Average diameter (mm) and range in diameter (in parentheses) of sycamore roots (> 3 mm [0.1 in] diameter) in the top 30 cm (12 in) of soil adjacent to sidewalks with various root barriers in two soil types.
| Treatment | Well-drained soil | Poorly drained soil |
|---|---|---|
| No sidewalk/no barrier | 7.2 a* (3–31) | 6.8 a (3–43.5) |
| Sidewalk/no barrier | 7.2 a (3–32) | 6.4 a (3–35.6) |
| Sidewalk/Biobarrier® | 5.0 ab (3–18.1) | 6.2 a (3–17.4) |
| Sidewalk/Deep Root | 6.5 ab (3–39.8) | 6.9 a (3–80) |
| Sidewalk/gravel sub-base | 4.7 b (3–7.9) | 7.0 a (3–47.4) |
| Sidewalk/polyethylene | 5.4 ab (3–13.3) | 6.4 a (3–39.4) |
| Statistical significance | ||
| Treatments | ns | |
| Soil type | ns | |
| Treatments × soil type | P < 0.04 | |
↵* Means in a column with a different letter indicate a significant difference at P < 0.05 with Duncan’s MRT. Note: All treatments had a 1.2 m (4 ft) wide sidewalk installed 0.6 m (2 ft) away except where indicated. Barriers were on same side of the sidewalk as the tree; root excavations were done at the edge of the other side of the walk.