Table of Contents Henry D. Gerhold Tree Lilac (Syringa reticulata) Cultivars Tested As Street Trees: Second Report ................................................... 182 Abstract. Through the Municipal Tree Restoration Program, cooperators planted three tree lilac (Syringa reticulata) cultivars in 13 Pennsylvania and New York, U.S. communities for evaluation as street trees, comparing two in each community. Standardized measurements in years 1, 2, 3, 6, 9, and 12 revealed that ‘Ivory Silk’, ‘Regent’, and ‘Summer Snow’ grew well and remained healthy at all locations. Average heights of the cultivars in the 12th year ranged from 4.8 to 5.1 m (15.8 to 16.8 ſt). Differences in average height and crown width were small. In one community, the tallest cultivar, ‘Ivory Silk’, attained an average height of 6.4 m (21.1 ſt) in the 12th year. ‘Summer Snow’ grew more slowly in height initially, and ‘Regent’ had nar- rower crowns. Foliage health ratings were somewhat lower than those of other species in some years, probably reflecting earlier yellowing of leaves in the autumn. If the tree lilac cultivars continue to grow at the same rate, they would not grow into overhead utility wires until the 18th year or later. Key Words. ‘Ivory Silk’; Performance Testing; ‘Regent’; Street Trees; ‘Summer Snow’; Syringa reticulate; Tree Lilac. Glynn C. Percival and Gillian A. Fraser The Influence of Commercial Film-Forming Polymers on Reducing Salt Spray Injury in Evergreen Oak (Quercus ilex L.) and Laurel (Prunus laurocerasus L.) ................................. 185 Abstract. A field trial was undertaken to determine the influence of four commercially available film-forming polymers (Bond [alkyl phenyl hydroxyl polyoxyethylene], Newman Crop Spray 11E™ [paraffinic oil], Nu-Film P [poly-1-p menthene], and Spray Gard [di-1-p menthene]) on reducing salt spray injury on two woody species, evergreen oak (Quercus ilex L.) and laurel (Prunus laurocerasus L.). Irrespective of species, the film-forming polymers Nu-Film-P and Spay Gard did not provide any significant degree of protection against salt spray damage irrespec- tive of concentration (1% or 2%) applied as measured by leaf chlorophyll concentrations, photosynthetic efficiency, visual leaf necrosis, foliar sodium and chloride content, and growth (height, leaf area). The film-forming polymer Newman Crop Spray 11E™ provided only 1-week pro- tection against salt spray injury. The film-forming polymer Bond provided a significant (P < 0.05) degree of protection against salt spray injury 3 months aſter application as manifest by higher leaf chlorophyll content, photosynthetic efficiency, height and leaf area, and lower visual leaf necrosis and foliar Na and Cl content compared with nontreated controls. In conclusion, results indicate that application of a suitable film-form- ing polymer can provide a significant degree of protection of up to 3 months against salt spray injury in evergreen oak and laurel. Results also indicate that when applied at 1% or 2% solutions, no problems associated with phytotoxicity and rapid degradation on the leaf surface exist. Key Words. Antitranspirants; Carotenoids; Chlorophyll Fluorescence; Chlorophylls; English Oak; Laurel; Leaf Necrosis; Photosystem II; Sodium Chloride; Urban Trees. A.M. Shirazi and S.H. Vogel Temperature Fluctuation in Fraxinus pennsylvanica var. subintegerrima and Its Surrounding Environment ............................................................................................................................ 193 Abstract. Temperature fluctuation (TF) in an 18-year-old Fraxinus pennsylvanica var. subintegerrima and its surrounding environment was monitored using HOBO Pro temperature sensors recording every 15 min from December 2001 to February 2003 at The Morton Arbor tum, Lisle, Illinois, U.S. There were significant differences (P < 0.05) between TF in 2001, mild cold temperatures, and 2003, severe record-brea ing cold temperatures. In mid-December 2001, TF range in soil 30 cm (12 in) was 4°C (39.2°F) to 4.5°C (40.1°F), sod was 3°C (37.4°F) to 4°C (39.2°F), and soil surface was 2°C (35.6°F) to 2.5°C (36.5°F), whereas canopy and mulch ranged from −1°C (30.2°F) to 10°C (50°F). The south side of the trunk had the highest fluctuation of 1°C (33.8°F) to 14°C (57.2°F) followed primarily by the west side with occasional peaks in the east. However, the west side had the highest temperature peak in mid-June. The temperature difference between south and north sides during mid-December were approximately 7°C (44.6°F). In April, the TF inside the trunk ranged from 2°C (35.6°F) to 5.5°C (41.9°F) compared with the canopy, which varied between −0.5°C (31.1°F) and 8°C (46.4°F). The west side was 2°C (35.6°F) to 3°C (37.4°F) higher in mid-July than the south, east, and north sides. On 15 February 2003, which was the coldest day recorded, the soil 30 cm (12 in) temperature (under the mulch) reached ≈−1°C (≈30.2°F), whereas sod and soil surface were ≈−2°C (≈28.4°F). Mulch and base temperature ranged from −1°C (30.2°F) to −5°C (23°F) and −2.5°C (27.5°F) to −7.5°C (18.5°F), respectively. Root core temperature was ≈−1°C (≈30.2°F), the trunk temperature range was −2.5°C (27.5°F) to −3.5°C (25.7°F), whereas the canopy was −2.5°C (27.5°F) to −7.5°C (18.5°F). The south TF range was between −0.5°C (31.1°F) and −7.5°C (18.5°F) from midday to midnight. The TF difference between south and north sides was ≈2.5°C (≈36.5°F). This freeze and thaw of the south side during winter months has been attributed to sunscald in some trees. Based on temperature observations during the coldest and warmest week, a temperature fluctuation factor (TFF), a difference between weekly minimum and maximum temperature, was introduced. During the coldest week, the TFF for canopy to trunk was 2×, trunk to root or soil was 10×, and canopy to root or soil was 20×. During the warmest week, the TFF for canopy to trunk was 2×, trunk to root or soil was 7.5×, and canopy to root or soil was 15×. The stem water content was higher throughout the year; however, the bud water content was significantly higher when approaching budbreak in April to May. In a companion study, the effect of mulch depth on TF was reexamined showing that the temperature of mulch varies dependent on the time of year. In October, 15 cm (6 in) mulch was several degrees warmer than ground, 7.5 cm (3 in) mulch, and 30 cm (12 in) mulch (P < 0.05); how- ever, in December and February, 30 cm (12 in) of mulch was significantly warmer (P < 0.05). There are many factors other than temperature that affect tree growth and development. The dynamics of TF give a greater understanding of the role temperature plays in tree physiology as well as improving horticultural and arboricultural understanding in urban environments, resulting in improved landscape management. Key Words. Canopy; Cold Hardiness; HOBO Pro; Mulch; Root Zone; Sod; Temperature Sensor. ©2007 | International Society of Arboriculture | ISSN:1935-5297
May 2007
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