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DECAY DEVELOPMENT AND ITS RESTRICTION
IN TREES
by R.B. Pearce
Abstract. The major hypotheses that have been proposed to explain the patterns of decay development and its restriction in the wood (xylem) of living trees are outlined briefly. The current understanding of the biochemical and physiological events that contribute to the protection of pre-existing functional sapwood is reviewed, with particular reference to the formation of reaction zones at the host-pathogen interface in Acer species, especially the European sycamore maple (Acer pseudoplatanus) in which the interactions between wood-inhabiting fungi and sapwood have been extensively investigated. Studies using conventional anatomical and biochemical approaches have been integrated with the application of advanced physical techniques (nuclear magnetic resonance [NMR] imaging, proton induced X-ray emission [PIXE] microanalysis and mapping, and electron paramagnetic resonance [EPR] spectroscopy), allowing a model describing the development and function of reaction zones in this species to be proposed. Results from other woody angiosperms indicate that in some (e.g., European beech [Fagus sylvatica]) reaction zones may be essentially similar but that in others there may be significant differences. The implications of our developing understanding of antimicrobial defense in trees on the practice of arboriculture is discussed briefly.
EFFECTIVE TREE SPECIES FOR
LOCAL AIR-QUALITY MANAGEMENT
by K. Paul Beckett, Peter Freer-Smith, and Gail Taylor
Abstract. The beneficial effect that trees have on air quality is often stated in arboricultural literature but has rarely been researched. The presented study aims to identify trees from 5 contrasting species that maximize the benefit to local air quality. Results show that all trees examined captured large quantities of airborne particulates, from the health-damaging size fractions (particle diameters of 10 to 2.5 µm, 2.5 to 1 µm, and <1 µm). Coniferous species were found to capture more particles than did broad-leaves, with pines (Pinus spp.) capturing significantly more material than cypresses (Cupresses spp.). Of the broad-leaved species, whitebeam (Sorbus aria)captured the most and poplar (Populus spp.) the least weight of particles. Trees situated close to a busy road captured significantly more material from the largest particle size fraction than those situated at a rural, background site. There was very little variation between the 2 sites in the weight of particulates from the 2 smallest particle size fractions (i.e., the fractions that are potentially the most damaging to human health).
TREES ARE NOT THE ROOT OF SIDEWALK
PROBLEMS
by T. Davis Sydnor, David Gamstetter, Joan Nichols, Bert Bishop,
Jammie Favorite, Cherelle Blazer, and Leslie Turpin
Abstract. Locations of defective sidewalk blocks in Cincinnati, Ohio, were compared to various soil complexes in the city. Soils with a percentage of repair record greater than the percentage of soil coverage were identified. The Urban-Stonelick soil complex had a low frequency of repair history. The Switzerland-Urban soil complex had a moderate record, while the Rossmoyne-Urban soil complex and the Urban-Martinsville soil complex had high frequencies of repair when compared to the records of other soil series and complexes in the city. Soil surveys categorized the Switzerland-Urban soil complex with moderate limitations for road construction and the remaining soil complexes with severe limitations. The 4 soil series were selected, and associated sidewalks were randomly surveyed to determine sidewalk failure rates. Sidewalks did not fail at higher rates where trees were present. Sidewalks greater than 20 years old failed at a higher overall percentage rate. Sidewalks less than 20 years old on the Switzerland-Urban soil complex and the Urban-Martinsville soil complex appeared more stable and less prone to failure than the Rossmoyne-Urban and Urban-Stonelick soil complexes. Sidewalks less than 5 years old were not affected by trees in any soil. A variety of problems were identified as being involved in the failure of sidewalks. It appears that trees play a minor role in sidewalk service life. Extending service life of sidewalks will require the cooperation of urban foresters, landscape architects, and engineers.
ROOT GROWTH OF QUERCUS CRASSIFOLIA,
Q. CRASSPES, AND FRAXINUS UHDEI IN 2 DIFFERENT SOIL TYPES
by Alicia Chacalo, Gary Watson, Robert Bye, Victor Ordaz, Alejandro
Aldam5, and Hector Javier Vázquez
Abstract. Abstract. Seedlings of selected tree species were grown in small benchtop rhizotrons filled with fine- and coarse-textured soils representing 2 different urban edaphic conditions in Mexico City. Bulk density was significantly higher and porosity was significantly lower in the coarse-textured soil. The maximum depth of root penetration visible behind the glass was significantly greater in the fine-textured soil for each of the 3 species after 5 months. Roots of Fraxinus uhdei penetrated deeper than roots of both Quercus crassipes and Q. crassifolia in both soils. Fraxinus uhdei root and shoot dry weight were significantly reduced in coarse-textured soil compared to the fine-textured soil, but both Quercus species were unaffected by soil type. In the fine-textured soil, F. uhdei root and shoot dry weight was significantly greater than both Quercus species, but not in the coarse-textured soil. At the end of the study, F. uhdei growing in fine-textured soil were taller than F. uhdei growing in coarse-textured soil and taller than both Quercus species in both soils, though the difference took 6 weeks longer to develop in the coarse-textured soil.
TREE WARDENS AND UTILITY ARBORISTS:
A MANAGEMENT TEAM WORKING FOR STREET TREES IN MASSACHUSETTS
by Karen D. Doherty, H. Dennis P. Ryan, and David V. Bloniarz
Abstract. Abstract. Public trees along streets and roads are often jointly managed by municipalities and electric companies. This research obtained information about community forestry programs and assessed the level of cooperation between the two management entities. The study queried electric utility staff arborists and municipal tree wardens, the arboricultural professionals in Massachusetts who are directly responsible for the planting, maintenance, and removal of street trees in urban and community forests. Results showed that the majority of communities still lack street tree inventories and management plans. Major advances in utility arboriculture have resulted in the need for trained and qualified arboricultural professionals to implement the new practices and techniques. Municipal arboriculture professionals give high ratings to the cooperation between communities and electric utilities when the private companies employ trained arborists on staff.
CRABAPPLE CULTIVARS TESTED
AS STREET TREES: SECOND REPORT
by Henry D. Gerhold
Abstract. Seventeen crabapple (Malus) cultivars planted under utility wires in 27 communities were evaluated as street trees. In most communities, 2 cultivars were alternated within each of several plots. Cooperators in the Municipal Tree Restoration Program used standardized methods to measure them annually at the end of the growing period for 3 years and periodically afterwards until the ninth year in some cases. Many differences were found in growth rate, height, crown width, and trunk diameter. Most cultivars had healthy foliage, though some injuries were caused by apple scab and several insects. Basal sprouts were common, and low branching of broader cultivars also required periodic pruning especially in confined spaces. Centurion®, Harvest Gold®, Red Jewel®, 'Spring Snow', and Sugar Tyme® are recommended as street trees based on the most extensive data. 'Adams', 'Donald Wyman', 'Prairifire', 'Red Barron', and zumi 'Calocarpa' also appear promising.
CALLERY PEAR CULTIVARS TESTED
AS STREET TREES: SECOND REPORT
by Henry D. Gerhold
Abstract. Nine Callery pear (Pyrus calleryana) cultivars were
planted under utility wires in 11 communities for evaluation as street
trees. In most communities, 2 cultivars were alternated within each of
several plots. Cooperators in the Municipal Tree Restoration Program used
standardized methods to measure them annually at the end of the growing
period for 3 years, and periodically afterwards until the ninth year in
some cases. Significant differences were found in growth rate, height,
crown width, and trunk diameter, but growth patterns and dimensions of
most cultivars that were evaluated for 9 years were similar, with some
notable exceptions. The height growth of 'Autumn Blaze' seems to have stalled
at 5.6 m (18.5 ft) 9 years after transplanting, whereas most other cultivars
exceeded 7.2 m (23.7 ft) and were still growing about 0.4 m (1.3 ft) per
year. 'Cleveland Select' and 'Whitehouse' had narrower crowns and smaller
trunks than others. All cultivars were in very good health except 'Whitehouse',
whose foliage and twigs were injured somewhat in most years by unidentified
insects and disease, possibly anthracnose or fireblight.