Effects of soil surfaces on tree growth and soil water potential. Growth of Cercis canadensis var. texensis and Taxodium distichum were compared in simulated 1.1 m × 1.8 m (3.5 ft × 6 ft) planting pits with bare soil to surfaces covered with paving bricks of three colors (pale blond tan, red-brown or dark charcoal) on a 5.1 cm (2 in) base of builder’s sand.
| Cercis canadensis var. texensis | Taxodium distichum | |||||||
|---|---|---|---|---|---|---|---|---|
| Soil treatment | Heightz (cm) | Trunk Diameterz (mm) | Portion of the canopy with stress symptomsy (%) | Soil water potentialx (kPa) | Predawn xylem water potentialy (MPa) | Heightz (cm) | Trunk diameterz (mm) | Root densityz (mg≅cm−3) |
| Bare soil | 235 awv | 24.8 awv | 28 cwu | −6.4 awt | −0.26 cwu | 291 awv | 70.0 awv | 1.11 awv |
| Pale blond tan bricks | 215 bc | 21.3 b | 44 ab | −5.5 bc | −0.83 a | 269 a | 71.0 a | 0.76 ab |
| Red-brown bricks | 200 c | 21.6 b | 56 a | −4.9 c | −0.48 b | 289 a | 71.3 a | 0.68 ab |
| Dark charcoal bricks | 219 b | 24.3 a | 42 b | −5.8 ab | −0.55 ab | 297 a | 68.8 a | 0.56 b |
↵zShoot and root growth measures are values from the end of the study.
↵yCanopy stress symptoms and predawn xylem water potentials are means of five sample dates during growing season.
↵xSoil water potentials are means of 14 sample dates during growing season.
↵wMeans followed by the same letters within a column are not different at P < 0.05 level using least squares means procedure.
↵vValues represent mean of 5 observations.
↵uValues represent mean of 25 observations.
↵tValues represent mean of 70 observations.