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Timothy J. Gardner and T. Davis Sydnor

Abstract

Five species of ornamental trees were examined with an Eppley pyranometer for interception of total solar radiation between 380 nm and 1100 nm. Measurements were made at the northern dripline and expressed as percentage of shade. Trees were selected for varying forms, branch, and canopy densities. Mean percentage of shade for the fully foliaged and leafless canopies, respectively, were Pyrus calleryana ‘Chanticleer’ 75% and 43%, Acer rubrum ‘Red Sunset’ 69% and 25%, Zelkova serrata ‘Village Green’ 61% and 24%, Gymnocladus dioicus 60% and 15%, Gleditsia triacanthos inermis ‘Moraine’ 56% and 21%. No statistically significant (PSO.05) correlation was observed among solar radiation intercepted and photosynthetically active radiation (PAR) intercepted, pathlength, silhouette area, and canopy volume. Growth habit did not affect shading capacities significantly.

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Joseph R. Heckman, Uta Krogmann, and Christian A. Wyenandt

In 1988, shade tree leaves were banned from landfills and combustion facilities in New Jersey. The initial reason was that siting of new landfills and combustion facilities was difficult and existing landfill capacity had sharply decreased

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Bau-Show Lin and Yann-Jou Lin

trees also affect the energy use for heating and cooling of buildings ( Akbari et al., 1997 ; McPherson et al., 1988 ; Simpson and McPherson, 1998 ; Stec et al., 2005 ). Although several studies on the cooling effect of shade trees in temperate urban

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J. David Williams, Charles H. Gilliam, Gary J. Keever, and John Owens

Auburn Univ.'s shade tree evaluation is an ongoing study comparing a moderately diverse range of species, varieties and cultivars of larger-growing trees. Initiated in 1980, there were 250 tree selections planted in three replications located at the Piedmont Substation near Camp Hill, Ala. Among the published “fruits” of the evaluation have been critical comparisons of 10 Acer rubrum selections with respect to growth and fall color characteristics; growth rate and aesthetic characteristics of fourteen Quercus selections; growth and fireblight susceptibility of 10 Pyrus calleryana selections; and the best performing trees overall in the first 12 years of the study. The shade tree evaluation has served as an important precedent for initiation of six additional landscape tree tests in Alabama. Besides its benefits as a research project, the shade tree evaluation has provided a living laboratory for a wide range of educational audiences including landscape and nursery professionals, county extension agents, urban foresters, Master Gardeners, garden club members, and horticulture students. Knowledge gained from the shade tree evaluation has also been shared through presentations at many meetings and conferences.

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J. David Williams, Charles H. Gilliam, Gary J. Keever, and John T. Owen

The Auburn University Shade Tree Evaluation is an ongoing trial of a moderately diverse range of species, and varieties of larger-growing trees. The study was initiated in 1980 with the planting of 250 selections in three replications of three trees each, located at the Alabama Agricultural Experiment Station, Piedmont Substation in east-central Alabama. Among the fruit of the investigation have been an evaluation of 10 red maple (Acer rubrum) selections with respect to growth and fall color characteristics; a comparison of growth rate and aesthetic characteristics of 14 oak (Quercus) selections; a comparison of the growth and fireblight (Erwinia amylovora) susceptibility of 10 callery pear (Pyrus calleryana) selections; and a 12-year evaluation of the overall best performing trees. The Shade Tree Evaluation has served as a precedent for six additional landscape tree evaluations in Alabama. It has provided a living laboratory for a wide range of educational audiences including landscape and nursery professionals, county extension agents, urban foresters, Master Gardeners, garden club members, and horticulture students. Knowledge gained from the Shade Tree Evaluation has been shared through presentations at meetings and conferences.

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Roger Kjelgren

Supplemental watering of shade trees in field production nurseries is needed, even in summer-rainfall climates, to achieve maximum growth. Scheduling the timing and amount of supplemental watering makes more efficient use of financial and water resources while maintaining maximum growth. Methods of scheduling supplemental watering based on uniform canopy and rooting in production agriculture must be modified, however, for shade trees in a production setting. Nursery trees are non-uniform in canopy and rooting compared to an agricultural crop. Applying the water budget method can be effective with sprinkler systems if tree water loss and rooting depth can be properly estimated. A measure of reference evapotranspiration and a species-specific multiplier are typically used to estimate water loss. Since species diversity in a field nursery is quite high, however, estimates of both tree transpiration and rooting depth must necessarily be simplified assumptions less accurate than for a uniform agricultural crop. If supplemental water is to be applied with drip irrigation, estimates of tree transpiration and soil water depletion need to be converted to volume units with information on total tree leaf area.

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Daniel K. Struve

A method is described for producing bare-root shade tree whips in containers. Whip production is begun in February in heated greenhouses by sowing seed. Seedlings are transplanted to copper-treated containers and grown in a greenhouse until May, when they are moved outdoors and transplanted to No. 3 copper-treated containers. In October (8 months after seeding), plant heights range from 1 to 2 m. Several media have been developed that result in rapid growth, while separating readily from the root system by hand-shaking. Bare-root plants placed in refrigerated storage for 6 months and repotted, retained high survival and regrowth potential. The system combines the handling ease of bare-root stock with the high survival and regrowth potential of container stock.

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Alan Kahler and Charles Sherwood

Abstract

Thirty-five pairs of shade trees were studied to determine the relation of premature senescence and resulting early defoliation to annual growth and conditions in the upper soil about the tree. The late defoliating trees experienced more radial and linear growth over the preceding five-year period. Regression analysis of radial on linear growth within each tree group revealed near linear to linear relationships for the late defoliating trees but nonlinear relationships for the early defoliating trees. Early defoliators had higher levels of N, P, and Ca in the soil about the tree at three soil depths tested. Significant positive correlations occurred between the levels of soluble salts, N, and P; between Ca, P, and N; and between K and radial growth in the early defoliators. Significant negative correlations occurred between levels of Ca and radial and linear growth. For the late defoliators, significant positive relationships were found for levels of soluble salts, N, and Ca and between radial and linear growth, with significant negative relationships between levels of P and Ca, and between N and linear growth.

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H. G. Ponder and A. L. Kenworthy

Abstract

The effect of trickle irrigation on trunk diameter increase was studied with 4 shade tree species in 1973 and 1974. Irrigation treatments consisted of 5.7 liters per hour (2 gal/hr) and no supplemental water on sugar maple (Acer saccharum Marsh.) and honey locust (Gleditsia triacanthos L.). White ash (Fraxinus americana L. cv. Autumn Purple) treatments were no water, 1.4 liters per hour, and 2.8 liters per hour. Irrigated pin oak (Quercus palustris Muench.) trees received 5.7 liters per day at application rates of 5.7, 2.8, and 1.4 liters per hour and application time per day was 1, 2, and 4 hours respectively. Leaf analysis was performed each year.

In 1973 there was a doubling in increase in diameter of irrigated pin oak, white ash, and sugar maple with the higher flow rate per hour over that of checks. Irrigated honey locust trunk diameter increase was greater than checks. In 1974, 1 hr and 2 hr irrigated pin oak and irrigated white ash again outgrew checks but irrigated honey locust and sugar maple did not.

Leaf N and K were the only elements to show consistent changes with all species. Leaf N was lower in 1974 compared to 1973 while K was higher. Trickle irrigation did not promote any consistent significant change in nutrient composition of leaves.

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Alison A. Stoven, Hannah M. Mathers, and Daniel K. Struve

The mineral nutrition requirements and fertilizer application methods for container-grown shade tree whips are not well understood. This experiment was conducted to determine the effects of fertility method (water soluble vs. controlled release) on growth, water, and N use efficiency of four taxa [(Acer ×freemanii `Jeffersred' (Autumn Blaze® maple), Cercis canadensis L. (Eastern redbud), Malus (Mill.), `Prairifire' (Prairifire crabapple), and Quercus rubra L. (red oak)] in two production environments [outdoor gravel pad vs. a retractable roof structure (RRS)]. No single fertilizer method consistently resulted in the greatest growth. In the RRS, maple and crabapple heights, and crabapple and redbud caliper were larger when whips were fertilized with controlled-release fertilizer (CRF); outdoors, CRF resulted in taller maples and larger caliper crabapples. However, in the RRS, maple whips fertilized with water-soluble fertilizer had higher production water use efficiency than those fertilized with CRF, whereas crabapple whips had higher N use efficiency when fertilized with CRF. Nitrogen use efficiency was higher for redbud and crabapple whips fertilized with CRF than with CRF. Outside, crabapple whips fertilized with CRF had higher production water use efficiency than those fertilized with water-soluble fertilizer. There were no differences in N use efficiency attributed to fertilizer method. When averaged over fertilizer application methods, height, caliper, water, and N use efficiency were greater when whips were grown in RRS than outdoors. There were two exceptions: Maple caliper and production water use efficiency were marginally higher when whips were grown outdoors. The greater growth for whips produced in the RRS was attributed to reduced ambient and substrate temperature stress.