating energy use for a range of tree orientations, building insulation levels, and climate zones in California using computer simulation. Trees shading a home's west exposure produced the largest saving, both annual (kWh) and peak (kW), for all climate zones and insulation levels considered. The next largest savings were for southwest (annual and peak) and east (annual only) locations. Three trees (2 on the west, 1 on the east side) reduced annual energy use for cooling 10% to 50% (200 to 600 kWh, $30 to $110) and peak electrical use up to 23% (0.7 kW). Except in climates with little air-conditioning demand, cooling load reductions were always greater than increased heating loads associated with shade from south-side trees in winter. Air-??conditioning savings, both peak and annual, were larger in warmer climates and uninsulated buildings; percentage savings were larger in cooler climates and for more energy-efficient buildings. Recommendations are made regarding locating yard trees to maximize energy savings.
David W. Goodwin
Abstract. The creation of a street tree inventory using Geographic Information System (GIS) software can greatly enhance municipal tree management. Many different techniques were explored in an effort to map tree locations efficiently and accurately, including aerial photo interpretation, Global Positioning Systems (GPS), surveying techniques, and tree placement on existing base maps. Additionally, several different types of basemaps were tested to optimize accurate cartographic transfer of tree locations. Detailed data about tree attributes were collected in the field using a portable, preprogrammed computer so that these data would be compatible with a GIS. The spatial tree location data were joined with the tree attribute data to produce a fully functional spatial database for street tree management purposes. Based upon 2 case studies, the advantages and disadvantages of each project phase are discussed and qualified.
J. Garbaye and J.L. Churin
Abstract. By analogy with the techniques of controlled mycorrhization of forest plantations, an attempt was made to inoculate silver limes (Tilia tomentosa) with ectomycorrhizal fungi at planting on a street in Paris, France. In spite of poor colonization of the roots by the introduced symbionts (Laccaria laccata, Paxillus involutus and Cenococcum geophilum), tree growth was stimulated and yellowing of leaves in autumn was delayed. These results are discussed in terms of biology of the symbioses and practical benefit of this technique applied to ornamental trees in urban plantations.
Herbert W. Schroeder and Steven R. Ruffolo
Abstract. Residents of Downers Grove, Illinois, were surveyed about the street trees in front of their homes and in their neighborhoods. Householders' perceptions of benefits and annoyances of 8 tree species and of 5 types of neighborhood tree populations were compared. The survey assessed residents' satisfaction with the benefits and annoyance they receive from the trees; the trees' size, shape, and growth rate; and the diversity of tree species and sizes in their neighborhoods.
Mary L. Duryea, George M. Blakeslee, William G. Hubbard, Ricardo A. Vasquez
Abstract. The destructive winds of Hurricane Andrew dramatically changed the urban forest in Dade County, Florida, on August 24, 1992. Overnight, the tree canopy was replaced by a landscape of unbroken, uprooted, defoliated, and severely damaged trees. To assist communities in reforestation efforts, scientists at the University of Florida conducted a homeowner survey to determine how different tree species responded to strong winds. Native tree species, such as box leaf stopper, sabal palm gumbo limbo, and live oak were the best survivors of the winds. Other palms such as areca, cabada, and Alexander were also highly wind resistant. In general, fruit trees such as navel orange, mango, avocado, and grapefruit were severely damaged. Black olive, live oak, and gumbo limbo trees that were pruned survived the hurricane better than the unpruned trees did. Only 18% of all the trees that fell caused property damage. Hurricane-susceptible communities should consider wind resistance as one of their criteria in tree species selection.
Julian A. Dunster
Abstract. Many new housing developments are moving into forests, and the public and political pressures to retain trees are high. However, in the absence of good species profiles, hazard tree and tree retention assessments in such forests are fraught with problems. To overcome some of these, species profiles are being developed to assist arborists in knowing what is reasonable to retain and way, and to provide a more defensible basis to justify removal. The hemlock has been evaluated in detail. The findings reveal that external indicators are not sufficient to judge the internal condition of hemlocks. A preliminary species profile has been developed for the western hemlock and is now being refined.