Article Figures & Data
Figures
- Figure 1.
Probability of finding a root greater than 1 cm at a sidewalk joint within 1.8 m of a tree planted in a tree lawn less than 3.5 m in width. All analyses are significant at the 95% (P = 0.05) level or greater.
- Figure 2.
Probability of finding a root greater than or equal to 1 cm at a sidewalk joint within 1.8 m of a tree planted in a tree lawn less than 3.5 m in width as predicted by years since planting. Analyses are significant at the 95% (P = 0.05) level or greater except where noted.
- Figure 3.
Probability of a root as predicted by tree lawn width for 15- to 20-cm dbh class trees. Weighted linear regression analysis (r2 = 30.8%). Linear regression not significant at a = 0.05. Binary logistic regression showed a Hosmer-Lemeshow goodness of fit of 0.992 with P < 0.001. The binary regression equation is Y = 0.654 - 0.280X.
Tables
- Table 1.
Summary data for four genera of trees detailing mean tree lawn size, mean time from planting, and number joints observed.
Genus Mean tree lawn size meters (ft) Mean time since planting (years) Number of joints observed Gleditsia 1.6 (5.3) 11.0 282 Koelreuteria 1.4 (4.6) 10.6 234 Quercus 2.3 (7.4) 9.8 384 Zelkova 2.1 (6.8) 9.0 225 All Total — — 1125 Mean 2.0 (6.5) 10.1 281 Median 1.9 (6.2) 9.0 — Std. dev. 0.5 (1.8) 3.7 — - Table 2.
Simple linear regression r2 values for the probability of roots at sidewalk joints within 1.8 m (6 ft) of tree as predicted by time since planting and trunk diameter.
Genus Adjusted r2 (dbh) Adjusted r2 (time) P-value dbh as a predictor of root problem P-value time as a predictor or root problem Gleditsia 88.7% 80.0% <0.01 0.10* Koelreuteria 61.1% 44.9% <0.01 0.06* Quercus 30.2% 38.1% 0.03 0.02 Zelkova 49.6% 54.1% 0.02 0.06* All trees 75.5% 62.1% <0.01 <0.01 ↵*Denotes model that is not significant at the 95% level.
- Table 3.
Differences in root incidence at sidewalk joints within 1.8 m of trees of four genera. The percentage of positive root probes, years since planting, number of joints observed and P-values for differences among genera.
Positive root probes raw % Years since planting Number of observations P-values for differences (binary regression) Gleditsia Zelkova Koelreuteria Quercus Gleditsia 83 5-12 212 — 0.092 0.065 <0.001 Zelkova 60 6-12* 197 0.092 — 0.806 <0.001 Koelreuteria 55 5-12 162 0.065 0.806 — <0.001 Quercus 27 5-13 * 347 <0.001 <0.001 < 0.001 — ↵*Observations not available for Zelkova at year 5 and Quercus at year 12.
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