Arboriculture & Urban Forestry 32(5): September 2006 217 Table 6. Mean comparisons for the tree condition rating. Species Sugar maple Silver maple Norway maple Average per tree 3.2 a 3.4 ab 3.6 b Condition rating in which 1 dead, 2 poor, 3 fair and 4 good. Means followed by a different letter are significantly different at P0.05. category and diameter class did not affect crown condition. None of the two- or three-way interactions among species, diameter, or crown loss were statistically significant for crown condition. Overall crown condition rating was 3.4 for all categories. Mean comparisons among species are pre- sented in Table 6. Crown Parameters For dead branches, significant differences (P 0.05) were found among species for small-sized branches and among the diameter categories for small-, medium-, and large-sized branches (Table 7). Larger diameter trees had more dead branches of all size categories and sugar maple contained the most dead branches and Norway maple the least. There was also a significant interaction between diameter category and maples species for large-sized branches. None of the other two- or three-way interaction among species, condition, or crown loss was statistically significant for dead branches. Overall means for the number of small-, medium-, and large- sized dead branches was 0.68, 0.24, and 0.13 branches per tree, respectively. There were no significant differences among species, con- dition, or crown loss categories or their interactions for any size hazardous or defective branches. The average overall species, diameter class, and crown condition categories for the number of small-, medium-, and large-sized hazardous branches per tree was 0.06, 0.05, and 0.03, respectively. The number of wounds with observable decay was also not sig- nificantly different for any of the categories or their interac- tions. Overall, 5.4% of the wounds had observable decay. Significant differences were found among species, diameter category, and crown loss category for the amount of wound closure (Table 8). There was also a significant species by diameter category interaction, but the three-way interaction was not significant. Overall, wound closure averaged 1.2 in per wound. Both the number of sprouts per wound and the number of sprouts per ripped branch were significantly different among species. The number of sprouts per ripped branch was also significantly different among diameter classes. None of the two- or three-way interactions was significant for sprouts per wound or per ripped branch. Over all categories, the number of sprouts per tree averaged 0.6 and 1.1 for wounds and ripped branches, respectively. Mean comparisons for sprouts are presented in Table 9. The crown parameters transparency and crown missing were both significant among species (Table 10). Crown miss- ing was also significant among crown loss categories and species by diameter class interaction. Crown dieback was not significant for any of the categories. Overall, transparency, crown missing, and dieback averaged 70%, 30%, and 7%, respectively. No other two- or three-way interaction was sig- nificant for these crown parameters. Mean comparisons for transparency and crown missing are presented in Table 9. DISCUSSION The removal rate of 26.8% over the 5 years of the study is high considering that all the study trees would be removed in less than 20 years at this rate. Federally funded removal of ice-damaged trees had been completed by the time the study was initiated and this would not have been a factor in the high removal rate. The highest rate of removal was for sugar maple and the largest diameter trees and in the highest crown loss category (Tables 4 and 5), although there was no statis- tical difference within these categories. The results indicate that urban tree managers can expect an elevated rate of re- moval after a major ice storm even after trees with the most ice damage have been removed. However, our results did not Table 7. Mean comparisons for the significant categories found in the analysis of variance on the average number of dead small-, medium-, and large-sized branches. Small dead branches Species Sugar maple Silver maple Norway maple Average per tree 1.18 a 0.59 ab 0.26 b Diameter category 15.2 to 45.7 cm (6–18 in) 45.7 to 76.2 cm (18–30 in) 76.2+ cm (30+ in) Average per tree 0.31 a 0.77 ab 1.19 b Means followed by a different letter are significantly different at P 0.05. ©2006 International Society of Arboriculture Medium dead branches Diameter category 15.2 to 45.7 cm (6–18 in) 45.7 to 76.2 cm (18–30 in) 76.2+ cm (30+ in) Average per tree 0.10 a 0.22 ab 0.55 b Large dead branches Diameter category 15.2 to 45.7 cm (6–18 in) 45.7 to 76.2 cm (18–30 in) 76.2+ cm (30+ in) Average per tree 0.02 a 0.11 ab 0.36 b
September 2006
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